CD200 is overexpressed in the pancreatic tumor microenvironment and predictive of overall survival

Pancreatic cancer is an aggressive disease with a 5 year survival rate of 13%. This poor survival is attributed, in part, to limited and ineffective treatments for patients with metastatic disease, highlighting a need to identify molecular drivers of pancreatic cancer to target for more effective treatment. CD200 is a glycoprotein that interacts with the receptor CD200R and elicits an immunosuppressive response. Overexpression of CD200 has been associated with differential outcomes, depending on the tumor type. In the context of pancreatic cancer, we have previously reported that CD200 is expressed in the pancreatic tumor microenvironment (TME), and that targeting CD200 in murine tumor models reduces tumor burden. We hypothesized that CD200 is overexpressed on tumor and stromal populations in the pancreatic TME and that circulating levels of soluble CD200 (sCD200) have prognostic value for overall survival. We discovered that CD200 was overexpressed on immune, stromal, and tumor populations in the pancreatic TME. Particularly, single-cell RNA-sequencing indicated that CD200 was upregulated on inflammatory cancer-associated fibroblasts. Cytometry by time of flight analysis of PBMCs indicated that CD200 was overexpressed on innate immune populations, including monocytes, dendritic cells, and monocytic myeloid-derived suppressor cells. High sCD200 levels in plasma correlated with significantly worse overall and progression-free survival. Additionally, sCD200 correlated with the ratio of circulating matrix metalloproteinase (MMP) 3: tissue inhibitor of metalloproteinase (TIMP) 3 and MMP11/TIMP3. This study highlights the importance of CD200 expression in pancreatic cancer and provides the rationale for designing novel therapeutic strategies that target this protein.

Activation of the CD200/CD200R1 axis improves cognitive impairment by enhancing hippocampal neurogenesis via suppression of M1 microglial polarization and neuroinflammation in hypoxic-ischemic neonatal rats

Following hypoxic-ischemic brain damage (HIBD), there is a decline in cognitive function; however, there are no effective treatment strategies for this condition in neonates. This study aimed to evaluate the role of the cluster of differentiation 200 (CD200)/CD200R1 axis in cognitive function following HIBD using an established model of HIBD in postnatal day 7 rats. Western blotting analysis was conducted to evaluate the protein expression levels of CD200, CD200R1, proteins associated with the PI3K/Akt-NF-κB pathway, and inflammatory factors such as TNF-α, IL-1β, and IL-6 in the hippocampus. Additionally, double-immunofluorescence labeling was utilized to evaluate M1 microglial polarization and neurogenesis in the hippocampus. To assess the learning and memory function of the experimental rats, the Morris water maze (MWM) test was conducted. HIBDleads to a decrease in the expression of CD200 and CD200R1 proteins in the neonatal rat hippocampus, while simultaneously increasing the expression of TNF-α, IL-6, and IL-1β proteins, ultimately resulting in cognitive impairment. The administration of CD200Fc, a fusion protein of CD200, was found to enhance the expression of p-PI3K and p-Akt, but reduce the expression of p-NF-κB. Additionally, CD200Fc inhibited M1 polarization of microglia, reduced neuroinflammation, improved hippocampal neurogenesis, and mitigated cognitive impairment caused by HIBD in neonatal rats. In contrast, blocking the interaction between CD200 and CD200R1 with the anti-CD200R1 antibody (CD200R1 Ab) exerted the opposite effect. Furthermore, the PI3K specific activator, 740Y-P, significantly increased the expression of p-PI3K and p-Akt, but reduced p-NF-κB expression. It also inhibited M1 polarization of microglia, reduced neuroinflammation, and improved hippocampal neurogenesis and cognitive function in neonatal rats with HIBD. Our findings illustrate that activation of the CD200/CD200R1 axis inhibits the NF-κB-mediated M1 polarization of microglia to improve HIBD-induced cognitive impairment and hippocampal neurogenesis disorder via the PI3K/Akt signaling pathway.

Integrating TSPO PET imaging and transcriptomics to unveil the role of neuroinflammation and amyloid-β deposition in Alzheimer's disease

PURPOSE

Despite the revealed role of immunological dysfunctions in the development and progression of Alzheimer's disease (AD) through animal and postmortem investigations, direct evidence regarding the impact of genetic factors on microglia response and amyloid-β (Aβ) deposition in AD individuals is lacking. This study aims to elucidate this mechanism by integrating transcriptomics and TSPO, Aβ PET imaging in clinical AD cohort.

METHODS

We analyzed 85 patients with PET/MR imaging for microglial activation (TSPO, [18F]DPA-714) and Aβ ([18F]AV-45) within the prospective Alzheimer's Disease Immunization and Microbiota Initiative Study Cohort (ADIMIC). Immune-related differentially expressed genes (IREDGs), identified based on AlzData, were screened and verified using blood samples from ADIMIC. Correlation and mediation analyses were applied to investigate the relationships between immune-related genes expression, TSPO and Aβ PET imaging.

RESULTS

TSPO uptake increased significantly both in aMCI (P < 0.05) and AD participants (P < 0.01) and showed a positive correlation with Aβ deposition (r = 0.42, P < 0.001). Decreased expression of TGFBR3, FABP3, CXCR4 and CD200 was observed in AD group. CD200 expression was significantly negatively associated with TSPO PET uptake (r =-0.33, P = 0.013). Mediation analysis indicated that CD200 acted as a significant mediator between TSPO uptake and Aβ deposition (total effect B = 1.92, P = 0.004) and MMSE score (total effect B =-54.01, P = 0.003).

CONCLUSION

By integrating transcriptomics and TSPO PET imaging in the same clinical AD cohort, this study revealed CD200 played an important role in regulating neuroinflammation, Aβ deposition and cognitive dysfunction.

CD200/CD200R: Bidirectional Role in Cancer Progression and Immunotherapy

As an immune checkpoint molecule, CD200 serves a foundational role in regulating immune homeostasis and promoting self-tolerance. While CD200 expression occurs in various immune cell subsets and normal tissues, its aberrant expression patterns in hematologic malignancies and solid tumors have been linked to immune evasion and cancer progression under pathological conditions, particularly through interactions with its cognate receptor, CD200R. Through this CD200/CD200R signaling pathway, CD200 exerts its immunosuppressive effects by inhibiting natural killer (NK) cell activation, cytotoxic T cell functions, and M1-polarized macrophage activity, while also facilitating expansion of myeloid-derived suppressor cells (MDSCs) and Tregs. Moreover, CD200/CD200R expression has been linked to epithelial-to-mesenchymal transition and distant metastasis, further illustrating its role in cancer progression. Conversely, CD200 has also been shown to exert anti-tumor effects in certain cancer types, such as breast carcinoma and melanoma, indicating that CD200 may exert bidirectional effects on cancer progression depending on the specific tumor microenvironment (TME). Regardless, modulating the CD200/CD200R axis has garnered clinical interest as a potential immunotherapeutic strategy for cancer therapy, as demonstrated by early-phase clinical trials. However, further research is necessary to fully understand the complex interactions of CD200 in the tumor microenvironment and to optimize its therapeutic potential in cancer immunotherapy.

Activation of the CD200/CD200R1 axis attenuates neuroinflammation and improves postoperative cognitive dysfunction via the PI3K/Akt/NF-κB signaling pathway in aged mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a neurological complication occurring after anesthesia and surgery. Neuroinflammation plays a critical role in the pathogenesis of POCD, and the activation of the cluster of differentiation 200 (CD200)/CD200R1 axis improves neurological recovery in various neurological disorders by modulating inflammation. The aim of this study was to investigate the impact and underlying mechanism of CD200/CD200R1 axis on POCD in aged mice.

METHODS

The model of POCD was established in aged mice. To assess the learning and memory abilities of model mice, the Morris water maze test was implemented. CD200Fc (CD200 fusion protein), CD200R1 Ab (anti-CD200R1 antibody), and 740Y-P (a specific PI3K activator) were used to evaluate the effects of the CD200/CD200R1/PI3K/Akt/NF-κB signaling pathway on hippocampal microglial polarization, neuroinflammation, synaptic activity, and cognition in mice.

RESULTS

It was observed that anesthesia/surgery induced cognitive decline in aged mice, increased the levels of tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1 β and decreased the levels of postsynaptic density protein 95 (PSD-95), synaptophysin (SYN) in the hippocampus. Moreover, CD200Fc and 740Y-P attenuated neuroinflammation and synaptic deficits and reversed cognitive impairment via the phosphatidylinositol 3-kinase (PI3K)/ protein kinase B (Akt)/nuclear factor-kappa B (NF-κB) signaling pathway, whereas CD200R1 Ab administration exerted the opposite effects. Our results further show that the CD200/CD200R1 axis modulates M1/M2 polarization in hippocampal microglia via the PI3K/Akt/NF-κB signaling pathway.

CONCLUSIONS

Our findings indicate that the activation of the CD200/CD200R1 axis reduces neuroinflammation, synaptic deficits, and cognitive impairment in the hippocampus of aged mice by regulating microglial M1/M2 polarization via the PI3K/Akt/NF-κB signaling pathway.

PPAR-γ promotes the polarization of rat retinal microglia to M2 phenotype by regulating the expression of CD200-CD200R1 under hypoxia

BACKGROUND

Recent reports suggest that peroxisome proliferator-activated receptor-γ (PPAR-γ) could promote microglial M2 polarization to inhibit inflammation. However, the specific molecular mechanisms that trigger PPAR-γ's anti-inflammatory ability in microglia are yet to be expounded. Thus, in this study, we aimed to explore the molecular mechanisms behind the anti-inflammatory effects of PPAR-γ in hypoxia-stimulated rat retinal microglial cells.

METHODS AND RESULTS

We used shRNA expressing lentivirus to knock down PPAR-γ and CD200 genes, and we assessed hypoxia-induced polarization markers release - M1 (iNOS, IL-1β, IL-6, and TNF-α) and M2 (Arg-1, YM1, IL-4, and IL-10) by RT-PCR. We also monitored PPAR-γ-related signals (PPAR-γ, PPAR-γ in cytoplasm or nucleus, CD200, and CD200Rs) by Western blot and RT-PCR. Our results showed that hypoxia enhanced PPAR-γ and CD200 expressions in microglial cells. Moreover, PPAR-γ agonist 15d-PGJ2 elevated CD200 and CD200R1 expressions, whereas sh-PPAR-γ had the opposite effect. Following hypoxia, expressions of M1 markers increased significantly, while those of M2 markers decreased, and the above effects were attenuated by 15d-PGJ2. Conversely, knocking down PPAR-γ or CD200 inhibited the polarization of microglial cells to M2 phenotype.

CONCLUSION

Our findings demonstrated that PPAR-γ performed an anti-inflammatory function in hypoxia-stimulated microglial cells by promoting their polarization to M2 phenotype via the CD200-CD200R1 pathway.

Decreased expression of CD200 on peripheral blood leukocytes in alcohol dependence

Chronic alcohol use induces innate immune genes, which activate the innate immune system. Neuroimmune regulatory proteins [e.g., Cluster of Differentiation 200 (CD200)] are immune response regulators and are involved in balancing the immune response. This study aimed to investigate the expression of CD200 on the surface of peripheral blood leukocytes in patients with alcohol use disorder and compare them with controls. Fifty male patients with alcohol use disorder were included in the study. A baseline assessment was done, and alcohol use history, craving, and withdrawal scores were collected. A 2-mL venous blood sample was collected from cases and controls for immunophenotyping of CD200. The control group consisted of 50 participants with similar socio-economic backgrounds. The cellular expression of CD200 on total leukocytes (median ± IQR) [39.94 (28.85, 50.01)] in cases was significantly lower compared to controls [45.07 (37.70, 51.69)] (U = 896, p = 0.015). Expression of CD200 on lymphocytes in cases was negatively correlated with years of heavy drinking and this was statistically significant (r = -0.321, p = 0.023). The study indicates that cellular expression of CD200 on the surface of peripheral blood leukocytes is reduced in alcohol-dependent patients. This reduction can contribute to exaggerated immune activity, release of pro-inflammatory cytokines, chronic microglial activation, neuroinflammation, and neurodegeneration in alcohol dependence.

Adjuvantation of whole-killed Leishmania vaccine with anti-CD200 and anti-CD300a antibodies potentiates its efficacy and provides protection against wild-type parasites

One of the major reasons behind the limited success of vaccine candidates against all forms of leishmaniasis is the inability of parasitic antigens to induce robust cell-mediated immunity and immunological memory. Here we find, for the first time, that the adjuvantation of whole-killed Leishmania vaccine (Leishvacc) with anti-CD200 and anti-CD300a antibodies enhances CD4+ T cells mediated immunity in vaccinated mice and provides protection against wild-type parasites. The antibody adjuvantation, either alone or with a TLR4 agonist monophosphoryl A (MPL-A), induced the production of pro-inflammatory cytokines viz., IFN-γ, TNF-α, and IL-2 by antigen experienced CD4+ T cells, and also enhanced their rate of conversion into their memory phenotypes against Leishvacc antigens. The antibody adjuvanted vaccine also promoted the generation of IgG2a-mediated protective humoral immunity in vaccinated mice. Further, the mice vaccinated with antibodies adjuvanted vaccine showed strong resilience against metacyclic forms of L. donovani parasites as we observed reduced clinical features such as splenomegaly, hepatomegaly, granulomatous tissues in the liver, and parasitic load in their spleen. The findings of this study demonstrate that the anti-CD200 and anti-CD300a antibodies have potential to increase the protective efficacy of the whole-killed Leishmania vaccine, and opens up a new gateway to diversify the roles of immune checkpoints in vaccine development against leishmaniasis.

Immune Checkpoint Pathway Expression in Lymphocyte Subpopulations in Patients with Common Variable Immunodeficiency and Chronic Lymphocytic Leukemia

This study aims to gain a deeper understanding of chronic lymphocytic leukemia (CLL) and common variable immunodeficiency (CVID) by studying immune cells and specific immune checkpoint signaling pathways. The analysis of the percentage of selected immune points and their ligands (PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200) on peripheral blood lymphocyte subpopulations was performed using flow cytometry, and additional analyses determining the serum concentration of the above-mentioned molecules were performed using enzyme immunoassay tests. The obtained results indicate several significant changes in the percentage of almost all tested molecules on selected subpopulations of T and B lymphocytes in both CVID and CLL patients in relation to healthy volunteers and between the disease subunits themselves. The results obtained were also supported by the analysis of the serum concentration of soluble molecules tested. By uncovering valuable insights, we hope to enhance our comprehension and management of these conditions, considering both immunodeficiencies and hematological malignancies. Understanding the role of these signaling pathways in disease development and progression may lead to the development of modern, personalized diagnostic and therapeutic strategies. Ultimately, this knowledge may enable the monitoring of the immune system in patients with CVID and CLL, paving the way for improved patient care in the future.

Exploring the Significance of Immune Checkpoints and EBV Reactivation in Antibody Deficiencies with Near-Normal Immunoglobulin Levels or Hyperimmunoglobulinemia

This study delves into the intricate landscape of primary immunodeficiencies, with a particular focus on antibody deficiencies characterized by near-normal immunoglobulin levels or hyperimmunoglobulinemia. Contrary to the conventional focus on genetic dysregulation, these studies investigate the key roles of immune checkpoints, such as PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200, on selected subpopulations of T and B lymphocytes and their serum concentrations of soluble forms in patients recruited for the studies in healthy volunteers. In addition, the studies also show the role of Epstein-Barr virus (EBV) reactivation and interactions with tested pathways of immune checkpoints involved in the immunopathogenesis of this disease. By examining the context of antibody deficiencies, this study sheds light on the nuanced interplay of factors beyond genetics, particularly the immune dysregulations that occur in the course of this type of disease and the potential role of EBV reactivation, which affects the clinical presentation of patients and may contribute to the development of cancer in the future, especially related to hematological malignancies.

Emerging Immune Checkpoint Molecules on Cancer Cells: CD24 and CD200

Cancer immunotherapy strategies are based on the utilization of immune checkpoint inhibitors to instigate an antitumor immune response. The efficacy of immune checkpoint blockade, directed at adaptive immune checkpoints, has been demonstrated in select cancer types. However, only a limited subset of patients has exhibited definitive outcomes characterized by a sustained response after discontinuation of therapy. Recent investigations have highlighted the significance of immune checkpoint molecules that are overexpressed in cancer cells and inhibit myeloid lineage immune cells within a tumor microenvironment. These checkpoints are identified as potential targets for anticancer immune responses. Notably, the immune checkpoint molecules CD24 and CD200 have garnered attention owing to their involvement in tumor immune evasion. CD24 and CD200 are overexpressed across diverse cancer types and serve as signaling checkpoints by engaging their respective receptors, Siglec-10 and CD200 receptor, which are expressed on tumor-associated myeloid cells. In this review, we summarized and discussed the latest advancements and insights into CD24 and CD200 as emergent immune checkpoint moieties, further delving into their therapeutic potentials for cancer treatment.

Evaluation of Diagnostic Usefulness of CD200 Expression in B-cell Chronic Lymphoproliferative Disorders

Immunophenotyping by flow cytometry (FCM) is a useful diagnostic tool for the evaluation of mature B-cell neoplasms (MBN). Here, CD200 expression may play a significant role and improve the distinction between various MBNs, but any potential as a prognostic marker is yet to be established. The present prospective study was conducted on all the suspected cases of MBNs. Immunophenotyping was done using a BD FACS Canto FCM using a panel of 4 to 6 color combinations of monoclonal antibodies; CD45, CD34, CD5, CD19, CD20, CD22, CD23, CD79b, FMC7, CD10, CD38, ZAP70, CD200, IgG, IgM, CD25, CD103, CD2, CD3, CD11c as well as κ and λ light chains. CD200 expression was compared in different subgroups. Of the total of 130 cases included in the study, CD200 was positive in 118 cases (90%). CD200 was expressed in 100% of the cases of CLL(86 cases), atypical CLL(06 cases), HCL(14 cases), FL(02 cases), SMZL(04 cases), LPL (01 case), and low-grade NHL (05 cases), with the highest intensity of fluorescence in HCL followed by CLL. All the cases of MCL and PLL were exclusively negative for CD200. In conclusion, the results of the present study support inclusion of this marker in the flow cytometric panels for the differential diagnosis of MBNs.

Could Immune Checkpoint Disorders and EBV Reactivation Be Connected in the Development of Hematological Malignancies in Immunodeficient Patients?

Primary immunodeficiencies (PIDs) and secondary immunodeficiencies (SIDs) are characterized by compromised immune function, rendering individuals susceptible to infections and potentially influencing cancer development. Epstein-Barr virus (EBV), a widespread herpesvirus, has been linked to cancer, particularly in those with weakened immune systems. This study aims to compare selected immune parameters, focusing on immune checkpoint molecules (PD-1/PD-L1, CTLA-4/CD86, CD200R/CD200), and EBV reactivation in patients with chronic lymphocytic leukemia (CLL, a representative of SIDs) and common variable immunodeficiency (CVID, a representative of PIDs). We performed a correlation analysis involving patients diagnosed with CLL, CVID, and a healthy control group. EBV reactivation was assessed using specific antibody serology and viral load quantification. Peripheral blood morphology, biochemistry, and immunophenotyping were performed, with emphasis on T and B lymphocytes expressing immune checkpoints and their serum concentrations. Our findings revealed elevated EBV reactivation markers in both CLL and CVID patients compared with healthy controls, indicating increased viral activity in immunodeficient individuals. Furthermore, immune checkpoint expression analysis demonstrated significantly altered percentages of T and B lymphocytes expressing PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200 in CLL and CVID patients. This suggests a potential interplay between immune checkpoint dysregulation and EBV reactivation in the context of immunodeficiency. In conclusion, our study underscores the intricate relationship between immune dysfunction, EBV reactivation, and immune checkpoint modulation in the context of immunodeficiency-associated cancers. The altered expression of immune checkpoints, along with heightened EBV reactivation, suggests a potential mechanism for immune evasion and tumor progression. These findings provide insights into the complex interactions that contribute to cancer development in immunocompromised individuals, shedding light on potential therapeutic targets for improved management and treatment outcomes. Further investigations are warranted to elucidate the underlying mechanisms and to explore potential interventions to mitigate cancer risk in these patient populations.

Diagnostic Utility of CD200 Immunohistochemistry in Distinguishing EBV-Positive Large B-Cell Lymphoma From Classic Hodgkin Lymphoma

OBJECTIVES

Epstein-Barr virus-positive large B-cell lymphoma (EBV+ LBCL) is a heterogeneous group of diseases that may resemble classic Hodgkin lymphoma (CHL) both morphologically and immunophenotypically. However, these diseases are treated with different therapies and carry distinct prognoses. We examined CD200 expression by immunohistochemistry in EBV+ LBCL and evaluated its diagnostic utility in the differential diagnosis with CHL.

METHODS

CD200 immunohistochemistry was performed on archival material from 20 cases of CHL (11 EBV+, 9 EBV-), 11 cases of EBV+ LBCL, and 10 cases of diffuse large B-cell lymphoma, not otherwise specified (DLBCL NOS). Staining pattern and intensity (0-3+ scale) were recorded.

RESULTS

CD200 positivity was seen in Reed-Sternberg cells in 19 (95%) of 20 cases of CHL, predominantly in a strong (3+, 15/19) and diffuse (>50% of cells, 17/19) pattern. In contrast, CD200 was negative in 8 (73%) of 11 cases of EBV+ LBCL; the 3 positive cases showed 1 to 2+ staining in less than 50% of lesional cells. All cases of DLBCL NOS were negative for CD200.

CONCLUSIONS

CD200 may be a useful immunophenotypic marker in differentiating EBV+ LBCL from CHL, with negative to partial/weak staining favoring a diagnosis of EBV+ LBCL and strong diffuse staining favoring a diagnosis of CHL.

Twenty-four-color full spectrum flow cytometry panel for minimal residual disease detection in acute myeloid leukemia

Full spectrum flow cytometry brings a breakthrough for minimal residual disease (MRD) detection in acute myeloid leukemia (AML). We aimed to explore the role of a new panel in MRD detection. We established a 24-color full-spectrum flow cytometry panel. A tube of 24-color antibodies included CD45, CD117, CD34, HLA-DR, CD15, CD64, CD14, CD11c, CD11b, CD13, CD33, CD371, CD7, CD56, CD19, CD4, CD2, CD123, CD200, CD38, CD96, CD71, CD36, and CD9. We discovered that when a tube meets 26 parameters (24 colors), these markers were not only limited to the observation of MRD in AML, but also could be used for fine clustering of bone marrow cells. Mast cells, basophils, myeloid dendritic cells, and plasmacoid dendritic cells were more clearly observed. In addition, immune checkpoint CD96 had the higher expression in CD117+ myeloid naive cells and CD56dimNK cells, while had the lower expression in CD56briNK cells in AML-MRD samples than in normal bone marrow samples. CD200 expression was remarkably enhanced in CD117+ myeloid naive cells, CD4+ T cells, T cells, activated T cells, CD56dimNK cells, and CD56briNK cells in AML-MRD samples. Our results can be used as important basis for auxiliary diagnosis, prognosis judgment, treatment guidance, and immune regulation in AML.

CD200Fc limits dendritic cell and B-cell activation during chronic allergen exposures

Allergic asthma is a chronic inflammatory disease characterized by Th2, conventional dendritic cell, and B-cell activation. In addition to excessive inflammation, asthma pathogenesis includes dysregulation of anti-inflammatory pathways, such as the CD200/CD200R pathway. Thus, we investigated whether a CD200R agonist, CD200Fc, could disrupt the inflammatory cascade in chronic allergic asthma pathogenesis using a mice model of experimental asthma. Mice were exposed to house dust mites for 5 wk, and CD200Fc treatment was initiated after chronic inflammation was established (starting on week 4). We demonstrate that chronic house dust mite exposure altered CD200 and CD200R expression on lung immune cell populations, including upregulation of CD200 on alveolar macrophages and reduced expression of CD200 on conventional dendritic cells. CD200Fc treatment does not change bronchoalveolar cellular infiltration, but it attenuates B-cell activation and skews the circulating immunoglobulin profile toward IgG2a. This is accompanied by reduced activation of conventional dendritic cells, including lower expression of CD40, especially on conventional dendritic cell subset 2 CD200R+. Furthermore, we confirm that CD200Fc can directly modulate conventional dendritic cell activation in vitro using bone marrow-derived dendritic cells. Thus, the CD200/CD200R pathway is dysregulated during chronic asthma pathogenesis, and the CD200R agonist modulates B-cell and dendritic cell activation but, in our chronic model, is not sufficient to alter inflammation measured in bronchoalveolar lavage.

CD200 in dentate gyrus improves depressive-like behaviors of mice through enhancing hippocampal neurogenesis via alleviation of microglia hyperactivation

BACKGROUND

Neuroinflammation and microglia play critical roles in the development of depression. Cluster of differentiation 200 (CD200) is an anti-inflammatory glycoprotein that is mainly expressed in neurons, and its receptor CD200R1 is primarily in microglia. Although the CD200-CD200R1 pathway is necessary for microglial activation, its role in the pathophysiology of depression remains unknown.

METHODS

The chronic social defeat stress (CSDS) with behavioral tests were performed to investigate the effect of CD200 on the depressive-like behaviors. Viral vectors were used to overexpress or knockdown of CD200. The levels of CD200 and inflammatory cytokines were tested with molecular biological techniques. The status of microglia, the expression of BDNF and neurogenesis were detected with immunofluorescence imaging.

RESULTS

We found that the expression of CD200 was decreased in the dentate gyrus (DG) region of mice experienced CSDS. Overexpression of CD200 alleviated the depressive-like behaviors of stressed mice and inhibition of CD200 facilitated the susceptibility to stress. When CD200R1 receptors on microglia were knocked down, CD200 was unable to exert its role in alleviating depressive-like behavior. Microglia in the DG brain region were morphologically activated after exposure to CSDS. In contrast, exogenous administration of CD200 inhibited microglia hyperactivation, alleviated neuroinflammatory response in hippocampus, and increased the expression of BDNF, which in turn ameliorated adult hippocampal neurogenesis impairment in the DG induced by CSDS.

CONCLUSIONS

Taken together, these results suggest that CD200-mediated alleviation of microglia hyperactivation contributes to the antidepressant effect of neurogenesis in dentate gyrus in mice.

23ME-00610, a genetically informed, first-in-class antibody targeting CD200R1 to enhance antitumor T cell function

Immune checkpoint inhibition (ICI) has revolutionized cancer treatment; however, only a subset of patients benefit long term. Therefore, methods for identification of novel checkpoint targets and development of therapeutic interventions against them remain a critical challenge. Analysis of human genetics has the potential to inform more successful drug target discovery. We used genome-wide association studies of the 23andMe genetic and health survey database to identify an immuno-oncology signature in which genetic variants are associated with opposing effects on risk for cancer and immune diseases. This signature identified multiple pathway genes mapping to the immune checkpoint comprising CD200, its receptor CD200R1, and the downstream adapter protein DOK2. We confirmed that CD200R1 is elevated on tumor-infiltrating immune cells isolated from cancer patients compared to the matching peripheral blood mononuclear cells. We developed a humanized, effectorless IgG1 antibody (23ME-00610) that bound human CD200R1 with high affinity (KD <0.1 nM), blocked CD200 binding, and inhibited recruitment of DOK2. 23ME-00610 induced T-cell cytokine production and enhanced T cell-mediated tumor cell killing in vitro. Blockade of the CD200:CD200R1 immune checkpoint inhibited tumor growth and engaged immune activation pathways in an S91 tumor cell model of melanoma in mice.

PD1hi CD200hi CD4+ exhausted T cell increase immunotherapy resistance and tumour progression by promoting epithelial-mesenchymal transition in bladder cancer

BACKGROUND

Bladder cancer (BLCA) is one of the most diagnosed cancers in humans worldwide. Recently, immunotherapy has become a main treatment option for BC. However, most BLCA patients do not respond to immune checkpoint inhibitors or relapse after immunotherapy. Therefore, it is very important to identify novel biomarkers for the prediction of immunotherapy response in B patients.

METHODS

Pancancer single-cell RNA sequencing (scRNA-seq) data were used to identify the clusters of CD4⁺ T cells in the tumour microenvironment (TME). The clinical significance of key CD4⁺ T-cell clusters was evaluated based on the survival data of two independent immunotherapy bladder cancer (BLCA) cohorts. We also investigated the function of key clusters of CD4⁺ T cell in the TME of BC cells in vitro.

RESULTS

This study identified two novel exhausted CD4⁺ T-cell subpopulations with the expression of PD1^hi CD200^hi or PD1^hi CD200^low in BC patients. Moreover, BLCA patients with a high level of PD1^hi CD200^hi CD4⁺ exhausted T cell showed immunotherapy resistance. Cell function analysis demonstrated that PD1^hi CD200^hi CD4⁺ exhausted T cell can promote epithelial-mesenchymal transition (EMT) and angiogenesis in BLCA cells. In addition, PD1^hi CD200^hi CD4⁺ exhausted T cells were shown to communicate with malignant BLCA cells through the GAS6-AXL axis. Finally, we also found that GAS6 expression is upregulated in B cells by METTL3-mediated m6A modification.

CONCLUSIONS

PD1^hi CD200^hi CD4⁺ exhausted T cell may serve as a novel biomarker for poor prognosis and immunotherapy resistance in B. Targeted inhibitors of PD1^hi CD200^hi CD4⁺ exhausted T cells may help improve the efficacy of immunotherapy.

Cancel cancer: The immunotherapeutic potential of CD200/CD200R blockade

Immune checkpoint molecules function to inhibit and regulate immune response pathways to prevent hyperactive immune activity from damaging healthy tissues. In cancer patients, targeting these key molecules may serve as a valuable therapeutic mechanism to bolster immune function and restore the body's natural defenses against tumors. CD200, an immune checkpoint molecule, is a surface glycoprotein that is widely but not ubiquitously expressed throughout the body. By interacting with its inhibitory receptor CD200R, CD200 suppresses immune cell activity within the tumor microenvironment, creating conditions that foster tumor growth. Targeting the CD200/CD200R pathway, either through the use of monoclonal antibodies or peptide inhibitors, has shown to be effective in boosting anti-tumor immune activity. This review will explore CD200 and the protein's expression and role within the tumor microenvironment, blood endothelial cells, and lymph nodes. This paper will also discuss the advantages and challenges of current strategies used to target CD200 and briefly summarize relevant preclinical/clinical studies investigating the immunotherapeutic efficacy of CD200/CD200R blockade.

Prognostic Role of CD200 in Acute Lymphoblastic Leukemia Patients

BACKGROUND

Overexpression of CD200 in ALL patients indicates that it may be useful in the characterization of leukemia initiating cells (LIC). We aim at investigating the expression pattern of CD200 on leukemic B cells and the correlation of CD200 expression with various clinical and laboratory findings in 62 newly diagnosed acute lymphoblastic leukemia patients.

METHODS

All patients were subjected to full history taking, a thorough clinical examination, and laboratory investigations, which included complete blood count (CBC), BM aspiration, immunophenotyping of blast cells, and CD200 expression.

RESULTS

There is a higher statistically significant mean value of CD200 expression among the cases (66.15 ± 23.08) than the control group (0.37 ± 0.2) (p value ≤ 0.001). CD200 expression shows a significant correlation with total leucocytic count and hemoglobin level (p = 0.001, 0.03, respectively).

CONCLUSIONS

This study showed that CD200 expression was expressed in 100% of the patients. Correlations between CD200 expression and different laboratory data of patients revealed that there was an impact of CD200 on different diagnostic findings. After the follow-up of the patients, we found that the use of PRISM function of the software could add value to the detection of minimal residual disease.

Immunological Parameters in Patients Suffering from Atopic Dermatitis and Either Treated or Non-Treated with Dupilumab

OBJECTIVE

The aim of the study is to analyze the absolute count of leukocytes, neutrophils, monocytes, eosinophils, T cells, natural killer cells, B cells and to evaluate the expression of functionally important CD23 and CD200 molecules on B cells in patients suffering from atopic dermatitis (AD), (with and without dupilumab therapy).

MATERIALS AND METHODS

We examined 45 patients suffering from AD - 32 patients without dupilumab treatment (10 men, 22 women, average age 35.0 years), 13 patients with dupilumab treatment (7 men, 6 women, average age 43.4 years) and 30 healthy control (10 men, 20 women, average age 44.7 years). Immunophenotype was examined by flow cytometry (Navios Flow Cytometer - Beckman Coulter). The blood count was examined with a Sysmex XN 3000, Sysmex SP10, microscope DI60 for digital morphology evaluating cell division and microscope Olympus BX40. We compared the absolute count of leukocytes and their subsets, T cells (CD4, CD8), natural killers cells, absolute and relative count of B lymphocytes and expression of surface molecules CD23 and CD200 on B cells in AD patients and in control group. Non-parametric Kruskal-Wallis one-factor analysis of variance with post-hoc (follow-up multiple comparison) and Dunn's test with Bonferroni modification of significance level were used for statistical analysis.

RESULTS

We confirmed the significantly higher number of neutrophils, monocytes and eosinophils and higher expression of CD23 and CD200 on B cells in peripheral blood of AD patients (either with or without dupilumab) therapy. We demonstrated the lower number of CD8+ T cells.

CONCLUSION

We demonstrated the difference in the count of white blood cells populations in patients suffering from AD compared with healthy control. There were a differences in the expression of immunoregulatory molecules CD23 and CD200 on B cells in AD patients (either with or without dupilumab therapy) in comparison to healthy controls.

Circulating CD200 is increased in the secretory phase of women with endometriosis as is endometrial mRNA, and endometrial stromal cell CD200R1 is increased in spite of reduced mRNA

PROBLEM

Estrogen-dependent extrauterine implantation and growth of menstrual endometrial tissue affects roughly 10% of reproductive age women and depends on suppression of local innate immune defenses to prevent ectopic tissue rejection. Immunohistochemistry has shown the immune check-point inhibitor CD200 which can suppress rejection is expressed in eutopic endometrium and in ectopic deposits. Soluble CD200 accumulated in venules draining eutopic and ectopic endometrium of endometriosis cases in the secretory phase but not proliferative phase of the menstrual cycle, and should be increased in the circulation.

METHOD OF STUDY

Sera from endometriosis and non-endometriosis controls were tested by ELISA for CD200. Endometrial CD200, CD200R1 and CD200R2 mRNA in eutopic was quantified by RT-PCR and localized by in situ hybridization. CD200R1 protein was quantified by immunohistochemistry.

RESULTS

Secretory phase serum CD200 was elevated in women with endometriosis compared to controls. Serum CD200 correlated with matched endometrial CD200 mRNA levels. Expression of mRNA for CD200R1 which signals immune suppression was decreased whereas mRNA for the CD200R2 activating receptor was increased. In situ staining of CD200R1 and CD200R2 mRNA showed both receptors were expressed and the fraction of CD200R that is CD200R1 was reduced in secretory and menstrual phase endometriosis endometrium consistent with the RT-PCR result. By contrast, CD200R1 protein and CD200R1 fraction of total CD200R protein were increased in endometriosis.

CONCLUSIONS

Failure to suppress circulating CD200 levels in the secretory phase had an 87% specificity and 90% sensitivity for endometriosis. CD200 and increased CD200R1 expression may facilitate development of ectopic deposits by suppressing rejection mechanisms.

Significance of placental CD200 expression in patients with preeclampsia: Comparison between early‑ and late‑onset patients

Preeclampsia, characterized by high blood pressure and proteinuria during pregnancy, causes serious complications in both the mother and the fetus. Although there have been several studies on the causes of preeclampsia, the detailed mechanism of this disease remains unclear. Moreover, a few reports have focused on the causes of preeclampsia in number of weeks at onset. The present study aimed to elucidate the differences between early‑ and late‑onset preeclampsia. This study enrolled patients with preeclampsia from January 2014 to December 2020. They were classified into early‑ (<34 weeks) and late‑onset (≥34 weeks) preeclampsia groups. The expression profiles of 770 immune‑related genes were studied in the placental tissue from five patients each in the early‑ and late‑onset groups. The expression of CD200 in the trophoblasts of the placenta of 26 and 27 patients in early‑ and late‑onset groups, respectively, was also analyzed using immunostaining. Analysis of extracted RNA indicated that CD200 was significantly upregulated in the early‑onset group compared with late‑onset group and normal control. Immunostaining for CD200 demonstrated a significantly increased expression in the early‑onset group compared with the late‑onset group. The present study demonstrated that upregulation of CD200, which belongs to the immunoglobulin superfamily and is recognized as a molecule that acts in immune tolerance via inhibition of classical macrophage activation, may be associated with early‑onset preeclampsia, although it remains unknown whether upregulation of CD200 expression is a cause or effect of the development of early‑onset preeclampsia. Early‑onset preeclampsia might have a different mechanism from that of late‑onset; thus, further studies are needed to clarify the mechanism of these conditions for adequate treatment.

Application of modified Matutes score containing CD200 in diagnosis of chronic lymphocytic leukemia

OBJECTIVES

Immunophenotyping technique is a powerful tool for the diagnosis and differential diagnosis of chronic lymphocytic leukemia (CLL) and other B-cell chronic lymphoproliferative diseases (B-CLPD). CD200 is strongly expressed in CLL. This study aims to analyze the clinical value of modified Matutes score (MMS) containing CD200 in the diagnosis of CLL.

METHODS

We retrospectively analyzed 103 B-CLPD patients diagnosed from January 2020 to July 2021, including 64 CLL patients, 11 follicular lymphoma (FL) patients, 14 mantle cell lymphoma (MCL) patients, 6 marginal zone lymphoma (MZL) patients, 1 hairy cell leukemia (HCL) patient, and 7 lymphoplasmic lymphoma/Waldenstrom macroglobulinemia (LPL/WM) patients. The expression of CD markers between the CLL group and the non-CLL group was compared, and the sensitivity, specificity, and clinical consistency of MMS and Royal Marsden Hospital (RMH) immunophenotyping score system were analyzed.

RESULTS

There were significant differences in the expressions of CD5, CD23, FMC7, CD22, CD79b, CD200, and sIg between the CLL group and the non-CLL group (χ2 values were 37.42, 54.98, 30.71, 11.67, 55.26, 68.48, and 17.88, respectively, all P<0.01). When the RMH immunophenotyping score≥4, the sensitivity was 79.7%, and the specificity was 100%. When the MMS≥3, the sensitivity was 95.3%, and the specificity was 100%. The Kappa coefficient of RMH immunophenotyping system was 0.677, and the Kappa coefficient of MMS system was 0.860.

CONCLUSIONS

The MMS system containing CD200 has better sensitivity and same specificity compared with RMH immunophenotyping system, and MMS system may be more useful in the diagnosis of CLL.

CD200 as a Potential New Player in Inflammation during Rotator Cuff Tendon Injury/Repair: An In Vitro Model

Rotator cuff tendon (RCT) disease results from multifactorial mechanisms, in which inflammation plays a key role. Pro-inflammatory cytokines and tendon stem cell/progenitor cells (TSPCs) have been shown to participate in the inflammatory response. However, the underlying molecular mechanism is still not clear. In this study, flow cytometry analyses of different subpopulations of RCT-derived TSPCs demonstrate that after three days of administration, TNFα alone or in combination with IFNγ significantly decreases the percentage of CD146+CD49d+ and CD146+CD49f+ but not CD146+CD109+ TSPCs populations. In parallel, the same pro-inflammatory cytokines upregulate the expression of CD200 in the CD146+ TSPCs population. Additionally, the TNFα/IFNγ combination modulates the protein expression of STAT1, STAT3, and MMP9, but not fibromodulin. At the gene level, IRF1, CAAT (CAAT/EBPbeta), and DOK2 but not NF-κb, TGRF2 (TGFBR2), and RAS-GAP are modulated. In conclusion, although our study has several important limitations, the results highlight a new potential role of CD200 in regulating inflammation during tendon injuries. In addition, the genes analyzed here might be new potential players in the inflammatory response of TSPCs.

Autophagy inhibition restores CD200 expression under IL-1β microenvironment in placental mesenchymal stem cells of fetal origin and improves its pulmonary fibrosis therapeutic potential

BACKGROUND

Mesenchymal stem cells (MSCs) are promising remedies for various inflammatory disease including pulmonary fibrosis (PF). However, the properties of MSCs in PF pathological microenvironment remain unclear. In this study, the efficacy of autophagy in placental mesenchymal stem cells of fetal origin (fPMSCs) in either IL-1β treatment or BLM induced pulmonary fibrosis mice model was examined.

METHODS

The characteristic of fPMSCs was identified by morphological observation, flow cytometry and differentiation potential. In vitro experiments, fPMSCs were stimulated with IL-1β, to mimic inflammatory microenvironment of pulmonary fibrosis. The immunosuppressive properties and autophagic function in fPMSCs treated with IL-1β were evaluated by both macrophage cells THP-1 activation and the expression of CD200 situation, autophagy marker and MAPK signaling pathway. The in vivo anti-fibrotic activity of fPMSCs interfering autophagy was evaluated by using BLM induced pulmonary fibrosis mice model.

RESULTS

fPMSCs belonged to CD73⁺CD90⁺CD105⁺/CD14^- CD34^-CD45^-HLA-DR^- cells, and capable differentiation to adipogenic, osteogenic and chondrogenic cells. In addition, immunoinhibitory activity of fPMSCs for macrophage was restrained by IL-1β treatment in CD200 dependent manner. Suppression of autophagy by sh-Atg5 lentivirus increased the expression of CD200 and ratio of CD200 positive fPMSCs, and enhanced fPMSCs immunosuppression for THP-1 activation. Mechanistically, IL-1β induced autophagy regulated by p38 signaling cascade. In vivo, autophagy inhibition induced by Atg5 knockdown in fPMSCs resulted in strengthening antifibrotic effects on PF mice model.

CONCLUSIONS

Collectively, autophagy derived from inflammatory microenvironment hampered the immunoinhibitory properties of MSCs. Based on this, adjustment of autophagy may be a valid approach to facilitate their immunomodulatory and anti-fibrotic efficacy.

CD200 expression on Sezary cells: A valuable tool for flow cytometric assessment of peripheral blood T-cell neoplasms

BACKGROUND

CD200 (OX-2) is a valuable marker in the diagnosis of B-cell neoplasms and is commonly used in the screening panels for assessment of peripheral blood B-cell lymphoproliferative disorders. However, there is limited understanding about CD200 expression in T-cell neoplasms. A previous study has shown that CD200 is expressed on the neoplastic cells of angioimmunoblastic T-cell lymphoma (AITL) by immunohistochemistry, but no study has evaluated CD200 expression in T-cell neoplasms by flow cytometry.

METHODS

We assessed CD200 expression in peripheral blood T-cell lymphoproliferative disorders by retrospective analysis of our institutional flow cytometry screening database over a 6-year period.

RESULTS

In addition to AITL, we identified CD200 expression in a significant number of mycosis fungoides/Sezary syndrome cases (58%, 19 of 33 samples), while most other T-cell neoplasms were negative for CD200. These findings were confirmed by CD200 immunohistochemical staining of tissue specimens from our patient cohort.

CONCLUSIONS

CD200 is commonly expressed on circulating Sezary cells, a feature that can potentially improve the diagnostic value of flow cytometry for assessment of T-cell neoplasms.

Local adenoviral delivery of soluble CD200R-Ig enhances antitumor immunity by inhibiting CD200-β-catenin-driven M2 macrophage

CD200 is known as an immune checkpoint molecule that inhibits innate immune cell activation. Using a head and neck squamous cell carcinoma (HNSCC) model, we sought to determine whether localized delivery of adenovirus-expressing sCD200R1-Ig, the soluble extracellular domain of CD200R1, enhances antitumor immunity. Mouse-derived bone marrow cells and M1/M2-like macrophages were cocultured with tumor cells and analyzed for macrophage polarization. As an in vivo model, C57BL/6 mice were subcutaneously injected with MEER/CD200^High cells, CD200-overexpressing mouse HNSCC cells. Adenovirus-expressing sCD200R1-Ig (Ad5sCD200R1) was designed, and its effect was tested. Components in the tumor-immune microenvironment (TIME) were quantified using flow cytometry. CD200 promoted tumor growth and induced the expression of immune-related genes, especially macrophage colony-stimulating factor (M-CSF). Interestingly, CD200 induced M2-like polarization both in vitro and in vivo. Consequently, CD200 recruited more regulatory T (Treg) cells and fewer CD8⁺ effector T cells. These effects were effectively abolished by local injection of Ad5sCD200R1. These protumor effects of CD200 were driven through the β-catenin/NF-κB/M-CSF axis. CD200 upregulated PD-L1, and the combined targeting of CD200 and PD-1 thus showed synergy. The immune checkpoint CD200 upregulated immune-related genes through β-catenin signaling, reprogrammed the TIME, and exerted protumor effects. Ad5sCD200R1 injection could be an effective targeted strategy to enhance antitumor immunoediting.

[Differences in anatomical area-specific wound healing in hidradenitis suppurativa/acne inversa after surgery]

BACKGROUND

Hidradenitis suppurativa/acne inversa is an inflammatory, debilitating disease for which wide local excision of the affected area with secondary wound healing is considered the treatment of first choice for the inactive scarring form or after adequate anti-inflammatory medical treatment.

OBJECTIVES

In this study, we aimed to assess the duration of complete secondary wound healing after surgical intervention for hidradenitis suppurativa/acne inversa.

MATERIALS & METHODS

Twenty-three surgical procedures in 17 consecutive patients (eight female, nine male) were evaluated for duration of secondary wound healing at axillary or anogenital/inguinal sites. To investigate the contribution of hair follicle bulge progenitor cells in wound re-epithelialization, tissue samples of lesional and perilesional skin were analysed for expression of the stem cell marker, cytokeratin 15 (CK15), and CD200, a marker for human follicular stem cells that resides in the bulge area.

RESULTS

Initial wound size did not differ significantly between surgical wounds in the axillary (mean: 30.0 cm² ± 5.4) and anogenital/inguinal (mean: 35.3 cm² ± 5.7) region. However, healing time to complete wound closure was almost twice as fast in the anogenital/inguinal (mean: 132 days ± 10.4) than axilla area (mean: 254 days ± 39.1; p < 0.01). The accelerated wound healing in the anogenital/inguinal region was accompanied by significantly enhanced CK15 and CD200 expression, compared to axillary wounds (p < 0.05).

CONCLUSION

The anogenital/inguinal region showed significantly faster secondary wound healing after surgical intervention for hidradenitis suppurativa/acne inversa compared to axillary wounds. We suspect differences in pilosebaceous unit density and thus hair follicle progenitor cells (as mirrored by CK15 and CD200 expression) to be the main driver behind this finding.

Immunohistochemical Expression of CD200 in Renal Cell Carcinoma

Background and Objectives:

Renal cell carcinoma (RCC) is the most common malignant renal neoplasm in adults. CD200 is a transmembrane protein and is a promising target for cancer immunotherapy. The aim of this study is to assess the CD200 expression in RCC.

Materials and Methods:

Eighty paraffin-embedded radical nephrectomy specimens, diagnosed with RCC were evaluated immunohistochemically for CD200 expression.

Results:

Out of eighty cases studied, CD200 was expressed in n = 73 cases (91.25%) with high intensity in 27 cases (33.75%), moderate intensity in 22 cases (27.5%), and mild intensity in 24 cases (30%). No staining was observed in the adjacent apparently normal renal tissue in all examined sections. No significant relationship was found between CD200 expression and the gender, tumor size, tumor side, histologic type, nuclear grade, T stage, and tumor necrosis.

Conclusion:

CD200 expression in most of the studied cases of RCC may refer to the potential therapeutic of anti-CD200 antibody for this cancer.

Multiplex Quantitative Analysis of Tumor-Infiltrating Lymphocytes, Cancer-Associated Fibroblasts, and CD200 in Pancreatic Cancer

Pancreatic cancer is marked by a desmoplastic tumor microenvironment and low tumor immunogenicity, making it difficult for immunotherapy drugs to improve outcomes for patients. Tumor-infiltrating lymphocytes (TILs) and cancer-associated fibroblasts (CAFs) are seen in the tumor microenvironment of patients with pancreatic ductal adenocarcinoma (PDAC). In this work, we sought to characterize the expression levels and potential prognostic value of TILs (CD4, CD8, and CD20) and CAFs (Thy-1, FAP, and SMA) in a large retrospective cohort of PDAC patients. Additionally, we investigated the expression levels and prognostic significance of CD200, an immunoinhibitory protein that has shown interest as a potential target for immune checkpoint blockade. We measured the expression levels of these seven proteins with multiplexed immunofluorescence staining and quantitative immunofluorescence (QIF). We found CD8 and FAP to be independent predictors of progression-free survival and overall survival. CD200 was found to be heterogeneously expressed in both the tumor and stromal compartments of PDAC, with the majority of patients having positive stromal expression and negative tumor expression. This work demonstrates the potential clinical utility of CD8 and FAP in PDAC patients, and it sheds light on the expression patterns of CD200 in pancreatic cancer as the protein is being tested as a target for immune checkpoint blockade.

CD200 Blockade Modulates Tumor Immune Microenvironment but Fails to Show Efficacy in Inhibiting Tumor Growth in a Murine Model of Melanoma

CD200-CD200R pathway regulates immune responses and has been implicated in the pathogenesis of a number of cancer types. CD200 blockade is considered a strategy for immunotherapy of CD200-positive cancers such as melanoma. Thus, it is critical to understand the potential impacts of CD200 blockade in a more human relevant tumor model. In this study, we evaluated these issues using the CD200⁺ Yumm1.7 mouse melanoma model. Yumm1.7 cells bear Braf/Pten mutations resembling human melanoma. We found that Yumm1.7 tumors grow significantly faster in CD200R^–/– mice compared to wild type mice. Analysis of tumor immune microenvironment (TIME) revealed that tumors from CD200R^–/– or anti-CD200 treated mice had downregulated immune cell contents and reduced TCR clonality compared to tumors from untreated wild type mice. T cells also showed impaired effector functions, as reflected by reduced numbers of IFN-γ⁺ and TNF-α⁺ T cells. Mechanistically, we found upregulation of the CCL8 gene in CD200R^–/– tumors. In vitro co-culture experiments using Yumm1.7 tumor cells with bone marrow derived macrophages (BMDM) from WT and CD200R^–/– mice confirmed upregulation of macrophage CCL8 in the absence of CD200-CD200R interaction. Finally, we found that anti-CD200 therapy failed to show efficacy either alone or in combination with checkpoint inhibitors such as anti-PD-1 or anti-CTLA4 in inhibiting Yumm1.7 tumor growth. Given that CD200R-deficiency or anti-CD200 treatment leads to reduced T cell responses in TME, using blockade of CD200 as an immunotherapy for cancers such as melanoma should be practiced with caution.

CD200 expression in hematopoietic neoplasms: Beyond a marker for diagnosis of B-cell neoplasms

CD200 (OX-2) is expressed in myeloid cells, B cells, subsets of T cells and on other normal and neoplastic non-hematopoietic cells. It interacts with CD200R and has a suppressive effect on T cells immune mediated response. We aimed to review CD200 expression and its role in the immune evasion of non-B cell hematopoietic neoplasms. In acute myeloid leukemia, CD200 seems to be related to the worst outcome, even in diseases of good prognosis, possibly due to an immunosuppressive effect. In plasma cell myeloma studies, while some have associated CD200 expression with worst prognosis possibly due to its suppressive effect on monocyte and T cell-mediated immune response, in others CD200 appeared to be a marker of a better outcome, or even showed no impact in event-free survival (EFS). Few studies have evaluated CD200 expression in T cell neoplasms; however, it appears to be a good immunophenotypic marker for angioimmunoblastic T cell lymphoma. In conclusion, CD200 appears to be involved in the immune evasion of malignant cells, which could affect the survival of these patients.

Independent diagnostic utility of CD20, CD200, CD43 and CD45 in chronic lymphocytic leukaemia

Immunophenotyping plays a major role and is essential for establishing the diagnosis of chronic lymphocytic leukemia (CLL). Though CLL has a characteristic phenotype, diagnosis may be challenging due to immunophenotypic overlap with other B cell non-Hodgkin's lymphomas (B-NHL). Markers like CD200, CD43, CD20 and CD45 were found valuable in CLL and we investigated their diagnostic efficiency and accuracy in 174 patients with leukemic B-NHL. On the integration of four markers by a scoring system, 96% (49/51) of CLL cases showed a score of 3 or 4 and 90% (36/40) of non-CLL cases had a score of 0 or 1. This scoring system for CLL diagnosis showed a sensitivity of 98.2% and 96% in the analytical cohort and validation cohort respectively, which was significantly higher than the classical Matutes score. Hence we strongly suggest considering the expression of CD200, CD20, CD43 and CD45 in the diagnosis of B-NHL cases.

Novel Combination of Surface Markers for the Reliable and Comprehensive Identification of Human Thymic Epithelial Cells by Flow Cytometry: Quantitation and Transcriptional Characterization of Thymic Stroma in a Pediatric Cohort

Thymic epithelial cells (TECs) are essential in supporting the development of mature T cells from hematopoietic progenitor cells and facilitate their lineage-commitment, proliferation, T-cell receptor repertoire selection and maturation. While animal model systems have greatly aided in elucidating the contribution of stromal cells to these intricate processes, human tissue has been more difficult to study, partly due to a lack of suitable surface markers comprehensively defining human TECs. Here, we conducted a flow cytometry based surface marker screen to reliably identify and quantify human TECs and delineate medullary from cortical subsets. These findings were validated by transcriptomic and histologic means. The combination of EpCAM, podoplanin (pdpn), CD49f and CD200 comprehensively identified human TECs and not only allowed their reliable distinction in medullary and cortical subsets but also their detailed quantitation. Transcriptomic profiling of each subset in comparison to fibroblasts and endothelial cells confirmed the identity of the different stromal cell subsets sorted according to the proposed strategy. Our dataset not only demonstrated transcriptional similarities between TEC and cells of mesenchymal origin but furthermore revealed a subset-specific distribution of a specific set of extracellular matrix-related genes in TECs. This indicates that TECs significantly contribute to the distinct compartmentalization - and thus function - of the human thymus. We applied the strategy to quantify TEC subsets in 31 immunologically healthy children, which revealed sex-specific differences of TEC composition early in life. As the distribution of mature CD4- or CD8-single-positive thymocytes was correspondingly altered, the composition of the thymic epithelial compartment may directly impact on the CD4-CD8-lineage choice of thymocytes. We prove that the plain, reliable strategy proposed here to comprehensively identify human TEC subpopulations by flow cytometry based on surface marker expression is suitable to determine their frequency and phenotype in health and disease and allows sorting of live cells for downstream analysis. Its use reaches from a reliable diagnostic tool for thymic biopsies to improved phenotypic characterization of thymic grafts intended for therapeutic use.

CD200 Baseline Serum Levels Predict Prognosis of Chronic Lymphocytic Leukemia

Simple Summary

This study aimed at investigating the prognostic significance of the soluble form of CD200 antigen evaluated at diagnosis in patients with chronic lymphocytic leukemia (CLL). In a large cohort of patients, we found that more aggressive features and a worse prognosis are correlated with higher baseline serum levels of CD200. These data support the relevant role of CD200 not only as a diagnostic tool but also as a prognostic indicator and a potential therapeutic target in CLL.

Abstract

Membrane-bound CD200 is overexpressed in chronic lymphocytic leukemia (CLL), and there is some evidence that its soluble ectodomain (sCD200) could also be involved in the pathophysiology and the disease. However, very little is known about sCD200’s prognostic significance. sCD200 was tested at diagnosis in 272 patients with CLL and in 78 age- and sex-matched healthy subjects using a specific human CD200 (OX-2 membrane glycoprotein) ELISA kit. A significantly higher concentration of sCD200 was found in CLL patients compared to controls. In our cohort, sCD200 was significantly higher in patients who were older than 66 years, with Binet stage C, unmutated IgVH and unfavorable (del11q or del17p) FISH. Time-to-first treatment and overall survival were significantly shorter in patients with higher sCD200 concentration, using as a cut-off 1281 pg/mL, the median value for sCD200 concentration in the whole CLL cohort. However, the prognostic impact of sCD200 was not confirmed in multivariate analysis. Baseline sCD200 values appeared to have an impact on the response to chemotherapy or chemo-immunotherapy, but not to targeted agents. Collectively, our data show that sCD200 serum levels correlate with more aggressive clinical and biological features and are able to predict a worse prognosis. This work supports the relevant role of CD200 not only as a diagnostic tool but also as a prognostic indicator and a potential therapeutic target in CLL.

Immunomodulatory effects of phytosomal curcumin on related-micro RNAs, CD200 expression and inflammatory pathways in dental pulp stem cells

Human dental pulp stem cells (hDPSCs) have significant potential of immunomodulatory for therapeutic and regenerative biomedical applications compared to other mesenchymal stem cells (MSCs). Nowadays, alteration of gene expression is an important way to improve the performance of MSCs in the clinic. MicroRNAs (miRs) and CD200 are known to modulate the immune system in MSCs. Curcumin is famous for its anti-inflammatory impacts. Phytosomal curcumin (PC) is a nanoparticle synthesized from curcumin that removes the drawbacks of curcumin. The purpose of this research was to assess the effects of PC on the expression of the CD200 and four key miRNAs in immune system. PC (30 μM) treatment of hDPSCs could ameliorate their immunoregulatory property, presented by reduced expressions of miR-21, miR-155 and miR-126, as well as enhanced expressions of miR-23 and CD200. The PC was also able to reduce PI3K\AKT1\NF-κB expressions that were target genes for these miRs and involved in inflammatory pathways. Moreover, PC was more effective than curcumin in improving the immune modulation of hDPSCs. Evidence in this study suggested that PC mediates immunoregulatory activities in hDPSC via miRs and CD200 to regulate PI3K\AKT1\NF-κB signalling pathways, which may provide a theoretical basis for PC in the treatment of many diseases. SIGNIFICANCE OF THE STUDY: Autoimmune diseases or tooth caries are partly attributed to global health problems and their common drug treatments have several side effects. The goal of this study is dentin regeneration and autoimmune diseases treatment via stem cell-based approaches with phytosomal curcumin (PC), for the first time. Because dental pulp stem cells have unique advantages (including higher immunomodulatory capacity) over other mesenchymal stem cells, we considered them the best option for treating these diseases. Using PC, we try to increase the immunomodulatory properties of these cells.

The CD200/CD200R expression level and its mechanism of action in hematological malignancy patients

OBJECTIVE

To explore the CD200/CD200R expression level in the peripheral blood mononuclear cells (PBMC) of hematological malignancy patients and to analyze its mechanism of action.

METHODS

Thirty hematological malignancy patients who were hospitalized in our hospital from June 2019 to December 2019 were recruited as the study cohort and placed in the disease group, and 30 healthy people were also recruited for the study and placed in the healthy control group. The CD200/CD200R expression level in the two groups' peripheral blood was measured using real-time fluorescent quantitative PCR, and enzyme-linked immunosorbent assays were used to measure the interleukin 17 (IL-17), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) expression levels in the two groups' peripheral blood. We monitored the effects of the effective treatment on the CD200/CD200R level in the hematological malignancy patients.

RESULTS

Compared with the healthy group, the CD200 and CD200R mRNA expression level in the PBMC of the disease group was down-regulated, but the IL-17, TNF-α and IFN-γ expression levels in the peripheral blood plasma were up-regulated, and the differences were statistically significant (P < 0.001). The CD200 and CD200R levels showed a negative correlation with the IL-17, TNF-α, and IFN-γ expression levels in the hematological malignancy patients (P < 0.001). The CD200/CD200R expression level was significantly increased in the PBMC of the effectively treated hematological malignancy patients compared with their pre-treatment expression level, and the difference was statistically significant (P < 0.001).

CONCLUSION

CD200/CD200R exhibits a low expression level in hematological malignancy patients, reducing the inhibitory effect on the inflammatory factor expressions, enhancing the inflammatory factors, and mediating the occurrence and development of hematological malignancies.

Impact of Concomitant Aberrant CD200 and BCL2 Overexpression on Outcome of Acute Myeloid Leukemia: A Cohort Study from a Single Center

Objective:

CD200 and BCL2 overexpression is independently associated with inferior survival in acute myeloid leukemia (AML), and these two factors are frequently co-expressed; however, no data are available on the role of concomitant aberrant CD200 and BCL2 expression on outcome of AML patients. We aimed to elucidate the prognostic role of CD200/BCL2 co-expression and its association with specific leukemia subsets.

Materials and Methods:

We analyzed 242 adult AML patients uniformly treated with intensive chemotherapy, evaluating the impact of CD200 and BCL2 expression on complete remission (CR), disease-free survival, and overall survival (OS).

Results:

CD200 and BCL2 were expressed in 139 (57.4%) and 137 (56.6%) cases, respectively, with 92 patients (38%) displaying double positivity (DP), 58 (24%) displaying double negativity (DN), and 92 patients expressing only either CD200 (n=47) or BCL2 (n=45). CR was achieved in 71% of cases, being less frequent in DP patients (60%) compared to other groups (76%-81%, p<0.001). In the whole population 3-year OS was 44%, being lower in DP patients (28%) than in patients with single CD200 or BCL2 expression (47%) or DN cases (60%; p=0.004). Other factors associated with worse OS were advanced age, CD34 positivity, secondary AML, and high white blood cell count at diagnosis; combining these 4 factors with CD200/BCL2 DP, we identified 6 groups with significantly different rates of survival (3-year OS ranging from 90% to 0%).

Conclusion:

Our data support a synergistic effect of CD200 and BCL2 in AML cells, conferring an enhanced survival capacity in a permissive microenvironment and resulting in worse prognosis.

The CD200 Regulates Inflammation in Mice Independently of TNF-α Production

Inflammatory bowel disease is characterized by the infiltration of immune cells and chronic inflammation. The immune inhibitory receptor, CD200R, is involved in the downregulation of the activation of immune cells to prevent excessive inflammation. We aimed to define the role of CD200R ligand-CD200 in the experimental model of intestinal inflammation in conventionally-reared mice. Mice were given a dextran sodium sulfate solution in drinking water. Bodyweight loss was monitored daily and the disease activity index was calculated, and a histological evaluation of the colon was performed. TNF-α production was measured in the culture of small fragments of the distal colon or bone marrow-derived macrophages (BMDMs) cocultured with CD200⁺ cells. We found that Cd200^-/- mice displayed diminished severity of colitis when compared to WT mice. Inflammation significantly diminished CD200 expression in WT mice, particularly on vascular endothelial cells and immune cells. The co-culture of BMDMs with CD200⁺ cells inhibited TNF-α secretion. In vivo, acute colitis induced by DSS significantly increased TNF-α secretion in colon tissue in comparison to untreated controls. However, Cd200^-/- mice secreted a similar level of TNF-α to WT mice in vivo. CD200 regulates the severity of DSS-induced colitis in conventionally-reared mice. The presence of CD200⁺ cells decreases TNF-α production by macrophages in vitro. However, during DDS-induced intestinal inflammation secretion of TNF-α is independent of CD200 expression.

Overexpression of Endogenous Retroviruses and Malignancy Markers in Neuroblastoma Cell Lines by Medium-Induced Microenvironmental Changes

Neuroblastoma (NB) is the commonest solid tumor outside the central nervous system in infancy and childhood with a unique biological heterogeneity. In patients with advanced, metastasizing neuroblastoma, treatment failure and poor prognosis is often marked by resistance to chemo- or immunotherapy. Thus, identification of robust biomarkers seems essential for understanding tumor progression and developing effective therapy. Here, we have studied the expression of human endogenous retroviruses (HERV) as potential targets in NB cell lines during stem-cell medium-induced microenvironmental change. Quantitative PCR revealed that relative expression of the HERV-K family and HERV-W1 ENV were increased in all three NB cell lines after incubation in stem-cell medium. Virus transcriptome analyses revealed the transcriptional activation of three endogenous retrovirus elements: HERV-R ENV (ERV3-1), HERV-E1 and HERV-Fc2 ENV (ERVFC1-1). Known malignancy markers in NB, e.g. proto-oncogenic MYC or MYCN were expressed highly heterogeneously in the three investigated NB cell lines with up-regulation of MYC and MYCN upon medium-induced microenvironmental change. In addition, SiMa cells exclusively showed a phenotype switching from loosely-adherent monolayers to low proliferating grape-like cellular aggregates, which was accompanied by an enhanced CD133 expression. Interestingly, the overexpression of HERV was associated with a significant elevation of immune checkpoint molecule CD200 in both quantitative PCR and RNA-seq analysis suggesting tumor escape mechanism in NB cell lines after incubation in serum-free stem cell medium.

Cannabinoid receptor-1 has an effect on CD200 under rotenone and alpha-synuclein induced stress

Decades after identifying cannabinoids and their beneficial effects on Parkinson's disease (PD), many gaps are still missing. Although, CB₂-dependent actions have been shown as underlying positive effects of cannabinoid treatment, in recent years, another receptor of cannabinoids, CB₁, emerged as a valuable player in cannabinoid-induced neuroprotection. Remarkably, the effects of CB₁ are mainly related to immune cells in the CNS, microglia, and astrocytes. However, oxidative stress, α-syn accumulation, and immune disbalance are essential aspects of both neurons and glial cells. Therefore, in this study, we investigated the effects of the CB₁ on both α-syn and rotenone-treated SH-SY5Y and C8-D1A cells. ACEA and AM-251 were used as CB₁ agonists and antagonists. Cell viability, IL-1β, IL-6, TNF-α levels, and CD200 expressions were determined in culture mediums. Our results demonstrated that preformed fibril form (pFF) of α-syn did not cause any significant change in SH-SY5Y cells compared to C8-D1A cells. Rotenone significantly increased the expression of IL-1β, IL-6, and TNF-α levels in both cells. pFF α-syn and rotenone treatment caused a decrease in CD200 expression. Surprisingly both ACEA and AM-251 alleviated rotenone-induced increase in cytokine levels in both cell lines. Although ACEA prevented pFF α-syn induced increase in cytokine levels and decrease in CD200 expression in C8-D1A cells, AM-251 failed to affect CD200 expression levels. Additionally, ACEA + AM-251 abolished the protective effects of both ACEA and AM-251 against rotenone and α-syn insults in both cell lines. The current study suggests that cannabinoid receptor agonism alleviates rotenone and α-syn-dependent inflammation in neurons and astrocytes.

Use of an anti-CD200-blocking antibody improves immune responses to AML in vitro and in vivo

Treatment of relapsed/resistant acute myeloid leukaemia (AML) remains a significant area of unmet patient need, the outlook for most patients remaining extremely poor. A promising approach is to augment the anti-tumour immune response in these patients; most cancers do not activate immune effector cells because they express immunosuppressive ligands. We have previously shown that CD200 (an immunosuppressive ligand) is overexpressed in AML and confers an inferior overall survival compared to CD200low/neg patients. Here we show that a fully human anti-CD200 antibody (TTI-CD200) can block the interaction of CD200 with its receptor and restore AML immune responses in vitro and in vivo.

High CD200 Expression on T CD4+ and T CD8+ Lymphocytes as a Non-Invasive Marker of Idiopathic Pulmonary Hypertension-Preliminary Study

Pulmonary arterial hypertension (PAH) can develop subsequently to disorganized endothelial cell proliferation within the pulmonary arteriolar layers that provide mechanical limits to the pulmonary vascular bed. Although the actual factor triggering vascular endothelial proliferation remains unknown to date, genetic susceptibility, hypoxia, inflammation, as well as response to drugs and toxins have been proposed as possible contributors. Since inflammation contributes to vascular remodeling, the changed immune response is increasingly considered a plausible cause of this cardiovascular disease. The interaction of a membrane glycoprotein cluster of differentiation 200 (CD200) and its structurally similar receptor (CD200R) plays a crucial role in the modulation of the inflammatory response. Our previous studies have shown that the overexpression of the other negative co-stimulatory molecule (programmed death cell-PD-1) and its ligand-1 (PD-L1) is closely related to iPAH and the presence of Epstein-Barr virus (EBV) reactivation markers. Therefore, we considered it necessary to analyze the different types of PAH in terms of CD200 and CD200R expression and to correlate CD200/CD200R pathway expression with important clinical and laboratory parameters. The CD200/C200R-signaling pathway has not been subject to much research. We included 70 treatment-naïve, newly diagnosed patients with PAH in our study. They were further divided into subsets according to the pulmonary hypertension classification: chronic thromboembolic pulmonary hypertension (CTEPH) subset, pulmonary arterial hypertension associated with congenital heart disease (CHD-PAH), pulmonary arterial hypertension associated with connective tissue disease (CTD-PAH), and idiopathic pulmonary arterial hypertension (iPAH). The control group consisted of 20 healthy volunteers matched for sex and age. The highest percentages of T CD200+CD4+ and T CD200+CD8+ lymphocytes were observed in the group of patients with iPAH and this finding was associated with the presence of EBV DNA in the peripheral blood. Our assessment of the peripheral blood lymphocytes expression of CD200 and CD200R indicates that these molecules act as negative co-stimulators in the induction and persistence of PAH-associated inflammation, especially that of iPAH. Similar results imply that the dysregulation of the CD200/CD200R axis may be involved in the pathogenesis of several immune diseases. Our work suggests that CD200 and CD200R expression may serve to distinguish between PAH cases. Thus, CD200 and CD200R might be useful as markers in managing PAH and should be further investigated.

Quantitative Assessment of CD200 and CD200R Expression in Lung Cancer

CD200/CD200R is an immune checkpoint with broad expression patterns and a potential target for immune therapy. In this study, we assess both CD200 and CD200R expression in solid tumors, with a focus on lung cancer, and evaluate their association with clinicopathologic characteristics, mutation status, outcome, and programmed death-ligand 1 (PD-L1) expression. We used multiplexed quantitative immunofluorescence (QIF) to measure the expression of CD200 and CD200R in a total of 455 patients from three lung cancer cohorts. Using carefully validated antibodies, we performed target measurement with tyramide-based QIF panels and analyzed the data using the PM2000 microscope and AQUA software. CD200 tumor positivity was found in 29.7% of non-small cell lung cancer (NSCLC) patients and 33.3% of lung large cell neuroendocrine carcinoma (LCNEC) patients. CD200 demonstrated notable intratumoral heterogeneity. CD200R was expressed in immune cells in 25% of NSCLC and 41.3% of LCNEC patients. While CD200R is predominantly expressed in immune cells, rare tumor cell staining was seen in a highly heterogeneous pattern. CD200R expression in the stromal compartment was significantly higher in patients with squamous differentiation (p < 0.0001). Neither CD200 nor CD200R were associated with other clinicopathologic characteristics or mutation status. Both biomarkers were not prognostic for disease-free or overall survival in NSCLC. CD200 showed moderate correlation with PD-L1. CD200/CD200R pathway is frequently expressed in lung cancer patients. Differential expression patterns of CD200 and CD200R with PD-L1 suggest a potential role for targeting this pathway alone in patients with NSCLC.

Electroacupuncture Reduces Oocyte Number and Maintains Vascular Barrier Against Ovarian Hyperstimulation Syndrome by Regulating CD200

Ovarian hyperstimulation syndrome (OHSS) is a common complication caused by ovulatory stimulation therapy, which manifests as an increase in ovarian volume, an increase in the number of oocytes retrieved, and increased vascular permeability throughout the body and especially in ovarian tissue. In our previous study, we found that electroacupuncture (EA) could prevent the progression of OHSS, by mainly affecting ovary. However, the specific molecules and the mechanism of this process were still unknown. In order to explore the underlying mechanism, OHSS rat model was established and EA treatment was performed, which was followed by proteomic analysis of ovaries. Results showed a significant increase in the expression level of CD200 in the ovaries of OHSS group treated with EA than those of OHSS group. Clinical data showed that the level of CD200 in follicular fluid was negatively correlated with the number of oocytes retrieved and serum E2 level. Further in vitro experiments showed a concentration-dependent role of human chorionic gonadotropin (hCG) in reducing CD200 and CD200R levels, and increasing inflammatory cytokine levels in cultured KGN cells. In human umbilical vein endothelial cells (HUVECs), the vascular barrier function was improved by CM (cultural medium from KGN cell) which treated with CD200Fc (CD200R agonist). Meanwhile, the results of in vivo experiments indicated that EA reduced the number of ovarian corpora lutea, decreased inflammatory response, and improved the vascular barrier function by increasing the expression of CD200 and CD200R in rat ovaries. These findings suggest that EA treatment may reduce oocyte number and maintain vascular barrier against OHSS through ovarian anti-inflammatory response mediated by CD200. Therefore, this study is the first to identify CD200 as a main of EA in the ovary and elucidate the possible mechanism of EA on preventing and treating OHSS, which provide a scientific basis for CD200 as an effector and indicator in EA treatment.

CD200:CD200R Interactions and Their Importance in Immunoregulation

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH₂-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.