Deficient inflammasome activation permits an exaggerated asthma phenotype in rhinovirus C-infected immature mice

Compared to other RV species, RV-C has been associated with more severe respiratory illness and is more likely to occur in children with a history of asthma or who develop asthma. We therefore inoculated 6-day-old mice with sham, RV-A1B, or RV-C15. Inflammasome priming and activation were assessed, and selected mice treated with recombinant IL-1β. Compared to RV-A1B infection, RV-C15 infection induced an exaggerated asthma phenotype, with increased mRNA expression of Il5, Il13, Il25, Il33, Muc5ac, Muc5b, and Clca1; increased lung lineage-negative CD25+CD127+ST2+ ILC2s; increased mucous metaplasia; and increased airway responsiveness. Lung vRNA, induction of pro-inflammatory type 1 cytokines, and inflammasome priming (pro-IL-1β and NLRP3) were not different between the two viruses. However, inflammasome activation (mature IL-1β and caspase-1 p12) was reduced in RV-C15-infected mice compared to RV-A1B-infected mice. A similar deficiency was found in cultured macrophages. Finally, IL-1β treatment decreased RV-C-induced type 2 cytokine and mucus-related gene expression, ILC2s, mucous metaplasia, and airway responsiveness but not lung vRNA level. We conclude that RV-C induces an enhanced asthma phenotype in immature mice. Compared to RV-A, RV-C-induced macrophage inflammasome activation and IL-1β are deficient, permitting exaggerated type 2 inflammation and mucous metaplasia.

CISH constrains the tuft-ILC2 circuit to set epithelial and immune tone

Innate lymphoid cells (ILCs) are tissue-resident effectors poised to activate rapidly in response to local signals such as cytokines. To preserve homeostasis, ILCs must employ multiple pathways, including tonic suppressive mechanisms, to regulate their primed state and prevent inappropriate activation and immunopathology. Such mechanisms remain incompletely characterized. Here we show that cytokine-inducible SH2-containing protein (CISH), a suppressor of cytokine signaling (SOCS) family member, is highly and constitutively expressed in type 2 innate lymphoid cells (ILC2s). Mice that lack CISH either globally or conditionally in ILC2s show increased ILC2 expansion and activation, in association with reduced expression of genes inhibiting cell-cycle progression. Augmented proliferation and activation of CISH-deficient ILC2s increases basal and inflammation-induced numbers of intestinal tuft cells and accelerates clearance of the model helminth, Nippostrongylus brasiliensis, but compromises innate control of Salmonella typhimurium. Thus, CISH constrains ILC2 activity both tonically and after perturbation, and contributes to the regulation of immunity in mucosal tissue.

Childhood Adiposity Associated With Expanded Effector Memory CD8+ and Vδ2+Vγ9+ T Cells

CONTEXT

Adult obesity is associated with chronic low-grade inflammation and may give rise to future chronic disease. However, it is unclear whether adiposity-related inflammation is already apparent in childhood.

OBJECTIVE

To study associations between child adiposity measures with circulating monocytes and naive and memory subsets in CD4, CD8, and γδ T cell lineages.

METHODS

Ten-year-old children (n = 890) from the Generation R Cohort underwent dual-energy x-ray absorptiometry and magnetic resonance imaging for body composition (body mass index [BMI], fat mass index [FMI], android-to-gynoid fat mass ratio, visceral fat index, liver fat fraction). Blood samples were taken for detailed immunophenotyping of leukocytes by 11-color flow cytometry.

RESULTS

Several statistically significant associations were observed. A 1-SD increase in total FMI was associated with +8.4% (95% CI 2.0, 15.2) Vδ2+Vγ9+ and +7.4% (95% CI 2.4, 12.5) CD8+TEMRO cell numbers. A 1-SD increase in visceral fat index was associated with +10.7% (95% CI 3.3, 18.7) Vδ2+Vγ9+ and +8.3% (95% CI 2.6, 14.4) CD8+TEMRO cell numbers. Higher android-to-gynoid fat mass ratio was only associated with higher Vδ2+Vγ9+ T cells. Liver fat was associated with higher CD8+TEMRO cells but not with Vδ2+Vγ9+ T cells. Only liver fat was associated with lower Th17 cell numbers: a 1-SD increase was associated with -8.9% (95% CI -13.7, -3.7) Th17 cells. No associations for total CD8+, CD4+ T cells, or monocytes were observed. BMI was not associated with immune cells.

CONCLUSION

Higher Vδ2+Vγ9+ and CD8+TEMRO cell numbers in children with higher visceral fat index could reflect presence of adiposity-related inflammation in children with adiposity of a general population.

Integration of T helper and BCR signals governs enhanced plasma cell differentiation of memory B cells by regulation of CD45 phosphatase activity

Humoral immunity relies on the efficient differentiation of memory B cells (MBCs) into antibody-secreting cells (ASCs). T helper (Th) signals upregulate B cell receptor (BCR) signaling by potentiating Src family kinases through increasing CD45 phosphatase activity (CD45 PA). In this study, we show that high CD45 PA in MBCs enhances BCR signaling and is essential for their effective ASC differentiation. Mechanistically, Th signals upregulate CD45 PA through intensifying the surface binding of a CD45 ligand, Galectin-1. CD45 PA works as a sensor of T cell help and defines high-affinity germinal center (GC) plasma cell (PC) precursors characterized by IRF4 expression in vivo. Increasing T cell help in vitro results in an incremental CD45 PA increase and enhances ASC differentiation by facilitating effective induction of the transcription factors IRF4 and BLIMP1. This study connects Th signals with BCR signaling through Galectin-1-dependent regulation of CD45 PA and provides a mechanism for efficient ASC differentiation of MBCs.

Polyamine metabolism is a central determinant of helper T cell lineage fidelity

Polyamine synthesis represents one of the most profound metabolic changes during T cell activation, but the biological implications of this are scarcely known. Here, we show that polyamine metabolism is a fundamental process governing the ability of CD4+ helper T cells (TH) to polarize into different functional fates. Deficiency in ornithine decarboxylase, a crucial enzyme for polyamine synthesis, results in a severe failure of CD4+ T cells to adopt correct subset specification, underscored by ectopic expression of multiple cytokines and lineage-defining transcription factors across TH cell subsets. Polyamines control TH differentiation by providing substrates for deoxyhypusine synthase, which synthesizes the amino acid hypusine, and mice in which T cells are deficient for hypusine develop severe intestinal inflammatory disease. Polyamine-hypusine deficiency caused widespread epigenetic remodeling driven by alterations in histone acetylation and a re-wired tricarboxylic acid (TCA) cycle. Thus, polyamine metabolism is critical for maintaining the epigenome to focus TH cell subset fidelity.

Hypoxia enhances ILC3 responses through HIF-1α-dependent mechanism

Group 3 innate lymphoid cells (ILC3) have a prominent role in the maintenance of intestine mucosa homeostasis. The hypoxia-inducible factor (HIF) is an important modulator of immune cell activation and a key mechanism for cellular adaptation to oxygen deprivation. However, its role on ILC3 is not well known. In this study, we investigated how a hypoxic environment modulates ILC3 response and the subsequent participation of HIF-1 signaling in this process. We found increased proliferation and activation of intestinal ILC3 at low oxygen levels, a response that was phenocopied when HIF-1α was chemically stabilized and was reversed when HIF-1 was blocked. The increased activation of ILC3 relied on a HIF-1α-dependent transcriptional program, but not on mTOR-signaling or a switch to glycolysis. HIF-1α deficiency in RORyt compartment resulted in impaired IL-17 and IL-22 production by ILC3 in vivo, which reflected in a lower expression of their target genes in the intestinal epithelium and an increased susceptibility to Clostridiodes difficile infection. Taken together, our results show that HIF-1α activation in intestinal ILC3 is relevant for their functions in steady state and infectious conditions.

CARD9 Deficiency Increases Hippocampal Injury Following Acute Neurotropic Picornavirus Infection but Does Not Affect Pathogen Elimination

Neurotropic viruses target the brain and contribute to neurologic diseases. Caspase recruitment domain containing family member 9 (CARD9) controls protective immunity in a variety of infectious disorders. To investigate the effect of CARD9 in neurotropic virus infection, CARD9^−/− and corresponding C57BL/6 wild-type control mice were infected with Theiler’s murine encephalomyelitis virus (TMEV). Brain tissue was analyzed by histology, immunohistochemistry and molecular analyses, and spleens by flow cytometry. To determine the impact of CARD9 deficiency on T cell responses in vitro, antigen presentation assays were utilized. Genetic ablation of CARD9 enhanced early pro-inflammatory cytokine responses and accelerated infiltration of T and B cells in the brain, together with a transient increase in TMEV-infected cells in the hippocampus. CARD9^−/− mice showed an increased loss of neuronal nuclear protein⁺ mature neurons and doublecortin⁺ neuronal precursor cells and an increase in β-amyloid precursor protein⁺ damaged axons in the hippocampus. No effect of CARD9 deficiency was found on the initiation of CD8⁺ T cell responses by flow cytometry and co-culture experiments using virus-exposed dendritic cells or microglia-enriched glial cell mixtures, respectively. The present study indicates that CARD9 is dispensable for the initiation of early antiviral responses and TMEV elimination but may contribute to the modulation of neuroinflammation, thereby reducing hippocampal injury following neurotropic virus infection.

Clinical and molecular characteristics of COVID-19 patients with persistent SARS-CoV-2 infection

The characteristics of COVID-19 patients with persistent SARS-CoV-2 infection are not yet well described. Here, we compare the clinical and molecular features of patients with long duration of viral shedding (LDs) with those from patients with short duration patients (SDs), and healthy donors (HDs). We find that several cytokines and chemokines, such as interleukin (IL)-2, tumor necrosis factor (TNF) and lymphotoxin α (LT-α) are present at lower levels in LDs than SDs. Single-cell RNA sequencing shows that natural killer (NK) cells and CD14+ monocytes are reduced, while regulatory T cells are increased in LDs; moreover, T and NK cells in LDs are less activated than in SDs. Importantly, most cells in LDs show reduced expression of ribosomal protein (RP) genes and related pathways, with this inversed correlation between RP levels and infection duration further validated in 103 independent patients. Our results thus indicate that immunosuppression and low RP expression may be related to the persistence of the viral infection in COVID-19 patients.

Safety and immunological effects of recombinant canine IL-15 in dogs

Interleukin-15 (IL-15) is a pleiotropic cytokine that plays pivotal roles in innate and adaptive immunity. It is also a promising cytokine for treating cancer. Despite growing interest in its use as an immunotherapeutic, its safety and immunological effects in dogs have not been reported. In this study, healthy dogs were given recombinant canine IL-15 (rcIL-15) intravenously at a daily dose of 20 μg/kg for 8 days and monitored for 32 days to determine the safety and immunological effects of rcIL-15. The repeated administration of rcIL-15 was well tolerated, did not cause any serious side effects, and promoted the selective proliferation and activation of canine anti-cancer effector cells, including CD3⁺CD8⁺ cytotoxic T lymphocytes, CD3⁺CD5^dimCD21^-, and non-B/non-T NK cell populations, without stimulating T_reg lymphocytes. The rcIL-15 injections also stimulated the expression of molecules and transcription factors associated with the activation and effector functions of NK cells, including CD16, NKG2D, NKp30, NKp44, NKp46, perforin, granzyme B, Ly49, T-bet, and Eomes. These results suggest that rcIL-15 might be a valuable therapeutic adjuvant to improve immunity against cancer in dogs.

Coronavirus infection: An immunologists' perspective

Coronavirus infections are frequent viral infections in several species. As soon as the severe acute respiratory syndrome (SARS) appeared in the early 2000s, most of the research focused on pulmonary disease. However, disorders in immune response and organ dysfunctions have been documented. Elderly individuals with comorbidities exhibit worse outcomes in all the coronavirus that cause SARS. Disease severity in SARS-CoV-2 infection is related to severe inflammation and tissue injury, and effective immune response against the virus is still under analysis. ACE2 receptor expression and polymorphism, age, gender and immune genetics are factors that also play an essential role in patients' clinical features and immune responses and have been partially discussed. The present report aims to review the physiopathology of SARS-CoV-2 infection and propose new research topics to understand the complex mechanisms of viral infection and viral clearance.

DNA Damage Response in the Adaptive Arm of the Immune System: Implications for Autoimmunity

In complex environments, cells have developed molecular responses to confront threats against the genome and achieve the maintenance of genomic stability assuring the transfer of undamaged DNA to their progeny. DNA damage response (DDR) mechanisms may be activated upon genotoxic or environmental agents, such as cytotoxic drugs or ultraviolet (UV) light, and during physiological processes requiring DNA transactions, to restore DNA alterations that may cause cellular malfunction and affect viability. In addition to the DDR, multicellular organisms have evolved specialized immune cells to respond and defend against infections. Both adaptive and innate immune cells are subjected to DDR processes, either as a prerequisite to the immune response, or as a result of random endogenous and exogenous insults. Aberrant DDR activities have been extensively studied in the immune cells of the innate arm, but not in adaptive immune cells. Here, we discuss how the aberrant DDR may lead to autoimmunity, with emphasis on the adaptive immune cells and the potential of therapeutic targeting.

Kidney GATA3+ regulatory T cells play roles in the convalescence stage after antibody-mediated renal injury

FoxP3+ regulatory T cells (Tregs) play crucial roles in peripheral immune tolerance. In addition, Tregs that reside or accumulate in nonlymphoid tissues, called tissue Tregs, exhibit tissue-specific functions and contribute to the maintenance of tissue homeostasis and repair. In an experimental mouse model of crescentic glomerulonephritis induced by an anti-glomerular basement membrane antibody, Tregs started to accumulate in the kidney on day 10 of disease onset and remained at high levels (~30-35% of CD4+ T cells) during the late stage (days 21-90), which correlated with stable disease control. Treg depletion on day 21 resulted in the relapse of renal dysfunction and an increase in Th1 cells, suggesting that Tregs are essential for disease control during the convalescence stage. The Tregs that accumulated in the kidney showed tissue Treg phenotypes, including high expression of GATA3, ST2 (the IL33 receptor subunit), amphiregulin (Areg), and PPARγ. Although T-bet+ Tregs and RORγt+ Tregs were observed in the kidney, GATA3+ Tregs were predominant during the convalescence stage, and a PPARγ agonist enhanced the accumulation of GATA3+ Tregs in the kidney. To understand the function of specific genes in kidney Tregs, we developed a novel T cell transfer system to T cell-deficient mice. This experiment demonstrates that ST2, Areg, and CCR4 in Tregs play important roles in the accumulation of GATA3+ Tregs in the kidney and in the amelioration of renal injury. Our data suggest that GATA3 is important for the recruitment of Tregs into the kidney, which is necessary for convalescence after renal tissue destruction.

Group 3 Innate Lymphoid Cells Program a Distinct Subset of IL-22BP-Producing Dendritic Cells Demarcating Solitary Intestinal Lymphoid Tissues

Solitary intestinal lymphoid tissues such as cryptopatches (CPs) and isolated lymphoid follicles (ILFs) constitute steady-state activation hubs containing group 3 innate lymphoid cells (ILC3) that continuously produce interleukin (IL)-22. The outer surface of CPs and ILFs is demarcated by a poorly characterized population of CD11c⁺ cells. Using genome-wide single-cell transcriptional profiling of intestinal mononuclear phagocytes and multidimensional flow cytometry, we found that CP- and ILF-associated CD11c⁺ cells were a transcriptionally distinct subset of intestinal cDCs, which we term CIA-DCs. CIA-DCs required programming by CP- and ILF-resident CCR6⁺ ILC3 via lymphotoxin-β receptor signaling in cDCs. CIA-DCs differentially expressed genes associated with immunoregulation and were the major cellular source of IL-22 binding protein (IL-22BP) at steady state. Mice lacking CIA-DC-derived IL-22BP exhibited diminished expression of epithelial lipid transporters, reduced lipid resorption, and changes in body fat homeostasis. Our findings provide insight into the design principles of an immunoregulatory checkpoint controlling nutrient absorption.

Inflammatory status might direct ILC and NK cells to IL-17 expressing ILC3 and NK subsets in Behcet's disease

Innate lymphoid cells (ILCs) are lymphoid cells that have important effector and regulatory functions in innate immunity and tissue remodeling. Uncontrolled activation and proliferation of ILCs can contribute to inflammatory autoimmune diseases. Behcet's disease (BD) is a complex systemic inflammatory disorder of unknown etiology. It has been shown that natural killer (NK) cells may play an immunoregulatory role in BD, however the role of ILCs is unknown. In this study, the levels and functions of ILCs and NK cell subsets in BD patients were investigated. Cell surface and cytotoxic granules (perforin and granzyme) expression of NK cells and ILCs were evaluated and labeled according to whole blood lysing protocol in peripheral blood samples obtained from the patients and healthy subjects. Cytokine levels of NK cells were investigated in stimulated peripheral blood mononuclear cells. All data were analyzed by flow cytometry. Total ILC and ILC3⁺ cells were increased in active BD patients compared to inactive BD patients and healthy subjects. There was no significant difference between the patients and healthy subjects regarding NK cell surface and intracellular molecule expression. Although, an increase in IFN-γ and IL-17, and a decrease in IL-4 levels were observed in CD56^dim NK cell subset of BD patients. Recent studies showed increased neutrophilic infiltration and IL-17 secreting Th17 cells in BD patients. It is known that ILC3⁺cells are similar to Th17 subset regarding their cytokine profile and transcription factor expression patterns. Results of current study may suggest that inflammatory microenvironment in BD patients might direct ILC cells to differentiate into ILC3⁺ subset, and IL-17 released by NK cells might have a role in neutrophilic infiltration.

Epigenetic modulation of immune synaptic-cytoskeletal networks potentiates γδ T cell-mediated cytotoxicity in lung cancer

γδ T cells are a distinct subgroup of T cells that bridge the innate and adaptive immune system and can attack cancer cells in an MHC-unrestricted manner. Trials of adoptive γδ T cell transfer in solid tumors have had limited success. Here, we show that DNA methyltransferase inhibitors (DNMTis) upregulate surface molecules on cancer cells related to γδ T cell activation using quantitative surface proteomics. DNMTi treatment of human lung cancer potentiates tumor lysis by ex vivo-expanded Vδ1-enriched γδ T cells. Mechanistically, DNMTi enhances immune synapse formation and mediates cytoskeletal reorganization via coordinated alterations of DNA methylation and chromatin accessibility. Genetic depletion of adhesion molecules or pharmacological inhibition of actin polymerization abolishes the potentiating effect of DNMTi. Clinically, the DNMTi-associated cytoskeleton signature stratifies lung cancer patients prognostically. These results support a combinatorial strategy of DNMTis and γδ T cell-based immunotherapy in lung cancer management.

Testing Cancer Immunotherapy in a Human Immune System Mouse Model: Correlating Treatment Responses to Human Chimerism, Therapeutic Variables and Immune Cell Phenotypes

Over the past decade, immunotherapies have revolutionized the treatment of cancer. Although the success of immunotherapy is remarkable, it is still limited to a subset of patients. More than 1500 clinical trials are currently ongoing with a goal of improving the efficacy of immunotherapy through co-administration of other agents. Preclinical, small-animal models are strongly desired to increase the pace of scientific discovery, while reducing the cost of combination drug testing in humans. Human immune system (HIS) mice are highly immune-deficient mouse recipients rtpeconstituted with human hematopoietic stem cells. These HIS-mice are capable of growing human tumor cell lines and patient-derived tumor xenografts. This model allows rapid testing of multiple, immune-related therapeutics for tumors originating from unique clinical samples. Using a cord blood-derived HIS-BALB/c-Rag2nullIl2rγnullSIRPαNOD (BRGS) mouse model, we summarize our experiments testing immune checkpoint blockade combinations in these mice bearing a variety of human tumors, including breast, colorectal, pancreatic, lung, adrenocortical, melanoma and hematological malignancies. We present in-depth characterization of the kinetics and subsets of the HIS in lymph and non-lymph organs and relate these to protocol development and immune-related treatment responses. Furthermore, we compare the phenotype of the HIS in lymph tissues and tumors. We show that the immunotype and amount of tumor infiltrating leukocytes are widely-variable and that this phenotype is tumor-dependent in the HIS-BRGS model. We further present flow cytometric analyses of immune cell subsets, activation state, cytokine production and inhibitory receptor expression in peripheral lymph organs and tumors. We show that responding tumors bear human infiltrating T cells with a more inflammatory signature compared to non-responding tumors, similar to reports of "responding" patients in human immunotherapy clinical trials. Collectively these data support the use of HIS mice as a preclinical model to test combination immunotherapies for human cancers, if careful attention is taken to both protocol details and data analysis.

Immunological characterization of chimeras of high specificity antigens from Mycobacterium tuberculosis H37Rv

Tuberculosis remains a serious global health problem. BCG is the only prophylactic TB vaccine and it shows variable protective efficacy. Chimeric protein subunit vaccines hold great potential as stand-alone vaccines or heterologous BCG prime boosters. We have designed a protein chimera, PP31, by combining Mtb ESAT-6 family antigen Rv1198 and MoCo biosynthesis family antigen Rv3111. Further, PP31 was extended by addition of latency antigen Rv1813c to yield PP43. Immunization of BALB/c mice with PP31 or PP43 with FIA adjuvant elicited strong humoral immune response. Restimulation of splenocytes of the immunized mice lead to significant proliferation of lymphocytes, secretion of cytokines IFN-γ, TNF, IL-2 of the Th1 class, IL-17A of the Th17 class, and IL-6. PP31 and PP43 also induced intracellular cytokine expression (IFN-γ, TNF, and IL-2) from both CD4+-CD44high and CD8+-CD44high T-cells. Antigen-specific IFN-γ+/IL-2+ double positive CD4+ T-cells were significantly higher in case of PP43 than PP31-immunized mice and control group. PP43 showed protection equivalent to heat-inactivated BCG in response to challenge of the immunized mice with Mtb H37Ra. Based on its immunogenicity and protective efficacy, PP43 appears to be a potential candidate for further development as a subunit vaccine against TB.

A novel Cytochrome P450 26A1 expressing NK cell subset at the mouse maternal-foetal interface

Cyp26a1 had important roles in mouse embryo implantation and was highly expressed in some of NK cells at the human maternal-foetal interface in early pregnancy. However, the regulatory effect of Cyp26a1 on NK cells remains poorly understood. Through qPCR and flow cytometric assays, we found that Cyp26a1 was expressed by mouse uterine NK cells but not spleen NK cells during the peri-implantation period and there was a group of NK cells that highly expressed Cyp26a1, that is Cyp26a1+ NK cell subset. single cell-population transcriptome sequencing on Cyp26a1+ NK and Cyp26a1- NK cell subsets was performed. We found that there were 3957 differentially expressed genes in the Cyp26a1+ NK cell subset with a cut-off of fold change ≥2 and FDR < 0.01, 2509 genes were up-regulated and 1448 genes were down-regulated in Cyp26a1+ NK cell subset. Moreover, cytokine-cytokine receptor interaction signalling pathway and natural killer cell-mediated cytotoxicity signalling pathway were enriched according to KEGG pathway enrichment analysis. We further found that the expression of Gzma and Klrg1 was significantly increased and Fcgr4 was significantly decreased when inhibiting Cyp26a1. Our experimental results show that there is a novel NK cell subset of Cyp26a1+ NK cells in mouse uterus and Cyp26a1 can regulate the gene expression of Gzma, Klrg1 and Fcgr4 in the Cyp26a1+ NK cells.

BATF regulates innate lymphoid cell hematopoiesis and homeostasis

Early hematopoietic progenitors undergo sophisticated developmental processes to become committed innate lymphoid cell (ILC) progenitors and ultimately mature ILC subsets in the periphery. Basic leucine zipper ATF-like transcription factor (Batf) plays important roles in lymphocyte biology. We report here that Batf regulates the production of bone marrow ILC progenitors and maintenance of peripheral ILCs. The expression of Batf is induced during ILC development at the α-lymphoid progenitor stage in response to the cytokine IL-7. As a potential mechanism, up-regulated Batf binds and activates transcription of the Nfil3 gene to promote ILC hematopoiesis. Batf is necessary to maintain normal numbers of early and late ILC progenitors in the bone marrow and mature ILC1, ILC2, ILC3, and NK cells in most peripheral tissues. Batf deficiency causes ILC lymphopenia, leading to defective ILC responses to inflammatory cytokines and defective immunity to enteric bacterial infections. Thus, Batf plays critical roles in bone marrow hematopoiesis, peripheral homeostasis, and effector functions of ILCs.

Long-term effects of intensive B cell depletion therapy in severe cases of IgG4-related disease with renal involvement

IgG4-related disease (IgG4-RD) is an immune-mediated disorder often showing elevated serum IgG4 concentrations, dense T and B lymphocyte infiltration, and IgG4-positive plasma cells and storiform fibrosis. We prospectively evaluated for 4 years 5 patients with histologically proven IgG4-RD of whom 3 had tubulointerstitial nephritis (TIN) and 2 had retroperitoneal fibrosis (RPF). They received an intensive B depletion therapy with rituximab. The estimated glomerular filtration rate of TIN patients after 1 year increased from 9 to 24 ml/min per 1.73 m2. IgG/IgG4 dropped from 3236/665 to 706/51 mg/dl, C3/C4 went up from 49/6 to 99/27 mg/dl, and the IgG4-RD responder index fell from 10 to 1. CD20+ B cells decreased from 8.7 to 0.5%. A striking drop in interstitial plasma cell infiltrate as well as normalization of IgG4/IgG-positive plasma cells was observed at repeat biopsy. Both clinical and immunological improvement persisted over a 4-year follow-up. Treating these patients who were affected by aggressive IgG4-RD with renal involvement in an effort to induce a prolonged B cells depletion with IgG4 and cytokine production decrease resulted in a considerable rise in eGFR, with IgG4-RD RI normalization and a noteworthy improvement in clinical and histological features. Furthermore, the TIN subgroup was shown not to need for any maintenance therapy.

Lessons Learned Comparing Immune System Alterations of Bacterial Sepsis and SARS-CoV-2 Sepsis

Background

Bacterial sepsis has been used as a prototype to understand the pathogenesis of severe coronavirus disease 2019 (COVID-19). In addition, some management programs for critically ill COVID-19 patients are also based on experience with bacterial sepsis. However, some differences may exist between these two types of sepsis.

Methods

This retrospective study investigated whether there are differences in the immune system status of these two types of sepsis. A total of 64 bacterial sepsis patients and 43 patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sepsis were included in this study. Demographic data were obtained from medical records. Laboratory results within 24 h after the diagnosis of sepsis were provided by the clinical laboratory.

Results

The results of blood routine (neutrophil, lymphocyte, and monocyte counts), infection biomarkers (C-reactive protein, ferritin, and procalcitonin levels), lymphocyte subset counts (total T lymphocyte, CD4+ T cell, CD8+ T cell, B cell, and NK cell counts), and lymphocyte subset functions (the proportions of PMA/ionomycin-stimulated IFN-γ positive cells in CD4+, CD8+ T cells, and NK cells) were similar in bacterial sepsis patients and SARS-CoV-2 sepsis patients. Cytokine storm was milder, and immunoglobulin and complement protein levels were higher in SARS-CoV-2 sepsis patients.

Conclusions

There are both similarities and differences in the immune system status of bacterial sepsis and SARS-CoV-2 sepsis. Our findings do not support blocking the cytokine storm or supplementing immunoglobulins in SARS-CoV-2 sepsis, at least in the early stages of the disease. Treatments for overactivation of the complement system and lymphocyte depletion may be worth exploring further.

Impact of Long-Term Cryopreservation on Blood Immune Cell Markers in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Implications for Biomarker Discovery

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex neuroimmune disorder characterized by numerous symptoms of unknown etiology. The ME/CFS immune markers reported so far have failed to generate a clinical consensus, perhaps partly due to the limitations of biospecimen biobanking. To address this issue, we performed a comparative analysis of the impact of long-term biobanking on previously identified immune markers and also explored additional potential immune markers linked to infection in ME/CFS. A correlation analysis of marker cryostability across immune cell subsets based on flow cytometry immunophenotyping of fresh blood and frozen PBMC samples collected from individuals with ME/CFS (n = 18) and matched healthy controls (n = 18) was performed. The functionality of biobanked samples was assessed on the basis of cytokine production assay after stimulation of frozen PBMCs. T cell markers defining Treg subsets and the expression of surface glycoprotein CD56 in T cells and the frequency of the effector CD8 T cells, together with CD57 expression in NK cells, appeared unaltered by biobanking. By contrast, NK cell markers CD25 and CD69 were notably increased, and NKp46 expression markedly reduced, by long-term cryopreservation and thawing. Further exploration of Treg and NK cell subsets failed to identify significant differences between ME/CFS patients and healthy controls in terms of biobanked PBMCs. Our findings show that some of the previously identified immune markers in T and NK cell subsets become unstable after cell biobanking, thus limiting their use in further immunophenotyping studies for ME/CFS. These data are potentially relevant for future multisite intervention studies and cooperative projects for biomarker discovery using ME/CFS biobanked samples. Further studies are needed to develop novel tools for the assessment of biomarker stability in cryopreserved immune cells from people with ME/CFS.

A discrete subset of epigenetically primed human NK cells mediates antigen-specific immune responses

Adaptive features of natural killer (NK) cells have been reported in various species with different underlying mechanisms. It is unclear, however, which NK cell populations are capable of mounting antigen-specific recall responses and how such functions are regulated at the molecular level. Here, we identify and characterize a discrete population of CD49a+CD16- NK cells in the human liver that displays increased epigenetic potential to elicit memory responses and has the functional properties to exert antigen-specific immunity in the skin as an effector site. Integrated chromatin-based epigenetic and transcriptomic profiling revealed unique characteristics of hepatic CD49a+CD16- NK cells when compared with conventional CD49a-CD16+ NK cells, thereby defining active genomic regions and molecules underpinning distinct NK cell reactivity. In contrast to conventional NK cells, our results suggest that adaptive CD49a+CD16- NK cells are able to bypass the KIR receptor-ligand system upon antigen-specific stimulation. Furthermore, these cells were highly migratory toward chemokine gradients expressed in epicutaneous patch test lesions as an effector site of adaptive immune responses in the skin. These results define pathways operative in human antigen-specific adaptive NK cells and provide a roadmap for harnessing this NK cell subset for specific therapeutic or prophylactic vaccine strategies.

Innate Lymphocytes in Inflammatory Arthritis

Inflammatory arthritis (IA) refers to a group of chronic diseases, including rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS), and other spondyloarthritis (SpA). IA is characterized by autoimmune-mediated joint inflammation and is associated with inflammatory cytokine networks. Innate lymphocytes, including innate-like lymphocytes (ILLs) expressing T or B cell receptors and innate lymphoid cells (ILCs), play important roles in the initiation of host immune responses against self-antigens and rapidly produce large amounts of cytokines upon stimulation. TNF (Tumor Necrosis Factor)-α, IFN (Interferon)-γ, Th2-related cytokines (IL-4, IL-9, IL-10, and IL-13), IL-17A, IL-22, and GM-CSF are involved in IA and are secreted by ILLs and ILCs. In this review, we focus on the current knowledge of ILL and ILC phenotypes, cytokine production and functions in IA. A better understanding of the roles of ILLs and ILCs in IA initiation and development will ultimately provide insights into developing effective strategies for the clinical treatment of IA patients.

Selective modulation of trans-endothelial migration of lymphocyte subsets in multiple sclerosis patients under fingolimod treatment

Multiple sclerosis (MS) is an autoimmune disorder where auto-aggressive T cells target the central nervous system (CNS), causing demyelination. The trans-endothelial migration of leucocytes across the blood-brain barrier (BBB) is one of the earliest CNS events in MS pathogenesis. We examined the effect of the disease state and treatment with fingolimod on the transmigration of peripheral blood mononuclear cells (PBMCs) in an in vitro BBB model. Patients' leucocyte numbers, subsets and phenotypes were assessed by flow cytometry. As expected, fingolimod treatment induced a significant reduction in T cell and B cell numbers compared to untreated MS patients and healthy controls. Interestingly fingolimod led to a marked reduction of CD4+ and a significant increase in CD8⁺ cell numbers. In migrated cells, only CD3⁺ cell numbers were reduced in fingolimod-treated, compared to untreated patients; it had no effect on B cell or monocyte transmigration. T cells were then differentiated into naïve, effector and memory subsets based on their expression of CCR7. This showed that MS patients had increased numbers of effector memory CD4⁺ cells re-expressing CD45RA (TEMRA) and a decrease in central memory (CM) CD8⁺ cells. The former was corrected by fingolimod, while the latter was not. CM CD4⁺ and CD8⁺ cells migrated across BBB more efficiently in fingolimod-treated patients. We found that while fingolimod reduced the proportions of naïve CD19⁺ B cells, it significantly increased the proportions of these cells which migrated. When B cells were further stratified based on CD24, CD27 and CD38 expression, the only effect of fingolimod was an enhancement of CD24^hiCD27⁺ B cell migration, compared to untreated MS patients. The migratory capacities of CD8^hi Natural Killer (NK), CD8^dim NK and NK-T cells were also reduced by fingolimod. While the disease-modifying effects of fingolimod are currently explained by its effect on reducing circulating auto-aggressive lymphocytes, our data suggests that fingolimod may also have a direct though differential effect on the trans-endothelial migration of circulating lymphocyte populations.