Transcriptional switch of hepatocytes initiates macrophage recruitment and T-cell suppression in endotoxemia

BACKGROUND & AIMS

The liver plays crucial roles in the regulation of immune defense during acute systemic infections. However, the roles of liver cellular clusters and intercellular communication in the progression of endotoxemia have not been well-characterized.

METHODS

Single-cell RNA sequencing analysis was performed, and the transcriptomes of 19,795 single liver cells from healthy and endotoxic mice were profiled. The spatial and temporal changes in hepatocytes and non-parenchymal cell types were validated by multiplex immunofluorescence staining, bulk transcriptomic sequencing, or flow cytometry. Furthermore, we used an adeno-associated virus delivery system to confirm the major mechanisms mediating myeloid cell infiltration and T-cell suppression in septic murine liver.

RESULTS

We identified a proinflammatory hepatocyte (PIH) subpopulation that developed primarily from periportal hepatocytes and to a lesser extent from pericentral hepatocytes and played key immunoregulatory roles in endotoxemia. Multicellular cluster modeling of ligand-receptor interactions revealed that PIHs play a crucial role in the recruitment of macrophages via the CCL2-CCR2 interaction. Recruited macrophages (RMs) released cytokines (e.g., IL6, TNFα, and IL17) to induce the expression of inhibitory ligands, such as PD-L1, on hepatocytes. Subsequently, RM-stimulated hepatocytes led to the suppression of CD4⁺ and memory T-cell subsets partly via the PD-1/PD-L1 interaction in endotoxemia. Furthermore, sinusoidal endothelial cells expressed the highest levels of proapoptotic and inflammatory genes around the periportal zone. This pattern of gene expression facilitated increases in the number of fenestrations and infiltration of immune cells in the periportal zone.

CONCLUSIONS

Our study elucidates unanticipated aspects of the cellular and molecular effects of endotoxemia on liver cells at the single-cell level and provides a conceptual framework for the development of novel therapeutic approaches for acute infection.

LAY SUMMARY

The liver plays a crucial role in the regulation of immune defense during acute systemic infections. We identified a proinflammatory hepatocyte subpopulation and demonstrated that the interactions of this subpopulation with recruited macrophages are pivotal in the immune response during endotoxemia. These novel findings provide a conceptual framework for the discovery of rational therapeutic targets in acute infection.

Fatty Acid-Driven Polarization of Suppressive Bone Marrow-Derived Macrophages Including Metabolic and Functional Analysis

Macrophages represent not only the first line of defense against pathogens and are the main drivers of inflammation but are also involved in the initiation, immune evasion as well as metastasis of tumors. Therefore, it has been suggested that diminishing the immune regulatory function of macrophages would support the natural immune surveillance or antitumor therapies, respectively. However, the plasticity of macrophages represents an obstacle in understanding and manipulating the role of macrophages in tumor tissue or the tumor microenvironment. Here, we describe a protocol to differentiate macrophages, based on changing their metabolic environment, from bone marrow precursors to tumor-associated macrophage-like cells of an immune suppressive phenotype. Based on these protocols, the inhibitory functional phenotype of macrophages can be manipulated and therefore further analyzed as described, by interrupting metabolic pathways.

B cells from Patients with Rheumatoid Arthritis Show Conserved CD39-Mediated Regulatory Function and increased CD39 Expression After Positive Response to Therapy

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by progressive joint destruction associated with increased pro-inflammatory mediators. In inflammatory microenvironments, exogenous ATP (eATP) is hydrolyzed to adenosine, which exerts immunosuppressive effects, by the consecutive action of the ectonucleotidases CD39 and CD73. Mature B cells constitutively express both ectonucleotidases, converting these cells to potential suppressors. Here, we assessed CD39 and CD73 expression on B cells from treated or untreated patients with RA. Neither the frequency of CD73⁺CD39⁺ and CD73^-CD39⁺ B cell subsets nor the levels of CD73 and CD39 expression on B cells from untreated or treated RA patients showed significant changes in comparison to healthy controls (HC). CpG+IL-2-stimulated B cells from HC or untreated RA patients increased their CD39 expression, and suppressed CD4⁺ and CD8⁺ T cell proliferation and intracellular TNF-production. A CD39 inhibitor significantly restored proliferation and TNF-producing capacity in CD4⁺ T cells, but not in CD8⁺ T cells, from HC and untreated RA patients, indicating that B cells from untreated RA patients conserved CD39-mediated regulatory function. Good responder patients to therapy (R-RA) exhibited an increased CD39 but not CD73 expression on B cells after treatment, while most of the non-responder (NR) patients showed a reduction in ectoenzyme expression. The positive changes of CD39 expression on B cells exhibited a negative correlation with disease activity and rheumatoid factor levels. Our results suggest modulating the ectoenzymes/ADO pathway as a potential therapy target for improving the course of RA.

Pancreas-derived mesenchymal stromal cells share immune response-modulating and angiogenic potential with bone marrow mesenchymal stromal cells and can be grown to therapeutic scale under Good Manufacturing Practice conditions

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) isolated from various tissues are under investigation as cellular therapeutics in a wide range of diseases. It is appreciated that the basic biological functions of MSCs vary depending on tissue source. However, in-depth comparative analyses between MSCs isolated from different tissue sources under Good Manufacturing Practice (GMP) conditions are lacking. Human clinical-grade low-purity islet (LPI) fractions are generated as a byproduct of islet isolation for transplantation. MSC isolates were derived from LPI fractions with the aim of performing a systematic, standardized comparative analysis of these cells with clinically relevant bone marrow-derived MSCs (BM MSCs).

METHODS

MSC isolates were derived from LPI fractions and expanded in platelet lysate-supplemented medium or in commercially available xenogeneic-free medium. Doubling rate, phenotype, differentiation potential, gene expression, protein production and immunomodulatory capacity of LPIs were compared with those of BM MSCs.

RESULTS

MSCs can be readily derived in vitro from non-transplanted fractions resulting from islet cell processing (i.e., LPI MSCs). LPI MSCs grow stably in serum-free or platelet lysate-supplemented media and demonstrate in vitro self-renewal, as measured by colony-forming unit assay. LPI MSCs express patterns of chemokines and pro-regenerative factors similar to those of BM MSCs and, importantly, are equally able to attract immune cells in vitro and in vivo and suppress T-cell proliferation in vitro. Additionally, LPI MSCs can be expanded to therapeutically relevant doses at low passage under GMP conditions.

CONCLUSIONS

LPI MSCs represent an alternative source of GMP MSCs with functions comparable to BM MSCs.

Neutrophils suppress tumor-infiltrating T cells in colon cancer via matrix metalloproteinase-mediated activation of TGFβ

High T-cell infiltration in colorectal cancer (CRC) correlates with a favorable disease outcome and immunotherapy response. This, however, is only observed in a small subset of CRC patients. A better understanding of the factors influencing tumor T-cell responses in CRC could inspire novel therapeutic approaches to achieve broader immunotherapy responsiveness. Here, we investigated T cell-suppressive properties of different myeloid cell types in an inducible colon tumor mouse model. The most potent inhibitors of T-cell activity were tumor-infiltrating neutrophils. Gene expression analysis and combined in vitro and in vivo tests indicated that T-cell suppression is mediated by neutrophil-secreted metalloproteinase activation of latent TGFβ. CRC patient neutrophils similarly suppressed T cells via TGFβ in vitro, and public gene expression datasets suggested that T-cell activity is lowest in CRCs with combined neutrophil infiltration and TGFβ activation. Thus, the interaction of neutrophils with a TGFβ-rich tumor microenvironment may represent a conserved immunosuppressive mechanism in CRC.

Alkaloids from the stems and rhizomes of Sinomenium acutum from the Qinling Mountains, China

Thirteen undescribed alkaloids (sinotumines A-M), including five oxoisoaporphine, a benzo[h]quinoline, an aporphine, two protoberberine, two hasubanane, and two proaporphine alkaloids, and 50 known analogues were isolated from the 95% aqueous EtOH extract of the stems and rhizomes of Sinomenium acutum. The structures and absolute configurations of the isolates were elucidated on the basis of comprehensive analysis of 1D and 2D NMR, HRMS, single-crystal X-ray diffraction, and comparison of the experimental and calculated electronic circular dichroism (ECD) data. Sinotumine F, a rare benzo[h]quinoline alkaloid, was speculated as an oxidation product of the oxoisoaporphine alkaloid, and its putative biosynthetic pathway is proposed. Sinotumines L and M are the first samples of proaporphine-based heterodimers coupled with 1-heptanone and coniferol alcohol moiety, respectively. The T-cell suppression and NO inhibition effects of the isolates were evaluated.

Expression of checkpoint molecules on myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population expanded in cancer, infection and autoimmunity capable of suppressing T-cell functions. Checkpoint inhibitors have emerged as a key therapeutic strategy in immune-oncology. While checkpoint molecules were initially associated with T cell functions, recent evidence suggests a broader expression and function in innate myeloid cells. Previous studies provided first evidence for a potential role for checkpoints on MDSCs, yet the human relevance remained poorly understood. Therefore, we investigated the expression and functional relevance of checkpoint molecules in human MDSC-T-cell interactions. Our studies demonstrate that programmed death-ligand 1 (PD-L1) is expressed on granulocytic MDSCs upon co-culture with T cells. Transwell experiments showed that cell-to-cell contact was required for MDSC-T-cell interactions and antibody blocking studies showed that targeting PD-L1 partially impaired MDSC-mediated T-cell suppression. Collectively, these studies suggest a role for PD-L1 in human MDSC function and thereby expand the functionality of this checkpoint beyond T cells, which could pave the way for further understanding and therapeutic targeting of PD-1/PD-L1 in innate immune-mediated diseases.

Poor immune reconstitution is associated with symptomatic BK polyomavirus viruria in allogeneic stem cell transplant recipients

BACKGROUND

BK polyomavirus (BKPyV) infections are known indicators of immune suppression in hematopoietic stem cell transplant (HSCT) recipients; they can lead to hemorrhagic cystitis, ureteral stenosis, renal dysfunction, and prolonged hospital stays. In this study, we determined transplant-associated variables and immune parameters that can predict for the risk of BKPyV viruria. We hypothesized that BKPyV infection is a marker of poor immune recovery.

METHODS

We analyzed all engrafted patients undergoing first allogeneic HSCT at MD Anderson Cancer Center in Houston between January 2004 and December 2012. We evaluated their immune parameters and their transplant-associated factors. BKPyV positivity was defined as BKPyV detection in urine by polymerase chain reaction testing. Cox proportional hazards model, as well as competing risk analysis method using subdistribution hazard models with death as competing risk, were applied to assess risk of BKPyV viruria.

RESULTS

We identified a total of 2477 patients with a median age of 52 years. BKPyV viruria was manifest in 25% (n=629) of the patients. The median time from transplantation to BKPyV viruria development was 42 days among the patients who had BKPyV viruria. On multivariate analysis, tumor type, acute GVHD, chronic GVHD, myeloablative conditioning regimen, cord blood as the graft source, CD3⁺ , CD4⁺ , CD8⁺ , CD56⁺ , NK counts, and low platelet count were shown to be significantly associated with BKPyV infection. These finding were further confirmed when models incorporating the competing risk of death yielded similar findings.

CONCLUSION

In this study, we report significant associations between BKPyV reactivation following allogeneic HSCT and suppressed immune variables. In addition, this study provides valuable information on the immune status of HSCT recipients as a predictor of BKPyV infections that may in turn help us formulate plans for more effective prevention and treatment of this infection.

Differential Regulation of Myeloid-Derived Suppressor Cells by Candida Species

Myeloid-derived suppressor cells (MDSCs) are innate immune cells characterized by their ability to suppress T-cell responses. Recently, we demonstrated that the human-pathogenic fungi Candida albicans and Aspergillus fumigatus induced a distinct subset of neutrophilic MDSCs. To dissect Candida-mediated MDSC induction in more depth, we studied the relative efficacy of different pathogenic non-albicans Candida species to induce and functionally modulate neutrophilic MDSCs, including C. glabrata, C. parapsilosis, C. dubliniensis, and C. krusei. Our data demonstrate that the extent of MDSC generation is largely dependent on the Candida species with MDSCs induced by C. krusei and C. glabrata showing a higher suppressive activity compared to MDSCs induced by C. albicans. In summary, these studies show that fungal MDSC induction is differentially regulated at the species level and differentially affects effector T-cell responses.

Phenotypic and functional characteristics of CD39high human regulatory B cells (Breg)

CD39 and CD73 are key enzymes in the adenosine (ADO) pathway. ADO modulates pathophysiological responses of immune cells, including B cells. It has recently emerged that a subpopulation of ADO-producing CD39⁺CD73⁺ B cells has regulatory properties. Here, we define the CD39^high subset of these cells as the major contributor to the regulatory network operated by human B lymphocytes. Peripheral blood B cells were sorted into CD39^neg, CD39^inter and CD39^high subsets. The phenotype, proliferation and IL-10 secretion by these B cells were studied by flow cytometry. 5'-AMP and ADO levels were measured by mass spectrometry. Agonists or antagonists of A₁R, A_2AR and A₃R were used to study ADO-receptor signaling in B cells. Inhibition of effector T-cell (Teff) activation/proliferation by B cells was assessed in co-cultures. Cytokine production was measured by Luminex. Upon in vitro activation and culture of B cells, the subset of CD39^high B cells increased in frequency (p < 0.001). CD39^high B cells upregulated CD73 expression, proliferated (approximately 40% of CD39^high B cells were Ki-67⁺ and secreted fold-2 higher IL-10 and ADO levels than CD39^neg or CD39^inter B cells. CD39^high B cells co-cultured with autologous Teff suppressed T-cell activation/proliferation and secreted elevated levels of IL-6 and IL-10. The A₁R and A_2AR agonists promoted expansion and functions of CD39^high B cells. CD39 ectonucleotidase is upregulated in a subset of in vitro-activated B cells which utilize ADO and IL-10 to suppress Teff functions. Proliferation and functions of these CD39^high B cells are regulated by A₁R- and A_2AR-mediated autocrine signaling.

A reproducible immunopotency assay to measure mesenchymal stromal cell-mediated T-cell suppression

BACKGROUND AIMS

The T-cell suppressive property of bone marrow-derived mesenchymal stromal cells (MSCs) has been considered a major mode of action and basis for their utilization in a number of human clinical trials. However, there is no well-established reproducible assay to measure MSC-mediated T-cell suppression.

METHODS

At the University of Wisconsin-Madison Production Assistance for Cellular Therapy (PACT) Center, we developed an in vitro quality control T-cell suppression immunopotency assay (IPA) that uses anti-CD3 and anti-CD28 antibodies to stimulate T-cell proliferation. We measured MSC-induced suppression of CD4+ T-cell proliferation at various effector-to-target cell ratios with the use of defined peripheral blood mononuclear cells and in parallel compared with a reference standard MSC product. We calculated an IPA value for suppression of CD4+ T cells for each MSC product.

RESULTS

Eleven MSC products generated at three independent PACT centers were evaluated for cell surface phenotypic markers and T-cell suppressive properties. Flow cytometry results demonstrated typical MSC cell surface marker profiles. There was significant variability in the level of suppression of T-cell proliferation, with immunopotency assay values ranging from 27% to 88%. However, MSC suppression did not correlate with human leukocyte antigen-DR expression.

CONCLUSIONS

We have developed a reproducible immunopotency assay to measure allogeneic MSC-mediated suppression of CD4+ T cells. Additional studies may be warranted to determine how these in vitro assay results may correlate with other immunomodulatory properties of MSCs, in addition to evaluating the ability of this assay to predict in vivo efficacy.

Comparisons of phenotype and immunomodulatory capacity among rhesus bone-marrow-derived mesenchymal stem/stromal cells, multipotent adult progenitor cells, and dermal fibroblasts

BACKGROUND

Potent immunomodulatory effects have been reported for mesenchymal stem/stromal cells (MSCs), multipotent adult progenitor cells (MAPCs), and fibroblasts. However, side-by-side comparisons of these cells specifically regarding immunophenotype, gene expression, and suppression of proliferation of CD4(+) and CD8(+) lymphocyte populations have not been reported.

METHODS

We developed MAPC and MSC lines from rhesus macaque bone marrow and fibroblast cell lines from rhesus dermis and assessed phenotypes based upon differentiation potential, flow cytometric analysis of immunophenotype, and quantitative RT-PCR analysis of gene expression. Using allogeneic lymphocyte proliferation assays, we compared the in vitro immunomodulatory potency of each cell type.

RESULTS AND CONCLUSIONS

Extensive phenotypic similarities exist among each cell type, although immunosuppressive potencies are distinct. MAPCs are most potent, and fibroblasts are the least potent cell type. All three cell types demonstrated immunomodulatory capacity such that each may have potential therapeutic applications such as in organ transplantation, where reduced local immune response is desirable.

Characterization of mouse clonal mesenchymal stem cell lines established by subfractionation culturing method

AIM

To characterize single-cell-derived mouse clonal mesenchymal stem cells (mcMSCs) established with bone marrow samples from three different mouse strains.

METHODS

We established mcMSC lines using subfractionation culturing method from bone marrow samples obtained from long bones. These lines were characterized by measuring cell growth, cell surface epitopes, differentiation potential, lineage-specific gene expression and T-cell suppression capability. Nonclonal MSCs isolated by the conventional gradient centrifugation method were used as controls.

RESULTS

All mcMSC lines showed typical nonclonal MSC-like spindle shape morphology. Lines differed in optimal growth density requirement. Cell surface epitope profiles of these mcMSC lines were similar to those of nonclonal MSCs. However, some lines exhibited different expression levels in a few epitopes, such as CD44 and CD105. Differentiation assays showed that 90% of the mcMSC lines were capable of differentiating into adipogenic and/or chondrogenic lineages, but only 20% showed osteogenic lineage differentiation. T-cell suppression analysis showed that 75% of the lines exhibited T-cell suppression capability.

CONCLUSION

mcMSC lines have similar cell morphology and cell growth rate but exhibit variations in their cell surface epitopes, differentiation potential, lineage-specific gene expression and T-cell suppression capability.