The Humoral Immune Response to BNT162b2 Vaccine Is Associated With Circulating CD19+ B Lymphocytes and the Naïve CD45RA to Memory CD45RO CD4+ T Helper Cells Ratio in Hemodialysis Patients and Kidney Transplant Recipients

BackgroundThe humoral and cellular immune responses to SARS-COV-2 vaccination remain to be elucidated in hemodialysis (HD) patients and kidney transplant recipients (KTRs), considering their baseline immunosuppressed status. The aim of our study was to assess the associations of vaccine-induced antibody responses with circulating lymphocytes sub-populations and their respective patterns of alterations in maintenance HD patients and KTRs.Materials and MethodsWe included 34 HD patients and 54 KTRs who received two doses of the mRNA-vaccine BNT162b2. Lymphocyte subpopulations were analyzed by flow cytometry before vaccination (T0), before the second vaccine dose (T1) and 2 weeks after the second dose (T2). The anti-SARS-CoV2 antibody response was assessed at T1 and at T2.Results31 HD patients (91.8%) and 16 KTRs (29.6%) became seropositive at T2. HD patients who became seropositive following the first dose displayed higher CD19+ B lymphocytes compared to their seronegative HD counterparts. A positive correlation was established between CD19+ B cells counts and antibody titers at all time-points in both groups (p < 0.001). KTRs showed higher naïve CD4+CD45RA+ T helper cells compared to HD patients at baseline and T2 whereas HD patients displayed higher memory CD45RO+ T cells compared to KTRs at T2. The naïve CD4+CD45RA to memory CD4+CD45RO+ T helper cells fraction was negatively associated with antibody production in both groups.ConclusionsOur study provides a potential conceptual framework for monitoring vaccination efficacy in HD patients and KTRs considering the correlation established between CD19+ B cells, generation of memory CD4+ T helper cells and anti SARS-CoV2 antibody response to vaccination.

T-Cell Epitopes Shared Between Immunizing HLA and Donor HLA Associate With Graft Failure After Kidney Transplantation

CD4+ T-helper cells play an important role in alloimmune reactions following transplantation by stimulating humoral as well as cellular responses, which might lead to failure of the allograft. CD4+ memory T-helper cells from a previous immunizing event can potentially be reactivated by exposure to HLA mismatches that share T-cell epitopes with the initial immunizing HLA. Consequently, reactivity of CD4+ memory T-helper cells toward T-cell epitopes that are shared between immunizing HLA and donor HLA could increase the risk of alloimmunity following transplantation, thus affecting transplant outcome. In this study, the amount of T-cell epitopes shared between immunizing and donor HLA was used as a surrogate marker to evaluate the effect of donor-reactive CD4+ memory T-helper cells on the 10-year risk of death-censored kidney graft failure in 190 donor/recipient combinations using the PIRCHE-II algorithm. The T-cell epitopes of the initial theoretical immunizing HLA and the donor HLA were estimated and the number of shared PIRCHE-II epitopes was calculated. We show that the natural logarithm-transformed PIRCHE-II overlap score, or Shared T-cell EPitopes (STEP) score, significantly associates with the 10-year risk of death-censored kidney graft failure, suggesting that the presence of pre-transplant donor-reactive CD4+ memory T-helper cells might be a strong indicator for the risk of graft failure following kidney transplantation.

Ripk3 Signaling Restricts the Development of Peripheral T Cell Lymphoma in Tet2 Deficient Mice

Inactive mutations of the Ten-eleven translocation (TET2) gene are commonly found in humans with multiple hematological malignancies including myeloproliferative neoplasm (MPN), acute myeloid leukemia, diffuse large B cell lymphoma, and peripheral T cell lymphomas (PTCL), and are frequently associated with poor prognosis and worse overall survival. TET2 mutations often occur in hematopoietic stem and progenitor cells (HSPCs) and are known to collaborate with additional mutations for full-blown malignant transformation. However, the molecular mechanism by which the disease identity is determined remains to be elucidated. Increased inflammatory cytokines are commonly detected in patients with TET2 mutations, which is associated with an increased risk of atherosclerotic cardiovascular diseases. Most Tet2 knockout (Tet2 -/-) mice develop MPN-like disease within 18 months, with only a few cases developing chronic lymphocyte leukemia-like disease at two years of age. The intestinal bacteria-induced inflammatory signaling plays a critical role in the pathogenesis of MPN-like disease in Tet2 -/- mice. Receptor-interacting protein kinase 3 (Ripk3) is a key mediator of inflammation cytokine-induced necroptosis and metabolic signaling. Compared to bone marrow (BM) cells isolated from wild-type mice, higher levels of Ripk3 activity can be detected in Tet2 -/- BM cells. To study the role of Ripk3 in Tet2 mutations associated with hematopoietic diseases, we crossed Tet2 conditional knockout (Tet2fx/fx Mx1-Cre +) mice with Ripk3 -/- mice to generate Tet2 and Ripk3 compound knockout (Tet2 -/-Ripk3 -/-) mice. Tet2 -/-Ripk3 -/- mice developed aggressive tumors by 12-15 months of age as characterized by profound hepatosplenomegaly and lymphadenopathy, with substantial lymphocytosis, neutrophilia, anemia, and thrombocytopenia. Histopathological analysis revealed an aggressive infiltration of tumor cells in the liver and spleen, and effacement of splenic follicular structures in diseased Tet2 -/-Ripk3 -/- mice. To characterize the type of malignancies, single-cell suspensions of the BM, peripheral blood (PB), and spleen from Tet2 -/-Ripk3 -/- were analyzed by flow cytometry and compared with wild-type and Tet2 -/- mice. As expected Tet2 -/- mice exhibited increased frequencies of myeloid cells in the PB, BM, and spleen. However, there was a marked expansion of CD4 + T cells in the PB, BM, and spleen of Tet2 -/-Ripk3 -/- mice. Detailed analyses of the T subsets demonstrated a marked expansion of both CD4 +PD1 +CXCR5 + follicular T helper cells (T fh) and CD4 +PD1 + peripheral T helper cells (T ph), indicating the development of a peripheral T cell lymphoma (PTCL) in the Tet2 -/-Ripk3 -/- mice. Additionally, disease characteristics including the reduced surface expression of CD3 in the tumor cells, increased levels of classical T h cytokines in the serum, as well as the presence of heterogeneous populations of cells within the tumor tissues recapitulate the pathological features of angioimmunoblastic T cell lymphoma (AITL), a subtype of PTCL. Elevated frequencies of splenic T fh and T ph cells were detected as early as 7 months of age in Tet2 -/-Ripk3 -/- mice. Such cells expressed inducible T cell costimulatory receptor (ICOS), an essential signaling mediator of the T fh development and proliferation. However, all other hematopoietic parameters including BM HSPCs and mature CD4 + T cells were comparable to wild type and single-gene Tet2 -/- mice. These results indicate that Ripk3 signaling inhibits PTCL development in Tet2 -/- mice by limiting the expansion of T fh and T ph cells. We are currently determining whether Ripk3 plays such a role by inducing necroptosis and/or restricting the differentiation of CD4 + naive T cells into peripheral T fh and T ph populations. We are also investigating whether Ripk3 signaling is inactivated in the tumor cells of human PTCL patients and whether we can treat such aggressive fatal diseases by reactivating Ripk3 signaling. Disclosures No relevant conflicts of interest to declare.

Lymphocyte subsets in the peripheral blood are disturbed in systemic sclerosis patients and can be changed by immunosuppressive medication

Systemic sclerosis (SSc) is a severe chronic disease with a broad spectrum of clinical manifestations. SSc displays disturbed lymphocyte homeostasis. Immunosuppressive medications targeting T or B cells can improve disease manifestations. SSc clinical manifestations and immunosuppressive medication in itself can cause changes in lymphocyte subsets. The aim of this study was to investigate peripheral lymphocyte homeostasis in SSc with regards to the immunosuppression and to major organ involvement. 44 SSc patients and 19 healthy donors (HD) were included. Immunophenotyping of peripheral whole blood by fluorescence-activated cell sorting was performed. Cytokine secretions of stimulated B cell cultures were measured. SSc patients without immunosuppression compared to HD displayed lower γδ T cells, lower T helper cells (CD3+/CD4+), lower transitional B cells (CD19+/CD38++/CD10+/IgD+), lower pre-switched memory B cells (CD19+/CD27+/IgD+), and lower post-switched memory B cells (CD19+/CD27+/IgD−). There was no difference in the cytokine production of whole B cell cultures between SSc and HD. Within the SSc cohort, mycophenolate intake was associated with lower T helper cells and lower NK cells (CD56+/CD3−). The described differences in peripheral lymphocyte subsets between SSc and HD generate further insight in SSc pathogenesis. Lymphocyte changes under effective immunosuppression indicate how lymphocyte homeostasis in SSc might be restored.

Integrative Analysis of Spatial Transcriptome with Single-cell Transcriptome and Single-cell Epigenome in Mouse Lungs after Immunization

Immunological memory is key to productive adaptive immunity. An unbiased, high through-put gene expression profiling of tissue-resident memory T cells residing in various anatomical location within the lung is fundamental to understand lung immunity but still lacking. In this study, using a well-established model on Klebsiella pneumoniae, we performed an integrative analysis of spatial transcriptome with single-cell RNA-seq and single-cell ATAC-seq on lung cells from mice after Immunization using the 10x Genomics Chromium and Visium platform. We employed several deconvolution algorithms and established an optimized deconvolution pipeline to accurately decipher specific cell-type composition by location. We identified and located 12 major cell types by scRNA-seq and spatial transcriptomic analysis. Integrating scATAC-seq data from the same cells processed in parallel with scRNA-seq, we found epigenomic profiles provide more robust cell type identification, especially for lineage-specific T helper cells. When combining all three data modalities, we observed a dynamic change in the location of T helper cells as well as their corresponding chemokines for chemotaxis. Furthermore, cell-cell communication analysis of spatial transcriptome provided evidence of lineage-specific T helper cells receiving designated cytokine signaling. In summary, our first-in-class study demonstrated the power of multi-omics analysis to uncover intrinsic spatial- and cell-type-dependent molecular mechanisms of lung immunity. Our data provides a rich research resource of single cell multi-omics data as a reference for understanding spatial dynamics of lung immunization.

A fungal antigenic driver for Löfgren’s syndrome sarcoidosis

Löfgren’s syndrome is an acute form of sarcoidosis that is characterized by the activation of CD4+ T helper cells. In this issue of JEM, Greaves et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20210785) identified a peptide derived from an airborne mold species that stimulates T cells of Löfgren’s syndrome patients in an HLA-DR3–restricted manner. An increased serum IgG antibody response to the full-length protein was also observed in those patients, indicating that the fungus Aspergillus nidulans might be the elusive microbial agent that drives acute sarcoidosis.