Anti-CD4 monoclonal antibody, clone YKIX302.9 [R-PE]

Objective This study was undertaken to identify characteristics of follicular regulatory T (Tfr) cells and elucidate the mechanisms by which follicular helper T (Tfh) cells convert to Tfr cells. We probed the phenotype of T helper cells in patients with systemic lupus erythematosus (SLE) and underlying transcriptional regulation using cytokine-induced STAT family factors. Methods Peripheral blood mononuclear cells from 41 patients with SLE and 26 healthy donors were used to sort out the memory Tfh cell subset, and Tfh cells were cultured under various conditions. The phenotype of T helper cells and underlying mechanisms of transcriptional regulation were probed using flow cytometry and quantitative polymerase chain reaction analyses. These analyses evaluated the expression of characteristic markers and phosphorylation of STATs. Chromatin immunoprecipitation was used to evaluate histone modifications. Results In patients with SLE, the proportion of CD4+CXCR5+FoxP3-PD-1(high) Tfh cells was increased (P < 0.01), whereas the proportion of CD4+CXCR5+CD45RA-FoxP3(high) activated Tfr cells was decreased (P < 0.05). Serum interleukin-2 (IL-2) levels were also reduced in patients with SLE. IL-2 induced conversion of memory Tfh cells to functional Tfr cells, which was characterized by CXCR5+Bcl-6+FoxP3(high) pSTAT3+pSTAT5+ cells. The loci of FOXP3 and BCL6 at STAT binding sites were marked by bivalent histone modifications. Following IL-2 stimulation, STAT3 and STAT5 selectively bound to FOXP3 and BCL6 gene loci accompanied by suppression of H3K27me3. Finally, IL-2 stimulation suppressed the generation of CD38+CD27(high) plasmablasts in Tfh and B cell coculture assays ex vivo. Conclusion Impaired function of Tfr cells might be attributed to defective IL-2 production. Exogenous IL-2 restores the function of Tfr cells through the conversion of Tfh cells to Tfr cells in patients with SLE. Thus, restoring balance between Tfh and Tfr cells may provide new therapeutic approaches in SLE.

Background. We recently reported that a novel CXCR5(+)IFN-gamma(+)CD8(+) T-cell subset significantly inhibits posttransplant alloantibody production in a murine transplant model. These findings prompted the current study to investigate the association of human CD8(+) T cells with the same phenotype with the development of de novo donor-specific antibody (DSA) after kidney transplantation. Methods. In the current studies, we prospectively and serially analyzed peripheral blood CD8(+) and CD4(+) T-cell subsets and monitored for the development of de novo DSA in kidney transplant recipients during the first-year posttransplant. We report results on 95 first-time human kidney transplant recipients with 1-year follow-up. Results. Twenty-three recipients (24.2%) developed de novo DSA within 1-year posttransplant. Recipients who developed DSA had significantly lower quantities of peripheral CXCR5(+)IFN-gamma(+)CD8(+) T cells (P = 0.01) and significantly lower ratios of CXCR5(+)IFN-gamma(+)CD8(+) T cell to combined CD4(+) Th1/Th2 cell subsets (IFN-gamma(+)CD4(+) and IL-4(+)CD4(+) cells; P = 0.0001) compared to recipients who remained DSA-negative over the first-year posttransplant. Conclusions. Our data raise the possibility that human CXCR5(+)IFN-gamma(+)CD8(+) T cells are a homolog to murine CXCR5(+)IFN-gamma(+)CD8(+) T cells (termed antibody-suppressor CD8(+) T cells) and that the quantity of CXCR5(+)IFN-gamma(+)CD8(+) T cells (or the ratio of CXCR5(+)IFN-gamma(+)CD8(+) T cells to Th1/Th2 CD4(+) T cells) may identify recipients at risk for development of DSA.