Differential roles of human CD4+ and CD8+ regulatory T cells in controlling self-reactive immune responses

Abstract

Here we analyzed the relative contributions of CD4+ regulatory T cells expressing Forkhead box protein P3 (FOXP3) and CD8+ regulatory T cells expressing killer cell immunoglobulin-like receptors to the control of autoreactive T and B lymphocytes in human tonsil-derived immune organoids. FOXP3 and GZMB respectively encode proteins FOXP3 and granzyme B, which are critical to the suppressive functions of CD4+ and CD8+ regulatory T cells. Using CRISPR–Cas9 gene editing, we were able to achieve a reduction of ~90–95% in the expression of these genes. FOXP3 knockout in tonsil T cells led to production of antibodies against a variety of autoantigens and increased the affinity of influenza-specific antibodies. By contrast, GZMB knockout resulted in an increase in follicular helper T cells, consistent with the ablation of CD8+ regulatory T cells observed in mouse models, and a marked expansion of autoreactive CD8+ and CD4+ T cells. These findings highlight the distinct yet complementary roles of CD8+ and CD4+ regulatory T cells in regulating cellular and humoral responses to prevent autoimmunity. Here the authors use a tonsil organoid culture model system to investigate the roles of human CD4+ and CD8+ regulatory T cells in controlling self-reactive immune responses. CD4+ regulatory T cells were stronger regulators of autoreactive B cells, autoantibodies and antigen-specific antibody affinity, whereas CD8+ regulatory T cells predominantly controlled expansion of follicular helper cells and autoreactive CD4+ and CD8+ T cells.