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

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.