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.