Abstract Text: Two regulatory T cells (Tregs) have emerged over the last several decades and proved their importance in maintaining immune response to foreign antigens and self-tolerance. One is the well-known CD4+ Treg, which depends on the transcription factor, FOXP3. The second has only become clear in the last few years, CD8+ Treg, which is closely associated with the response to infectious diseases. However, the distinct and complementary roles of these two Tregs in regulating autoantibody responses and maintaining self-tolerance are poorly understood in humans. Here we analyzed how these two Tregs controlled cellular and humoral response to common autoantigens in our recently developed human tonsil organoid system using cell depletion and CRISPR/Cas9 genes knock-out. Knocking out FOXP3 in tonsillar T cells disrupted CD4+ Tregs functions and allowed autoantigen-specific B cells to expand and mature into antibody-secreting plasma cells in the organoids. In contrast, after disrupting CD8+ Treg functions by knocking out GZMB, the organoids had only a modest effect on autoantibody production but allowed autoreactive CD4+ and CD8+ T cells to expand. In addition, CD8+ Tregs regulated plasmablasts expansion required CD4+ T cell help. These results not only reveal essential aspects of how these two T cell types operate in different aspects of autoimmune response but also show that we can mimic critical features of autoimmunity in an entirely human, in vitro system.
