Moreover, CTLA-4 regulates early T cell activation in lymphoid organs, preventing excessive activation and autoimmunity.286,289 It achieves this by controlling autoreactive T cell expansion,286 regulating B-1a B cells to prevent autoimmunity,290 and controlling T cell migration in conjunction with PD-1.291 These insights emphasize the central role of CTLA-4 in maintaining immune homeostasis and avoiding autoimmunity. Here, PDCD1 is linked to Autoimmunity.