FOS and autoimmune disease: Thus, CTLA-4 regulates T-cell signaling, modulates T-cell activity, maintains the balance of immunity, and protects the body from autoimmune diseases by downregulating the transcription factor activity of Fos, Jun, c-Myc, AP-1, NF-AT, and NF-κB (49), from which it protects the body from autoimmune diseases (Figure 2) (64).