CTLA4 and Autoimmunity: Upon encountering their cognate antigen presented by antigen-presenting cells, T cells undergo activation and proliferation.260 Early immune checkpoint molecules such as CTLA-4 are upregulated following T cell activation to maintain immune homeostasis and prevent autoimmunity by limiting the duration and intensity of the immune response.265–267 At this stage, costimulatory signals (e.g., CD28-CD80/86) and inhibitory signals (e.g., CTLA-4) are balanced to regulate T cell activation and prevent excessive immune responses.