CTLA4 and systemic lupus erythematosus: Treg cell dysfunction in SLE manifests through altered expression of co-stimulatory molecules (CTLA4, PD-1) and cytokines (IL-2, IL-10, TGF-β), impairing their immunosuppressive capacity (Bertsias et al., 2009; Tenbrock and Rauen, 2022).