CD4 and systemic lupus erythematosus: The levels of TIGIT expression on CD4 + T cells increased substantially in SLE patients and had a strong correlation with disease activity [66, 67]; however, activation, proliferation, and production of cytokines were decreased [67]. It was recently reported that type 1 interferon (IFN-I) stimulates LAG-3 expression while inhibiting TIGIT expression on human naive CD4 + and CD8 + T cells [66].