CD4 and rheumatoid arthritis: Comparison of METTL3 mRNA expression in CD4+ T cells among various autoimmune disorders relative to HCs demonstrated that, except for RA, METTL3 expression was generally decreased in SLE, pSS, and PS, further prompting the essentiality of METTL3 in CD4+ T-cell-mediated autoimmune and inflammatory responses (Fig. 1e).