IL-4 promotes RA development via cytokine–receptor interaction, Th1 and Th2 cell differentiation, Th17 cell differentiation, T-cell receptor signaling pathway, cancer pathways, and hematopoietic cell lineage; curiously, IL-4 gene expression is lower in women with RA than in men [22]. The gene discussed is IL4; the disease is rheumatoid arthritis.