CD4 and rheumatoid arthritis: LCN2, as a potential immune regulatory molecule, induces immune tolerance by upregulating the expression of human leukocyte antigen G (HLA‐G) on CD4+ T cells and the expansion of Tregs in healthy donors, leading to autoimmune diseases (Type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis and psoriasis).88