CD79A and rheumatoid arthritis: Besides the mentioned TNF ligands (CD40L, BAFF, and APRIL) and cytokines (TGFβ), other studies have showed additional environmental factors, like retinoic acid (RA) and other interleukins (e.g., IL-5, IL-6, IL-21), to be synergistically required for IgA synthesis [27,46].