Its molecular weight ranges between 240 and 274 amino acids.[30] CD40L, as a potential immune-enhancing molecule, can also be expressed on the cell surface of monocytes, B cells, natural killer cells, CD8+ cells, mast cells, and basophils.[31,32] The role of the CD40/CD40L signaling pathway is crucial in the pathogenesis of RA. This evidence concerns the gene CD40 and rheumatoid arthritis.