CD154 Antigen

The CD154 antigen (CD40-ligand), also known as TRAP (Tumor necrosis factor Related Activation Protein), is a member of the Tumor Necrosis Factor (TNF) superfamily. It is a 32 kDa type II transmembrane molecule. CD154 is rapidly induced on T cells (CD4+ and some CD8+ cells) following TCR activation. First identified on activated T cells, CD154 is also expressed on platelets, as well as monocytes and B cells. CD154 can also be shed from activated platelets and lymphocytes in a soluble form (sCD154). This ligand for the CD40 molecule is present on some basophils and mast cells. It has critical regulatory roles in T- and B-lymphocyte function. CD40/CD154 interaction is essential for the development of thymus-dependent humoral immune responses. Ligation of CD40 on B cells by CD154 on T cells promotes B cell proliferation, immunoglobulin (Ig) production, isotype switching and memory B-cell generation.