CD40

The major histocompatibility complex (MHC) is responsible for binding peptide fragments arising from pathogens in order to display them on the cell surface for recognition from immune cells.  Once recognized, the foreign pathogen is typically evaded. The MHC complex is broken into two categories, MHC Class I proteins and MHC Class II proteins.  MHC complex I and II proteins are all very different and contain specific molecules to bind different peptides – in fact, they have been described as the most polymorphic genes there are.

MHC molecules (also known as major histocompatibility complex molecules) assist in the presentation of antigens to T cells in order to eradicate foreign pathogens.  These molecules are highly polymorphic, meaning that they exist in multiple variants in order to avoid pathogens evading their activation of the immune response.  MHC Class I molecules in particular deliver cytosolic peptides to the cell surface so that they can continue on through the cytosol and ultimately the endoplasmic reticulum (ER).

BAFF belongs to the tumor necrosis factor (TNF) family, and its downstream signaling plays a critical role in B-cell survival and maturation. BAFF overproduction is associated with a variety of autoimmune diseases. BAFF is the functional ligand for three receptors: