HLA class II histocompatibility antigen, DM alpha chain is a protein that in humans is encoded by the HLA-DMA gene.
HLA-DMA belongs to the HLA class II alpha chain paralogues. HLA-DM is a heterodimer consisting of an alpha (HLA-DMA) and a beta (HLA-DMB) chain, both anchored in the membrane. It is located in intracellular vesicles. This class II molecule plays a central role in the peptide loading of MHC class II molecules by helping to release the CLIP (class II-associated invariant chain peptide) molecule from the peptide binding site. Class II molecules are expressed in antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages). The alpha chain is approximately 33-35 kDa and its gene contains 5 exons. Exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular domains, exon 4 encodes the transmembrane domain and the cytoplasmic tail.