HLA-DM is primarily involved in the

HLA-DM plays a crucial role in the immune response, specifically in the presentation of antigens to CD4+ T helper cells. Its primary function is to facilitate the loading of antigenic peptides onto MHC class II molecules, particularly HLA-DR. HLA-DM acts as a catalyst that assists in the exchange of the invariant chain-derived peptide (CLIP) bound to HLA-DR with higher affinity peptide antigens. By promoting the release of CLIP and permitting the binding of appropriate antigenic peptides, HLA-DM ensures that MHC class II molecules present the right information to T cells for initiating a proper immune response. This is critical for effective adaptive immunity.

While there are other molecules involved in various aspects of T cell activation and peptide loading, the specific action of HLA-DM in facilitating antigen loading onto HLA-DR distinguishes it as a pivotal component in this aspect of immunity.