PFDN1 Protein, Mouse (His)

HLA-DPB1, a pivotal player in the immune response, is instrumental in presenting peptides derived from antigens to CD4 T-cells. Operating within the endocytic route of antigen-presenting cells (APCs), HLA-DPB1's peptide binding cleft accommodates a range of 10-30 residue peptides. This MHC class II molecule is particularly involved in the exogenous antigen presentation pathway, where peptides from degraded proteins are presented on the cell surface. The complex process involves the association of three MHC class II molecules with a CD74 trimer in the endoplasmic reticulum (ER), forming a heterononamer. Upon entry into the endosomal/lysosomal system, CD74 undergoes sequential degradation, culminating in the release of a small fragment known as CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM, which stabilizes MHC class II molecules until high-affinity antigenic peptides are bound. The resultant MHC II molecule-peptide complex is then transported to the cell membrane surface for recognition. Notably, HLA-DO in B-cells and primary dendritic cells (DCs) regulate the interaction between HLA-DM and MHC class II molecules. The lysosomal microenvironment, characterized by increased acidification, plays a crucial role in regulating antigen loading into MHC II molecules, impacting proteolysis and efficient peptide loading. The heterodimeric structure of HLA-DPB1, composed of an alpha and a beta subunit, contributes to its multifaceted role in antigen presentation.