MHC Class I Antigen Processing and Presentation Antibody Sampler Kit #36064

The predominant function of class I MHC/β2-microglobulin dimers, which are expressed on the surface of most nucleated cell types, is to modulate the adaptive immune response by presenting proteolytic peptide fragments from cytosolic proteins to cytotoxic CD8+ T cells. In order for self and nonself peptides to be presented by MHC class I molecules, the peptide fragments must first be derived from polyubiquitinated proteins that undergo degradation via the ubiquitin-proteasome system. In the context of inflammatory processes, the enzymatic core of the proteasome can be shaped by IFNγ signaling to contain subunits, such as PSMB8/LMP7, which enhance the presentation of antigenic peptides by antigen presenting cells (1). The resulting cytosolic peptide fragments generated through ubiquitin-dependent proteasomal degradation are then transported into the ER lumen via the peptide transporters, TAP1 and TAP2, where the activity of multiple chaperone proteins, such as calnexin and calreticulin, facilitate loading onto class I MHC/β2-microglobulin dimers for transport to the Golgi and eventually, the cell surface (2-6). Defects in the expression of multiple components of the class I antigen presenting machinery have been observed in both solid and liquid tumors, which serves as a mechanism of tumor-immune evasion (7).