Invariant chain–MHC class II complex (Ii–MHC II complex)

The *invariant chain–MHC class II complex* is a transient, intracellular assembly crucial for the biosynthesis and antigen-presenting function of MHC class II molecules. The invariant chain (CD74) binds to newly synthesized MHC class II α/β heterodimers in the endoplasmic reticulum, forms trimers that interact with three MHC II dimers, and blocks the peptide-binding groove to prevent premature loading of endogenous antigens[1][3][4]. This complex facilitates the proper folding of MHC II, directs its trafficking to endosomal compartments, and undergoes proteolytic degradation releasing the CLIP fragment, which is subsequently replaced by antigenic peptides before transport and display on the cell surface for recognition by CD4+ T cells[1][3][4][6]. Disruption or targeting of the invariant chain–MHC II complex has biomedical significance in modulating immune responses, treating autoimmune diseases, and cancer immunotherapy[6][4].

Other names

CD74–MHC class II complexInvariant chain–class II complexIi–MHC II complexClass II–Ii nonamerMHC class II–CLIP complex

Antibody-mediated inhibition/blockade of CD74/invariant chain leading to immune modulation, apoptosis in certain cancers, and interference with antigen presentation Immune cell depletion or modulation of antigen presentation by preventing MHC class II surface expression or function