Technical Articles

The MHC IIb molecule belongs to the non classical MHC class II subtype, and its gene localization, protein structure, and antigen presentation mechanism differ significantly from the classical MHC IIa molecule. These types of molecules (such as H2-O and H2-M in mice and HLA-DM and HLA-DO in humans) do not directly participate in the exogenous presentation of antigen peptides, but indirectly affect the activation and immune response intensity of CD4 ⁺ T cells by regulating the peptide loading, editing, and exchange processes of classical MHC-II molecules.

MHC IIa molecules are a classic subtype of the major histocompatibility complex class II, primarily expressed on the surface of specialized antigen-presenting cells such as dendritic cells and B cells. Unlike MHC-I, which is primarily responsible for endogenous antigen presentation, MHC-IIa specifically presents exogenous antigen peptides to CD4 ⁺ T helper cells to initiate and regulate adaptive immune responses.

Since the innovation of PD-1/PD-L1 inhibitors in tumor treatment, the search for innate immune regulatory targets has become a key direction to overcome the limitations of existing therapies. The CD47 signaling regulatory protein alpha (SIRP alpha, also known as SHPS1) axis is considered a potential target in the field of tumor immunity due to its regulation of the "self recognition" function of innate immune cells such as macrophages.

MFR protein (Macrophage Fusion Receptor), a transmembrane protein playing a crucial role in the immune system, exhibits significant differences in structural features and functional mechanisms between animals and plants. In animals, MFR protein (also known as SIRPα, CD172a) is composed of multiple subunits. Its extracellular segment contains immunoglobulin-like domains, while its intracellular segment contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs).