MHC Class I Vs MHC Class II: Definition, 15 Differences, Examples

MHC Class I Vs. Class II Differences (MHC I Vs. MHC II)

MHC Class I Vs MHC Class II
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MHC Class I Vs MHC Class II

S.N. Characteristics MHC-I Molecule MHC-II Molecule
1 Distribution Present on almost all nucleated cells including platelets. Have a restricted tissue distribution and are mainly found on macrophages, dendritic cells, B cells, and other antigen-presenting cells.
2 Encoding genes MHC class I proteins are encoded by the HLA-A, HLA-B, and HLA-C genes. The genes encode MHC Class II proteins reside in the HLA-D region.
3 Nature of the antigen presented Antigens presented by MHC class I molecules are of endogenous origin. Antigens presented by MHC class II molecules are derived from extracellular proteins.
4 Antigen Cytosolic proteins; are sample peptides generated within the cell or those that may enter cytosol from phagosomes. Class II molecules sample peptides outside the cell such as lysosomal proteins mostly internalized from the extracellular environment.
5 Enzymes involved in peptide generation Cytosolic proteasome Endosomal and lysosomal proteases
6 Peptide loading of MHC Endoplasmic reticulum Specialized vesicular compartment
7 Peptide-loading complex Includes the ER transporter associated with antigen processing (TAP1/2), tapasin, the oxidoreductase ERp57, and the chaperone protein calreticulin. Chaperones in ER; invariant chain in ER, Golgi and MHC Class II compartment/Class II vesicle
8 Recognizing co-receptor They are recognized by CD8 co-receptors through the MHC Class I 2 subunit. They are recognized by CD4 co-receptors through 1 and 2 subunits.
9 Receptor T cell Present antigens to CD8+T cells. Present antigens to CD4+T cells.
10 Structure MHC class I molecules consist of one membrane-spanning chain produced by MHC genes and one chain produced by the 2-microglobulin gene. MHC class II molecules consist of two membrane-spanning chains, which are produced by MHC genes.
11 Building amino acids Possess 8-10 amino acids. Possess 13-18 amino acids.
12 Peptide binding domains 1 and 2 are peptide-binding domains. 1 and 1 are peptide-binding domains.
13 Invariant chain Has no invariant chain. Has an invariant chain.
14 Functional effect The presence of abundant antigens target cell for destruction. The presences of foreign antigens induce antibody production.
15 Detection Method Serology Serology and mixed lymphocyte reaction


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