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

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