×

MHC Reference Tables

1. General Rules

Feature	MHC Class I	MHC Class II
Loci	HLA-A, HLA-B, HLA-C	HLA-DP, HLA-DQ, HLA-DR
Expression	All nucleated cells + Platelets	APCs (Dendritic, Macrophage, B-cells)
T-Cell	CD8+ Cytotoxic	CD4+ Helper
Antigen Origin	Endogenous (Intracellular/Viral)	Exogenous (Extracellular)
Mnemonic	Rule of 8: 1 x 8 = 8	Rule of 8: 2 x 4 = 8

2. Structure & Genetics

Feature	MHC Class I	MHC Class II
Chains	1 Long (α) + 1 Short (β2m)	2 Equal (α + β)
Binding Cleft	α1 + α2 domains	α1 + β1 domains
Peptide Length	8-10 amino acids	13-25 amino acids (variable)
Chromosome	α: Chr 6, β2m: Chr 15	Both: Chr 6
Genetics	Codominant / Polymorphic	Codominant / Polymorphic

3. Pathway

Step	MHC Class I	MHC Class II
Processing	Proteasome	Acidified Endosome
Transport	TAP (into RER)	Invariant Chain (blocks cleft)
Loading	In RER (with Tapasin)	In Endosome (CLIP removed)
Exchange	β2m stabilizes	HLA-DM swaps CLIP for peptide

4. Disease Associations (Mnemonics)

• A3: HA3mochromatosis
• B8: Don't B-l8, Dr. Addison, or you'll go to the Grave (Addison, MG, Graves)
• B27: PAIR (Psoriatic, Ankylosing, IBD, Reactive)
• DQ2/DQ8: I ate (8) too (2) much at Dairy Queen (Celiac)
• DR2: DRive to 2 distinct places (Multiple Sclerosis, Hay fever, SLE, Goodpasture)
• DR3: 2-3-SLE (SLE, Type 1 DM, Graves, Hashimoto)
• DR4: 4 walls in a Rheum (Rheumatoid, Type 1 DM)
• DR5: Pernicious (10 letters / 2 = 5)

×

Next Question