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HLA Associations for Autoimmune Diseases

HLA (human leukocyte antigen) associations with autoimmune diseases are classic USMLE Step 1 memorization targets in immunology and pathology. These flashcards cover the most tested HLA-disease pairings, helping you quickly recall which MHC class and allele links to conditions like ankylosing spondylitis, celiac disease, and type 1 diabetes.

Interactive Deck

5 Cards
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HLA-B27 associated diseases

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HLA-B27 (MHC class I) → seronegative spondyloarthropathies: Ankylosing spondylitis, Psoriatic arthritis, IBD arthropathy, Reactive arthritis (PAIR mnemonic).

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HLA associations in type 1 diabetes

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Type 1 DM → HLA-DR3 and HLA-DR4 (MHC class II). These alleles present islet cell antigens to autoreactive T cells, triggering β-cell destruction.

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Celiac disease HLA association

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Celiac disease → HLA-DQ2 (most common) and HLA-DQ8. These MHC class II molecules present gliadin peptides to CD4+ T cells, triggering intestinal inflammation.

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Rheumatoid arthritis HLA association

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Multiple sclerosis HLA association

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Frequently Asked Questions

What is the difference between MHC class I and class II HLA molecules?

MHC class I (HLA-A, B, C) presents intracellular peptides to CD8+ cytotoxic T cells. All nucleated cells express class I.

MHC class II (HLA-DR, DQ, DP) presents extracellular peptides to CD4+ helper T cells. Expressed on APCs (dendritic cells, macrophages, B cells).

  • Class I → CD8+ T cells
  • Class II → CD4+ T cells

Why is HLA-B27 important for USMLE Step 1?

HLA-B27 is one of the highest-yield HLA associations on Step 1. It links to the four seronegative spondyloarthropathies (PAIR mnemonic). Patients are RF-negative, distinguishing them from RA. Ankylosing spondylitis is the prototype: young male with morning back stiffness and bamboo spine on X-ray.

How many HLA associations should I memorize for Step 1?

Focus on the top 6–8 high-yield associations: HLA-B27 (PAIR), HLA-DR3/DR4 (T1DM), HLA-DQ2/DQ8 (celiac), HLA-DR4 (RA), HLA-DR2 (MS), HLA-DR3 (SLE, Graves, Sjogren). These appear repeatedly across practice exams and high-yield review resources.