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Human Leukocyte Antigen and its Role in Disease Associations
The Human Leukocyte Antigen (HLA) system is central to immune recognition. 🧬 It is a group of genes on chromosome 6 that encode proteins regulating self vs non-self recognition. HLA molecules guide T-cell responses, determine transplant compatibility, and influence autoimmune & infectious disease risk.
📑 HLA Classifications
- Class I HLA (A, B, C): Present on nearly all nucleated cells. Present endogenous peptides (e.g. viral) to cytotoxic CD8+ T cells.
- Class II HLA (DR, DP, DQ): Found on antigen-presenting cells (APCs). Present extracellular peptides to CD4+ helper T cells.
- Class III HLA: Encode complement proteins & cytokines, involved in immune regulation rather than antigen presentation.
🛡️ Role of HLA in the Immune System
- 🧩 Antigen Presentation: HLA molecules display peptides to T cells.
- 💉 Tissue Compatibility: Mismatched HLA → graft rejection. Matching is crucial in organ & bone marrow transplantation.
- ⚖️ Immune Regulation: Helps discriminate self vs non-self, preventing autoimmunity.
⚡ HLA Associations with Disease
🔴 Autoimmune Diseases
- HLA-B27 → Ankylosing spondylitis, reactive arthritis 🦴
- HLA-DR3 → Type 1 Diabetes 🍬, SLE 🦋
- HLA-DR4 → Rheumatoid arthritis 🤲
- HLA-DRB1 → Rheumatoid arthritis, multiple sclerosis 🧠
- HLA-DQ2/DQ8 → Celiac disease 🌾
- HLA-DRB1*1501 → Multiple sclerosis 🧠
🦠 Infectious Diseases
- HLA-B53 → Protection against severe malaria 🦟
- HLA-B35 → Poor prognosis in HIV 🧫
💊 Drug Hypersensitivity
- HLA-B*5701 → Abacavir hypersensitivity reaction 🚫
✅ Conclusion
HLA = the immune system’s identity badge. It directs antigen presentation, determines transplant compatibility, and underlies many autoimmune & infectious conditions. Understanding HLA is vital in autoimmunity, pharmacogenomics, and clinical transplantation. 🚑
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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