HLA (human leukocyte antigen) is a marker of an individual’s immune identity and tissue compatibility. HLA types are used for organ and stem‑cell transplant matching, and they can indicate susceptibility or protection for certain autoimmune diseases and infections. Specific HLA variants also predict risk for some drug hypersensitivity reactions and are used in disease‑association and diagnostic testing.

HLA typing determines a person’s human leukocyte antigen profile to match tissue for organ and stem‑cell (bone marrow) transplants, minimizing rejection. It also helps diagnose or assess risk for certain autoimmune conditions, guides drug‑hypersensitivity testing (e.g., abacavir, carbamazepine), and supports paternity/forensic investigations. Results inform donor selection, immunosuppression planning, and personalized treatment decisions.

HLA‑A and HLA‑B are human leukocyte antigen (HLA) genes encoding MHC class I proteins expressed on nearly all nucleated cells. They present intracellular peptide fragments to CD8+ T cells, enabling recognition and elimination of infected or abnormal cells. Both loci are highly polymorphic, affecting immune responses, susceptibility to some diseases, and organ transplant compatibility and rejection risk.

The three main HLA typing methods are: 1) Serological typing — antibody-based assays (complement-dependent cytotoxicity or flow cytometry) giving low-to-intermediate resolution; 2) PCR-based molecular typing — techniques like PCR-SSP or PCR-SSO providing intermediate resolution; 3) Sequence-based typing — Sanger or next-generation sequencing offering high-resolution, allele-level identification for transplantation and research. Clinically, choice depends on required resolution and clinical purpose.

HLA typing can identify genetic risk markers associated with certain autoimmune diseases (for example, HLA‑B27 with ankylosing spondylitis, HLA‑DR and HLA‑DQ variants with rheumatoid arthritis and celiac disease). However, it cannot predict disease with certainty — many carriers never develop illness and non‑HLA factors (environment, other genes) are important. HLA testing is a useful diagnostic or risk‑assessment tool, not definitive screening.

Ankylosing spondylitis is a chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints, causing persistent back pain, stiffness and reduced spinal mobility; over time vertebrae can fuse. It commonly begins in early adulthood and is linked to the HLA‑B27 gene. Symptoms may include enthesitis, uveitis and fatigue. Treatment focuses on exercise, pain control, physical therapy and medications including NSAIDs and biologics.