Human Lymphocyte Antigens (HLAs) present the Major Histocompatability Complex of human. Testing HLAs is important to indicate tissue compatibility with tissue transplantation. If the HLA antigens of the donor are not compatible with the recipient, the recipient will make antibodies to those antigens, accelerating rejection. Survival of the transplanted tissue is increased if HLA matching is good. Prior HLA sensitization causes antibodies to form in the blood of a transplant recipient and shortens the survival of red blood cells (RBCs) or platelets when transfused.
Human Lymphocyte Antigens are encoded by the HLA region in Chromosome 6 of human DNA. Chromosome 6 contains locus HLA-A, HLA-B, HLA-C, HLA-DM, HLA-DOA, HLA-DOB, HLA-DP, HLA-DQ, and HLA-DR which encode Human Lymphocyte Antigen types A, B, C, DM, DOA, DOB, DP, DQ, and DR respectively.
Because HLA antigens are genetically determined, they have been useful in paternity investigations. This is particularly helpful if the reputed father or child has an unusual HLA genotype. A common HLA genotype in either the father or child increases the likelihood that there are many potential fathers of that child.
The HLA system has also been used to assist in the diagnosis of certain other diseases, some types of Human Lymphocyte Antigens are associated with conditions which are mostly believed to be genetic disorders. For example, HLA B27 is present in 80% of patients with Reiter syndrome. When a patient presents with recurrent and multiple arthritic complaints, the presence of HLA-B27 supports the diagnosis of Reiter syndrome. HLA-B27 is found in 5% to 7% of normal patients.
This is particularly helpful if the reputed father or child has an unusual HLA genotype. A common HLA genotype in either the father or child increases the likelihood that there are many potential fathers of that child.
For this test, lymphocytes from the patient are extracted and incubated with anti–HLA-specific cytotoxic antibody. If the patient has the particular HLA antigen, a complex will be formed on the cell surface. Serum complement is then added to the mixture, which kills the lymphocytes and aids in determining the titer of the HLA antigen.
Positive for Specific HLA Antigens
- Ankylosing Spondylitis.
- Reiter Syndrome (Reiter’s Arthritis).
- Yersinia Enterocolitica Arthritis.
- Anterior Uveitis.
- Graves’ Disease.
- Celiac Disease/Gluten Enteropathy.
- Chronic Active Hepatitis.
- Multiple Sclerosis.
- Myasthenia Gravis.
- Dermatitis Herpetiformis.
- Juvenile Diabetes/Diabetes associated with Beta Cell autoantibodies.
- Rheumatoid Arthritis.