HLA & Immunogenetics Frequently Asked Questions
- What is HLA?
- What does “class I” or “class II” in the test name signify?
- What do the numbers between parentheses represent in my report?
- What does the (-) in my report mean?
- For Celiac Disease, do you test for the DQ (alpha and beta) heterodimer?
Q. What is HLA?
A. HLA stands for Human Leukocyte Antigen. It is the name given to the Major Histocompatibility Complex (MHC) of man. The HLA complex of genes on human chromosome 6 encodes proteins that are centrally involved in the actions of the immune system.
Q. What does “class I” or “class II” in the test name signify?
A. The Class I region of the HLA complex includes, among other genes, HLA-A, -B, and -C. These loci code for the heavy chain of the MHC class I molecules expressed on most cells.
The Class II region includes, among other genes, the HLA-DRA1, -DQA1 and -DPA1genes, which code for the alpha chains of the DR, DQ and DP molecules. HLA-DRB1, -DQB1 and -DPB1 code for the beta chain of the DR, DQ and DP molecules. In addition to HLA-DRB1, which codes for the primary HLA specificities such as DR1, DR2, DR4, etc., other DRB genes code for the beta chain of the specificities DR52 (DRB3), DR53 (DRB4), and DR51 (DRB5), not present in all haplotypes.
Q. What do the numbers between parentheses represent in my report?
A. The number located between parentheses indicates the serological equivalent. The following tables (HLA Dictionary) include the serological equivalents used by our Immunogenetics Department when reporting results obtained for low/intermediate resolution HLA genotyping.
Q. What does the (-) in my report mean?
A. The (-) indicates that only one HLA variant was detected; therefore, there is a high probability that the patient is homozygous.
Q. For Celiac Disease, do you test for the DQ (alpha and beta) heterodimer?
A. Yes, we test for the DQA1 and DQB1 genes that code for the alpha and beta subunits of the DQ locus. An example of these results can be found on the sample report for HLA Typing for Celiac Disease.