Characterization of Null Alleles of the Human Leukocyte Antigens(HLA) Complex

Overview

The widespread application of DNA techniques in medicine and biology has allowed the typing of human leukocyteantigens (HLA) at the molecular level. Comparative studies between serological and molecular biology methodshave shown the existence of null alleles, which code HLA antigens with low or no cell surface expression. Nullalleles are not detectable by standard serological typing methods and may be overlooked /or incorrectly assigned byavailable DNA methods. Although null alleles are infrequent in human populations, they should not be ignored.Errors in typing of null alleles may cause complications in the evaluation of HLA matching of donor / recipient pairsthat were originally considered HLA-compatible. The detection of null alleles and their frequency in variouspopulations requires typing of a large number of individuals by both serological andDNA-basedmethods. Knowledgeof the haplotype(s) associated with null alleles may be helpful for their identification. For this purpose, it is necessaryto perform family studies.

Key words:
histocompatibility antigens, null alleles, polymorphism, transplantation.