Analysis of putatative HLA-A homozygotes

HLA typing by molecular genotyping methods has become routine for class II typing and is now being pursued for class I typing. However, a deficiency in the DNA-based methodologies is the absence of information about cellular expression of the HLA molecule. This may be important in clinical HLA matching as we have identified two families with an HLA-A allele (A^*2402 and A^*0301 respectively) detected by DNA techniques but inherited as a serological “blank”. In an effort to determine the frequency of such HLA-blanks we have retrospectively analysed the HLA-A gene by PCR-SSO techniques from 200 serological HLA-A “homozygotes”.

In the 200 samples, 24 HLA-A heterozygotes were identified by PCR-SSO. These discrepancies were explained by: Two new alleles, A^*3004 and A^*24New were detected in this study. Another potential new allele, ??A^*7401 is under further investigation.

Overall, the study yielded no further examples of serologically “blank” HLA-A alleles and suggests that this is a relatively low frequency event. However, the results indicate that A2 subtypes and resolution of the A19 CREG are high priority targets for HLA-A genotyping.