Recombination in human leukocyte antigen region in two Asian Indian families

BACKGROUND: Recombination (crossing over) may generate novel haplotypes that can be beneficial to a population against recently introduced pathogens. It may lead to the generation of new alleles. SETTINGS AND DESIGN: A prospective study at a tertiary care centre. AIM: To report two rare cases of crossing over in HLA region. MATERIALS AND METHODS: Tissue-typing was done by sequence specific primers (SSP) for DR locus and by both SSP and serology for Class I which was reconfirmed on fresh samples. RESULTS: In one patient crossing over had taken place in the region of A locus resulting in inheritance of A*01 instead of expected A*11. In second family crossing over had taken place in region of DRB1 locus and the sibling inherited DRB1*08 instead of DRB1*10. CONCLUSIONS: Possibility of recombination must be considered when interpreting implausible tissue-typing results of families worked up for BMT.