Crossing Over in the HLA Region

Bone marrow transplants are the treatment of choice for many malignant and non-malignant diseases, such as leukemia, bone marrow aplasia and immune deficiency. In Tunisia, only allogeneic or allograft transplants are performed between a recipient and an HLA-identical donor. Such geno-identical donors are found in the siblings of patients who are candidates for BM transplants. Donors are first selected on the basis of histocompatibility class I (HLA-A and B) by serology. This is followed by PCR-SSP or PCR-SSO for HLA class II typing of the recipient and any compatible donor. Given that all the HLA typing kits we use are of low resolution, a microsatellite screening approach has been developed. HLA typing is completed by genotyping a panel of 4 microsatellites covering the entire HLA region. The study of haplotype segregation using this panel in the various family members of a candidate for OM transplantation enabled us to highlight genetic or CO recombinations in the HLA region.