As the demand for donors for bone marrow ranplantation increases, the use of HLA-matched, gently unrelated donors represents a promising strategy. It is well documented that the clinical outcome of bone marrow transplantation is directly dependent on optimal matching for HLA class I and clss H specificities. Molecular studies have revealed the existence of a much larger number of HLA class II alleles than was antipated, many of which cannot be recognized by routine serolgical typing. Bone marrow transplantation (BMT) represents a major therapeutic option in the treatment of patients with leukemia and bone marrow failure syndromes (1). Unfortunately, 60-70% ofthese patients lack an HLA-matched related donor (2). Clinical studies have demonstrated the feasibility of using partially mismatched family members or partially or fully matched unrelated volunteers as marrow donors (3-8). Although the availability of unrelated donors is potentially very large, one important limitation is the accuracy of HLA matching of such donors, in particular for the large number of allelic differences that remain undetected by standard serological typing (9). Indeed, clinical experience with patients receiving a marrow graft from unrelated donors or haplo-identical family donors has shown that graft failure and acute graft-versus-host disease increase as the extent of HLA mismatch increases (5-8).The cloning and sequencing of HLA class II genes have revealed an unsuspected degree of diversity of HLA class II molecules. This approach has established in particular that polymorphism at several class II loci (i.e., DRBJ, DRB3, DQBJ, DQAJ, and DPBI) is much greater than was identified from current HLA class II typing by serology (9). A large number of allelic subtypes thus represent "hidden alleles," undetectable by conventional methods. Fortunately, the availability of cloned HLA class II genes makes it possible to analyze the polymorphism directly at the level of DNA (genotyping). We first proposed such an analysis based on restriction fragment length polymorphism (RFLP) (10). More recently we have presented another approach to genotyping, based on the direct recognition of allelic sequences by hybridization with locus-and allelespecific synthetic oligonucleotides ("HLA oligotyping") (11) and have shown that class II micropolymorphism can be accurately analyzed down to single amino acid differences. This HLA oligotyping procedure can now be simplified by the use of DNA previously amplified by the polymerase chain reaction (PCR) (12, 13).Based on the availability of DNA sequence information for all known alleles of DRB, DQB, and DPB loci, we have developed conditions allowing the identification of all DRBI, DRB3, DRBS, DQBJ, and DPBJ alleles in heterozygous individuals with an appropriate choice of informative sequence-specific oligonucleotides (14-18). Our oligotyping system involves two successive steps. In step 1 (HLA-DR generic typing), a battery of 14 sequence-specific probes is used to identify all major DR specificities (DR...

No abstract

No abstract

No abstract

No abstract