UTILITY OF MIXED LYMPHOCYTE CULTURE FOR B ONE-MARROW TRANSPLANTATION INVOLVING RELATED AND UNRELATED DONORS

With the growing development and routine use of high-resolution DNA ty ping techniques for HLA class II alleles the importance of mixed lymph ocyte cultures (MLC) with respect to bone marrow transplantation is un der controversial discussion. Therefore, results of MLC assays perform ed for donor/recipient pairs were analysed in comparison to the degree of histocompatibility as determined by prospective serological and re trospective DNA typing. Three different groups were evaluated for MLC data: (A) siblings sharing two parental haplotypes, (B) related donors sharing one haplotype, with 1-3 MM on the second haplotype, (C) pheno typically identical unrelated donors. In group A, all MLCs were negati ve. In contrast, 55 out of 59 MLCs in group B and 30 out of 41 in grou p C were positive. In group C, 11 MLCs were positive despite phenotypi c class I and DRB 1 compatibility. We conclude from our results that, at present, MLC is not mandatory for genotypically HLA-identical sibli ngs while for donor/recipient pairs of groups B and C MLC should be ca rried out even in cases of phenotypical compatibility for class I and DRB 1 alleles.