RESUMO
Outcome of unrelated donor marrow transplantation is influenced by donor/recipient matching for HLA. Prior studies assessing the effect of mismatch at specific HLA loci have yielded conflicting results. Disparity for HLA-A or HLA-B antigens increases the risk of poor marrow graft outcome, but little is known about the relevance of HLA-C matching. This work aimed to evaluate the effect of HLA-C matching on hematopoietic stem cell transplant, outcome specifically on the acute graft versus host disease [aGVHD]. Seventy patients given hematopoietic stem cell transplant [HSCT] in different transplant centers with their relevant donors were included in the study, HLA class I [HLA-A, -B] and class II [DRB1, DQR1, DPB1] typing was performed using polymerase chain reaction-sequence-specific oligonucleotide probe [PCR-SSOP] and HLA-C typed by PCR-sequence specific priming [PCR-SSP] technique. The risk of aGVHD during the first three months after HSCT was estimated. Fifty two [74.3%] donor/recipient pairs were mismatched for HLA class I alleles, eighteen [34.6%] of them experienced aGVHD. While no history ofaGVHD was reported in eighteen HLA class I full matched pairs [25.7%]. Higher incidence of aGVHD was observed with isolated HLA-A mismatch [28.6%], and for isolated HLA-B and HLA-C locus mismatch, the incidence were 25% and 16.7% respectively. The incidence of aGVHD was elevated if HLA-A or HLA-B mismatch is associated with HLA-C mismatch [40% and 37.5% respectively]. Much higher incidence of aGVHD was associated with combined HLA-A-B and-C mismatch [44.4%]. The estimated odds ratio [OR] of aGVHD for total HLA-C mismatch relative to matched pairs [univariable model] was 5.0 [95% CI 1.3-19.4; P= 0.01]. The degree of HLA-C allele mismatch [one or two alleys mismatch] were significantly related to aGVHD outcome [OR, 3.9, P= 0.03; OR, 10.8; P .009 respectively]. HLA-A or HLA-B allele disparity was also associated with aGVHD. As regard the analysis of total HLA-A and -B mismatched pairs with their corresponding matched locus, they demonstrated significant adverse effect on aGVHD [OR, 2.8; P=0.04; OR 3.0; P=0.03]. It was concluded that HLA-C may function as a powerful transplantation antigen. HLA-C compatibility should be incorporated into algorithms for donor selection to improve the outcome especially in patients who have an increased risk. The presence of HLA-C mismatch with either HLA-A or HIA-B mismatch leads to a synergistic increase in cytotoxic responses and poor graft outcomes [the development of aGVHD]; however, isolated HLA-C mismatch may be acceptable with respect to T-cell mediated alloreactivity