Anti-HLA Antibodies in Allogeneic Hematopoietic Stem Cell Transplantation From HLA-Mismatched Unrelated Donors

Anti-HLA Antibodies (Abs) are considered an important factor in solid organ transplants and transfusion medicine, but role of humoral arm of immunological response to HLA antigens in allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unknown. Large polymorphism and immunogenicity of HLA-antigens and heterogeneity of anti-HLA Abs warrant the need of such investigation. The purpose of this study was to define presence and profiles of anti-HLA Abs detected before or after allo-HSCT from HLA-mismatched unrelated donors and their impact on allo-HSCT results.

35 HLA-mismatched donor/recipient pairs entered the study. Indication for allo-HSCT was: ALL (7pts), AML(18pts), CML(5pts), SAA(2pts), CLL(1pt), MDS(1pt) and PNH (1pt). Preparative regimen was myeloablative in 33pts (94.3%) and reduced in 2pts (5.7%). Standard GVHD prophylaxis consisted of cyclosporine, methotrexate and pre-transplant anti-thymocyte globulin (34pts) or Alemtuzumab (1pt). HLA A, B, C, DR, DQ alleles were PCR-typed. 21(60%) pts had mismatch of single HLA-antigen: A-4(11.4%), B-1(2.8%), C-13(37%), DQ-3(8,5%); 10(28.5%) pts had mismatch of single HLA-allele: A-3(8.5%), B(11.4%), DQ-3(8.5%); 4 pts had double antigenic (A+C and A+DQ) or combined antigenic/allelic (A/B and C/A) HLA mismatches. Anti-HLA A, B, C, DR, DQ, DP Abs were identified in sera collected before start of the conditioning treatment and +30 days, +100 days and 1 year after allo-HSCT with use of automated DynaChip assay utilizing microchips bearing purified class I and class II HLA antigens.

Anti-HLA Abs pre-formed before allo-HSCT were detected in 17(48.5%) pts: against class I, II or both in 6(35%), 4(24%) and 7(41%) pts. Anti-HLA Abs were detected after allo-HSCT in 25(71.4%) pts, against class I, II or both in 9(36%), 3(12%) and 13(52%) pts, respectively. In 7 pts anti-HLA Abs were not detected neither before nor after allo-HSCT. Anti-HLA Abs directed against the mismatched HLA antigens were observed in 4 pts before and in 10 pts after allo-HSCT, no anti-HLA Abs specific against mismatched alleles were detected. Allo-HSCT results obtained in studied subgroups are presented in the Table below:

Our preliminary results indicate that anti-HLA Abs are present pre- or post-transplant in mismatched allo-HSCT recipients and may be potentially responsible for the occurrence of complications, what needs to be further investigated and analyzed.

No relevant conflicts of interest to declare.