The Role of HLA Antibodies in HLA Mismatched Allogeneic Hematopoietic Stem Cell Transplantation.

Published reports suggest that engraftment failure after hematopoietic stem cell transplantation (HSCT) is closely associated with the presence of donor-specific HLA antibodies (DSA). Herein, we report a single cohort retrospective analysis of 567 cases of HLA mismatched allogeneic HSCT patients from the Lu Dao-pei Hematology Center, transplanted between September 11, 2012, and November 20, 2014. Of these cases, 306 patients underwent HLA class I and II antibody testing within one month before transplantation. For patients with HLA antibody screening resulting in an HLA antibody with a mean fluorescence intensity (MFI) > 1000, single antigen bead HLA class I and II testing was performed. Then, according to donor HLA genotype, we determined whether DSA were present. Of the 306 patients with pre-transplant HLA antibody screening (LABScreen Mixed Antigen), HLA class I antibodies were present in 51 cases (16.7%). HLA class II antibodies were present in 24 cases (7.8%). Of all antibody positive cases, 20 cases were positive for HLA antibodies on single antigen beads at an MFI > 1000. Half of these cases were DSA positive. Of the non-DSA antibody cases (n = 1 0), there was one case of primary graft failure after HSCT. In the ten DSA positive patients, the HSCT was chosen from the reactive donor. Seven of these cases were treated prior to HSCT with 1-2 times plasmapheresis or high-dose intravenous immunoglobulin (IVIG) therapy. The other three cases had no special treatment to decrease HLA antibodies before transplantation. All 10 DSA positive cases achieved successful engraftment. There was one case of primary graft failure in the group of 273 patients who were HLA antibody negative. Out of the group of 261 patients who did not undergo HLA antibody screening, there were 7 cases of primary engraftment failure. The incidence of engraftment failure was lower in the group of patients who had been screened for HLA antibodies prior to transplant than it was for the patients who had not been screened (2/306 versus 7/261, p = 0.054). Five of the 7 cases of engraftment failure were screened for HLA antibodies at 30 days after first transplantation. The results of five of the cases were negative for HLA antibodies and the patients underwent second transplants, all achieving successful engraftment. This cohort researched HLA antibodies and their effect on engraftment of HSCT in Chinese cases. We compared 306 patients who underwent HLA antibody screening and were given the appropriate treatment before HSCT if DSA were positive, with 261 patients who were not screened for HLA antibodies. We found that the incidence of primary graft failure significantly decreased. Although not directly determined, HLA antibodies (especially DSA) are the cause of engraftment failure and our findings reflect the importance of HLA antibody screening prior to transplantation. We suggest that patients with pre-existing DSA should be treated with plasma exchange or IVIG therapy before transplantation.