The Role of Pre-existing Anti-HLA Antibodies in Severe Aplastic Anemia Patients Undergoing Allogenic Hematopoietic Stem Cell Transplantation

The objective is to underscore the significance of pre-existing anti-HLA Abs in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for SAA. A retrospective analysis was conducted using data from 244 SAA patients who underwent allo-HSCT between January 2016 and October 2022. The patient cohort was divided into two groups based on the presence of pre-existing anti-HLA Abs. Out of 244 SAA patients, 82 were tested positive for anti-HLA Abs. 17 patients were tested with DSA in haplo-HSCT. We found that the presence of pre-existing anti-HLA Abs did not influence neutrophil engraftment (P=0.600); however, it resulted in delayed platelet recovery (P=0.006). Comparatively, patients with anti-HLA Abs demonstrated lower overall survival (OS) compared to their counter parts without anti-HLA Abs (P=0.001), with a correspondingly elevated transplant-related mortality (TRM) in the former group (P=0.002). Multivariate analysis established pre-existing anti-HLA Abs as an independent risk factor for impaired platelet recovery (HR 1.67, 95% CI 1.16-2.44, P=0.006) and OS (HR 2.19, 95%CI 1.03-4.67, P=0.043). However, there were no differences between DSA and non-DSA patients after desensitization in haplo-HSCT. In summary, the presence of pre-existing anti-HLA Abs in SAA patients undergoing allo-HSCT appears to detrimentally affect platelet recovery and overall prognosis.