The impact of anti-HLA antibodies on unrelated cord blood transplantations.

The majority of cord blood transplantations (CBTs) have human leukocyte antigen (HLA) disparities. We investigated the impact that patients' pretransplantation anti-HLA antibodies have on the outcome of CBTs. Testing for anti-HLA antibody and its specificity was performed retrospectively at the Japanese Red Cross Tokyo Blood Center with sensitive solid-phase antibody detection assays. Among 386 CBTs, which were first myeloablative stem cell transplantations for malignancies and used a single unit of cord blood, 89 tested positive. Among the antibody-positive group, the cord blood did not have the corresponding HLA type for the antibody in 69 cases (ab-positive), while 20 cases had specificity against the cord blood HLA (positive-vs-CB). Cumulative incidence of neutrophil recovery 60 days after transplantation was 83% (95% confidence interval [CI], 79%-87%) for the antibody-negative group (ab-negative), 73% (95% CI, 61%-82%) for ab-positive, but only 32% (95% CI, 13%-53%) for the positive-vs-CB (P < .0001, Gray test). With multivariate analysis, the ab-positive showed significantly lower neutrophil recovery than the ab-negative (relative risk [RR] = 0.69, 95% CI, 0.49-0.96, p = .027). The positive-vs-CB had significantly lower neutrophil recovery (RR = 0.23, 95% CI, 0.09-0.56, P = .001) and platelet recovery (RR = 0.31, 95% CI, 0.12-0.81, P = .017) than the ab-negative. Patients' pretransplantation anti-HLA antibodies should be tested and considered in the selection of cord blood.