Clinical implications of flow cytometry crossmatch with T or B cells in living donor liver transplantation

Background: Acute allograft rejection (AR) in solid organ transplantation is generally regarded to develop through cell‐mediated immune response following activation of helper T cells. Since production of antibodies is also mediated by helper T cells, humoral immunity may play some roles in AR. Although flow cytometry crossmatch (FCXM) is reported as a useful method for the detection of antibodies against donor antigen, specific role of T‐ or B‐cell FCXM and its sensitivity for AR is controversial. Methods: T‐ and B‐cell FCXM using fresh donor peripheral lymphocytes were performed before and after blood‐type compatible living donor liver transplantation in 47 patients. IgM and IgG anti‐donor antibodies were analyzed in relation to clinical AR. Results: Positive pre‐transplant T‐cell FCXM was associated with a high incidence of positive post‐transplant T‐cell FCXM (p=0.017). Four of five cases (80%) with positive pre‐transplant T‐cell FCXM experienced earlier AR (day 8.0±4.4, mean±SD) than 16 of 42 cases (31%) with negative pre‐transplant T‐cell FCXM (17.3±6.8; p=0.016). In addition, higher dose of steroids was given to treat AR episodes in cases with positive pre‐transplant T‐cell FCXM (79.9±10.3 mg/kg/month) than in those with negative pre‐transplant T‐cell FCXM (47.1±26.6; p=0.039). In the first month after transplantation, 13 episodes of positive post‐transplant T‐cell FCXM were all concomitant with or preceded clinical AR compared with seven ARs in T‐cell FCXM‐negative cases (p