The role of flow cytometry-detected IgG and IgM anti-donor antibodies in cardiac allograft recipients

Background. At our transplant center, cardiac allograft recipients undergo transplantation following a negative IgG anti-human globulin (AHG) crossmat ch (XM). Flow cytometry crossmatching (FCXM) is a more sensitive XM procedu re than the AHG XM procedure, yet there is limited information regarding th e clinical relevance of FCXM to cardiac allograft outcome. Methods. FCXM was performed retrospectively using the pretransplant sera fr om 140 recipients of primary cardiac allografts who underwent transplantati on after AHG-IgG-NEG XM. The FCXM results were correlated to posttransplant rejection and patient survival. Results. All of the patients were auto-XM-NEG, Twenty-two of 140 patients ( 16%) displayed IgG(+) FCXM and had a significantly poorer 1-year survival r ate than did 57 of the FCXM-NEG recipients (68% vs. 86%, P<0.02). Moreover, 50% of the IgG(+) FCXM recipients experienced early rejections (less than or equal to 14 days postoperatively) compared with only 16% for the FCXM-NE G recipients (P<0.01). The survival rate of 92% for IgM(+) FCXM recipients (n=37) was significantly improved compared with the 86% survival rate for F CXM-NEG control recipients (P<0.05), suggesting a protective role for IgM. Consistent with this interpretation is that the 1-year survival rate of 79% for the IgG, IgM FCXM(+) recipients (n=24) was significantly better than t he 68% survival rate for the IgG(+) FCXM recipients (P<0.02). Conclusions. These data suggest that IgG(+) FCXM identifies a subset of AHG -IgG-NEG XM cardiac allograft recipients who are at risk for early rejectio ns and poor survival. In contrast, the presence of IgM may be beneficial to survival.