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) crossmatch (XM). Flow cytometry crossmatching (FCXM) is a more sensitive XM procedure than the AHG XM procedure, yet there is limited information regarding the clinical relevance of FCXM to cardiac allograft outcome.

METHODS: FCXM was performed retrospectively using the pretransplant sera from 140 recipients of primary cardiac allografts who underwent transplantation 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 rate than did 57 of the FCXM-NEG recipients (68% vs. 86%, P<0.02). Moreover, 50% of the IgG(+) FCXM recipients experienced early rejections (< or =14 days postoperatively) compared with only 16% for the FCXM-NEG 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 FCXM-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 the 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 rejections and poor survival. In contrast, the presence of IgM may be beneficial to survival.