LABORATORY IMMUNOLOGY AND KIDNEY TRANSPLANTATION

K. Mizutani¹, M. Gotoh¹, P.I. Terasaki^2
1Urology, Nagoya University Graduate School of Medicine, Nagoya/JAPAN, ², Terasaki Foundation Laboratory, Los Angeles/UNITED STATES OF AMERICA

Body: Introduction Capillary C4d was an established marker of antibody-mediated rejection in kidney transplants. Recently, Wahrmann, et al. showed that C4d can be detected on flow cytometry beads after C4 was bound to anti-HLA antibodies, and C4d fixation to antibodies against HLA-coated beads is a novel way to test for complement fixing antibodies in the serum. They postulated that this assay may detect antibodies which are c, therefore revealing the antibodies which play an important role in graft rejection. Our aim in this study is to find the differences between regular HLA antibody tests and C4d-bounded antibody, and check the possibility that this assay might be useful in distinguishing complement-activating or non-complement-activating. Methods We applied this with FlowPRA and LABScreen (One Lambda,Inc., Canoga Park, CA) to sera from patients who had either failed grafts (n=101) or functioning grafts(n=108) , to check the possibility that this assay might be useful in distinguishing two types of antibodies (complement-activating or noncomplement-activating antibodies). Results In 101 Failure patient samples, 50 sera were positive in IgG anti-HLA antibodies (HLA class I: 32 positive, class II: 37 positive). In 108 Function patient samples, 11 patients were positive in IgG anti-HLA antibodies (HLA class I: 8 positive, class II: 7 positive). Compared with the Failure patients, the frequency of HLA antibody positive patients were statistically significant. (p<0.0001) We found that C4d fixing antibodies were present in the sera of patients who subsequently had graft failure (39 in 101 failure cases), but found only a few C4d fixing antibodies in the sera of patients with functioning transplants (3 in 108 function cases) (p<0.0001). In later antibody dilution studies, we noted that C4d fixation occurs only at high titers of antibodies, and fluorescence was lost as sera were diluted further. Conclusion We concluded that the peak fluorescence levels of antibodies are more important that those of C4d. The quantitative aspect of antibody testing using the peak fluorescence value appears to be a valuable factor when examining anti-HLA antibodies post-transplantation.

Disclosure: All authors have declared no conflicts of interest.