Possible involvement of compliment C1q in the prozone-like phenomena found in the detection system of anti-HLA antibodies by HLA antigen-conjugated fluorescence beads

Abstract

It is well recognized that the anti-HLA antibodies in recipients are associated with prognosis of graft rejection in transplantation including both solid organ transplantation and bone marrow stem cell transplantation. Recently, a detection system for anti-HLA antibodies using the HLA-antigen-conjugated fluorescence beads has been widely used in the laboratory testing. We have experienced three cases in which a discrepancy of results between the cross-match tests and bead-based detection system for anti-HLA-antibodies. Dilution of serum with the discrepant results showed that the bead-based detection system failed to detect several specific anti-HLA-antibodies, suggesting that the discrepancy was representing the prozone-like phenomenon. Treatment of the serum with discrepant results by freeze-thaw or heat inactivation for 30 min at 56℃ suggested the involvement of complement C1q in the prozone-like phenomena. Further experiments using rabbit complement or human serum also supported the involvement of C1q in the phenomena. In addition, analysis of sequential 20 cases with anti-HLA-antibodies revealed that 10 of them showed discrepancy results and anti-HLA-antibodies were failed to be detected by using the bead-based detection system in three of them. These observations indicated the importance of considering a possibility for the prozone-like phenomena in detection of anti-HLA-antibodies.