Association of C1q Binding Status With De Novo HLA Antibody Clinical Features and Allograft Function in Kidney Transplantation Patients During Eight Years of Dynamic Follow-up

Abstract

C1q-binding donor-specific antibody (DSA) is detrimental to transplanted kidney function. However, the factors that affect C1q binding status are unclear. A total of 519 samples from 129 consecutive kidney transplantation patients during 8 years of dynamic follow-up were collected for HLA antibody (Ab) screening and C1q detection. Among the detected HLA Abs, the majority were class II, and the DQ subtypes composed the highest proportion. The C1q-binding Abs were all HLA-II, and the DQ subtypes had the highest rate of C1q positivity. With a cutoff mean fluorescence intensity (MFI) value of 7349, the sensitivity and specificity of detecting C1q-binding Abs from all HLA-II Abs were 84.48% and 83.56%, respectively. Additionally, C1q is more likely to be bound by DSA than non-donor-specific antibody (NDSA). Compared with free DSA/NDSA, the MFI values of C1q-binding DSA/NDSA are more closely correlated with serum creatinine levels and reflect the effect of anti-antibody-mediated rejection treatment more sensitively. HLA-II Abs (particularly DQ subtypes), high titers of Abs, and DSA are important relevant factors of C1q positivity. The MFI value of C1q-binding DSA may be a useful clinical indicator of HLA antibody-mediated graft injury before the appearance of histologically typical humoral rejection.