We performed monitoring of conventional donor specific antibodies (DSA) and C1q binding DSA (C1q DSA) to correlate levels with pathology findings in protocol kidney biopsies from highly sensitized patients (calculated Panel Reactive Antibody > 99) transplanted after the new kidney allocation system went into effect since Dec 4, 2014.

7 patients with a cPRA of 100% underwent kidney transplant at our center and have had DSA, C1q DSA, kidney biopsy and creatinine (Cr) monitored at 1, 3 and 6 months. All patients had negative crossmatch at transplant. 20 biopsies and 20 serum samples for DSA, C1q DSA and Cr were obtained. 2 patients were diagnosed with antibody mediated rejection and 1 with acute cellular rejection for which they were treated. Using a threshold cut off of 100 mean fluorescence intensity (MFI) for the detection of C1q DSA all patients who had evidence of C4d deposition on kidney biopsies had detectable C1qDSA. In 5 biopsies where C4d was negative but C1q DSA was positive in serum, 1 showed microscopic evidence of glomerulitis and capillaritis and 1 acute tubular injury. Using Chi-square statistics and 2X2 contingency tables we calculated the significance of the association of DSA testing with pathology findings

MFI mean fluorescence intensity; PTC peritubular capillaritis; ATI acute tubular injury

Our analysis shows that biopsy-paired C1q DSA associates better with C4d deposition and other renal pathology compared to biopsy-paired conventional DSA testing. We conclude that inclusion of C1q testing in post-transplant monitoring of highly sensitized patients may aid the timely diagnosis of antibody-mediated rejection (AMR), including the subcategory of C4d-negative AMR. At this time all patients have Cr's that are at baseline.

CITATION INFORMATION: Kuppachi S, Holanda D, Gallegos S, Field E. C1q Donor Specific Antibody Associates with Post Transplant Biopsy Findings in Highly Sensitized Kidney Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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