LAUSR

Aim Testing for IgM anti-HLA antibodies is not routinely tested in the majority of the HLA laboratories, despite the harm that they might cause. We report here a case of 69 years old male with End Stage Renal Disease (ESRD) who received a kidney from deceased donor and developed de novo Donor Specific Antibody dnDSA with IgM isotype. Methods Pre-transplant, patient was flow cytometry crossmatched (FCXM) with the potential deceased donor for T and B cells. Screening for the presence of anti-HLA antibodies was performed using the LabScreen Single Antigen Beads (SAB) for IgG, IgM and C1q assay (One Lambda Thermo-Fisher). Results Pre-transplant FCXM and SAB testing were negative. After two weeks of transplant, creatinine was elevated to 467umol/L and the Kidney biopsy confirmed BANFF III rejection. SAB testing was negative for IgG isotype, on the other hand it was positive for IgM with anti-A1 and anti-DQ5 DSA. Interestingly, the C1q-assays fail to detect the IgM dnDSA!? The rejection was successfully treated with steroid, IVIG and thymoglobulin. Subsequently, the creatinine dropped down and the SAB testing became negative for HLA antibodies. Conclusions This case re-emphasize the challenge that might be caused by DSA of an IgM isotype. Furthermore, the same patient serum that was tested IgG-negative, C1q-negative was tested IgM-single antigen positive, it that means when C1q assay is negative, we cannot rule out IgM antibodies? Further testing/studies is needed to answer this question.