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PREVALENCE OF MICA ANTIBODIES IN PATIENTS AWAITING KIDNEY TRANSPLANTATION.
Julia Plote, Holger-Andreas Elsner, Dr., Ute Holtkamp, Dr., Christina Bade-Doeding and Rainer Blasczyk, Prof.. Hannover Germany, Hannover Medical School, 30625, Transfusion Medicine and Dresden Germany, MMD Medical Molecular Diagnostics GmbH, 01307.

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MICA (MHC class I related chain A) encodes stress-inducible polymorphic glycoproteins, which are activating ligands for NKG2D and γδ T cell receptor bearing cells. Previous studies described their power to induce alloantibodies following solid organ transplantation, transfusion and pregnancy. In this study we have developed an ELISA for detection of anti-MICA-antibodies in patient sera using prokaryotic V5/HIS-tagged truncated MICA*008 consisting of the three extracellular domains. By purity control we found two proteins with 19 kD and 45 kD, respectively. The Peptide mass fingerprint analysis displayed next to the expected MICA*008 a N-terminal shortened MICA*008 starting at AA position 151. This shortened MICA*008 was removed by gel-chromatography to improve sensitivity. ELISA design was assembled using the purified 45 kD protein as capture protein and anti-human-IgG-HRP for detection. Rabbit-anti-MICA-antibodies were used as positive controls. In order to test patients for anti-MICA-antibodies 1,300 sera of patients on the kidney transplant waiting list were screened. The cut-off was calculated by applying 3x standard deviation from 95 sera of non reactive blood donors (99.73% of normal distribution). 5.6 % of these patients were found to have anti-MICA-antibodies. As 10 of them had rejected previous kidneys, 4 of them without having HLA antibodies, anti-MICA antibodies may play a crucial role in organ rejection, suggesting that the presence of anti-MICA antibodies should be considered in patient management strategies.