HLA DQ antibodies are the commonest de novo [DN] DSA specificity seen post renal transplantation. Their presence is associated with antibody mediated injury and allograft loss. However it is known that allorecognition is epitope rather than antigen dependent and that epitopes may be shared between two or more HLA antigens.

The aim of this study is determine the significance of DQ epitope mismatching in the development of DN DQ DSA. We retrospectively identified patients transplanted at our centre who had a single DQ antigen mismatch (MM) by low resolution typing. Epitopes were determined using Tersaki defined epitopes (TerEp). DSA were detected at times of allograft dysfunction and routine screening. 50/485[10.3%] of patients mismatched [MM] at a single DQ antigen developed a DQ DSA. The median TerEp MM was higher in the DSA+ [median 4(IQR:3-6)] compared with DSA- [median 3(IQR: 2-4)] patients, p<0.0001. By ROC analysis, patients MM at ≥4 epitopes were at risk of developing a DSA. DSA free survival was 87.1% and 66.1% in patients MM at ≤3 and ≥4 epitopes respectively, p<0.001. AMR risk was also increased in the ≥4 MM group but TG and allograft loss were not significantly different between the ≤3 and ≥4 groups as shown in the table 1.

This study demonstrates that DQ epitope mismatching may predict the development of de novo DQ DSA and AMR in patients who have an equivalent mismatch by low resolution typing.

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