Anticipation of highly sensitised renal patients’ immunoadsorption requirements by prescreening using protein A minicolumns

Abstract

We are able to subdivide highly sensitised renal patients who wish to enter our immunoadsorption programme into two groups; those who will require acute pretransplant immunoadsorption only and those requiring regular immunoadsorption prior to transplantation. This division of patients is based on the results obtained from laboratory assessment using protein A minicolumns. Patient’s plasma is passed down a minicolumn for 6 × 10 min cycles, a sample of plasma is kept after each cycle for analysis by cell flow cytometric cross-match (FCXM). The samples are screened against cells from two normal volunteers, one expressing a previously mismatched Class I HLA antigen (MMA) to which the patient has raised persistent IgG antibodies, the other, whilst not expressing any MMAs, should express a cross-reactive HLA Class I antigen (XRA) to which the patient has formed persistent IgG antibodies. Patients are allocated into the acute pretransplant immunoadsorption group if, after 6 minicolumn cycles, the T cell FCXM vs XRA and MMA is reduced to less than 1 Log median fluorescence intensity shift above the negative control and that both these values have been reduced by at least 15% from the preimmunoadsorption figure. If these criteria are not met, regular immunoadsorption is required under cover of cyclophosphamide. Eleven patients who have been allocated by these criteria have subsequently been transplanted without any incidence of hyperacute rejection.