A novel strategy for the detection and definition of HLA-specific antibodies in patients awaiting renal transplantation.

Conventional testing for HLA-specific antibodies employs complement-dependent cytotoxicity (CDC) which is labour intensive and dependent on a supply of viable lymphocytes. Our strategy to minimise CDC screening is initially to screen sera by ELISA (Quikscreen) to detect HLA Class I-specific antibodies. Negative sera are then screened by flow cytometry (FCS) using lymphoblastoid cell line pools to detect HLA Class II-specific antibodies. Only Quikscreen- or FCS-positive sera are then tested by CDC and, when indicated, with an ELISA kit (PRA-STAT) for specificity definition. Of 3680 sera, 886 (24.1%) were Quikscreen positive. Of the 2794 Quikscreen-negative sera, 374 (13.4%) were FCS positive. Therefore, only 1265 of the 3680 (34.3%) sera contained HLA-specific antibodies requiring specificity definition. This novel screening strategy has significantly reduced the CDC workload of the laboratory whilst enabling the detection of additional HLA-specific antibodies.

The association between a positive T and B cell flow cytometry crossmatch and renal transplant failure.

Between January 1989 and June 1991 329 consecutive cadaveric renal transplants were carried out at this centre and, of those, 36 (10.9%) have failed. In order to assess whether the use of flow cytometry crossmatching (FCXM) would have predicted these failures, we carried out a retrospective T and B cell FCXM study comparing the failure group with a control group of 30 recipients carefully selected from patients transplanted during the same period. The number of first and second transplants in the control and failure groups was 25,5 and 23,8 respectively with six of the controls and three of the failures having panel reactive lymphocytotoxic antibodies > 50%. Stored donor material was available for 31 of the 36 failures. Two colour FCXM was performed using R-phycoerythrin-conjugated antihuman CD3 and antihuman CD19 to identify T and B cells respectively. For each recipient, three pretransplant and one post-transplant sera were tested against lymphocytes from the recipient's kidney donor. A fluorescein isothiocyanate conjugated F(ab')2 rabbit antihuman IgG was used to detect recipient IgG alloantibodies bound to donor T and/or B cells. There were no T or B cell FCXM positive (+) results in the control group whereas 11 of the 31 (35%) failures overall and nine of the 23 (39%) who failed within three months were T and B cell FCXM+ pretransplant (p = 0.0002). Seven of the nine FCXM+ results in the early failure group were with historic sera and two with historic and current sera.(ABSTRACT TRUNCATED AT 250 WORDS)