CORRELATION OF ELISA-DETECTED IGG AND IGA ANTI-HLA ANTIBODIES IN PRETRANSPLANT SERA WITH RENAL-ALLOGRAFT REJECTION

The present study compared the occurrence of rejection episodes during the first twelve posttransplant (Tx) months and the 1-, 2-, and 3-yea r graft survivals among recipients stratified by the percent panel rea ctive antibody (% PRA) of pre-Tx sera as detected using either an anti human globulin determined PRA (AHG-% PRA) or an ELISA methodology dete cting IgG reactive against soluble HLA class I antigens (% PRA-STAT). There was a significant correlation between AHG-PRA greater than or eq ual to 10% and a PRA-STAT greater than or equal to 10% (P<0.001). Howe ver, among 200 sera displaying an AHG-PRA greater than or equal to 10% (mean 57+/-21%), only 69% (138/200) displayed a PRA-STAT greater than or equal to 10%. With further study the discrepant finding, of 62 ser a that were AHG-PRA greater than or equal to 10% but PRA-STAT <10%, wa s due to the presence of IgM and/or IgG non-MHC reactivity. In contras t, among 293 sera displaying an AHG-PRA <10% (mean 3+/-2%), 15% (43/29 3) displayed a PRA-STAT greater than or equal to 10%. There was no cor relation between AHG-% PRA and rejection episodes occurring during the first twelve post Tx months. In contrast, however, there was a highly significant correlation between PRA-STAT greater than or equal to 10% and the occurrence of rejection episodes during the first twelve post -Tx months (P<0.001). Patients with PRA-STAT greater than or equal to 10% experienced a 70% rejection frequency compared with the 35% reject ion frequency for patients with PRA-STAT sera < 10% (P<0.001). A signi ficant correlation was observed between the presence of IgG-1 and reje ction (P<0.01) but not IgG-subclasses 2, 3, or 4. Of particular intere st was the observation in 11 patients that the presence of ELISA-detec ted IgA anti-HLA class I antigen (ELISA-IgA PRA greater than or equal to 10%) was associated with a significantly reduced rejection risk com pared with sera where only PRA-STAT greater than or equal to 10% was p resent (27% vs. 70% incidence of rejection episodes, P<0.01). Finally, patients displaying pretransplant PRA-STAT results < 10% experienced significantly improved 1-, 2-, and 3- year graft survivals of 85% vs. 74%, 82% vs. 70% and 81% vs. 67%, respectively (P<0.01 for each time p oint), compared with patients displaying PRA-STAT results greater than or equal to 10%. These data suggest that the use of the ELISA methodo logy to detect IgG reactivity against soluble HLA class I antigens (PR A-STAT) may allow for the determination of a more clinically informati ve % PRA than the AHG-% PRA. Moreover, the presence of ELISA-detected IgA anti-HLA may act to inhibit rejection mechanisms associated with E LISA-detected IgG anti-HLA greater than or equal to 10%.