Differences in immunoglobulin subclasses between dye exclusion and 51Cr release complement-dependent lymphocytotoxicity assays

Paradoxical differences previously noted between lymphocytotoxicity detected by dye exclusion at room temperature (CDCE) or by 51Cr release (CDC51Cr) at 37 degrees C in maternal antipaternal complement-dependent lymphocytotoxicity have suggested that CDCE and CDC51Cr at 37 degrees C, but not at 20 degrees C, may detect different immunological antibody-antigen interactions. Reactions in the two test systems against the same target cells were compared in sera from known immune dialysis patients, secondary aborting women, and refractory platelet recipients before and after heat treatment of sera, absorption with solid-phase heparin, anti-light-chain augmentation, and the addition of murine monoclonal anti-IgG subclass antibodies. The results demonstrate significant differences between the two tests using the same target and sera. Further, the results imply the presence of an inhibitor and an inhibitor of inhibitor in sera. The involvement of different immunoglobulin subclasses was shown in the two tests. These data demonstrate the necessity for further study of the nature of the differences in the mechanisms of these clinically important antibody-detecting systems.