ANTI-THY-1 ANTIBODY PROVOKES REVERSE PASSIVE CUTANEOUS ANAPHYLAXIS-LIKE REACTIONS

Antibodies to rat Thy-1, and also to murine Thy-1, could provoke rever se passive cutaneous anaphylaxis-like (RPCA-like) reactions. The thres hold amount of purified anti-Thy-1 antibodies for RPCA-like reactions was 12.5 mu g/ml. No RPCA-like reactions were obtained with IgG1 F(ab' )(2) anti-Thy-1. Cross-linking the murine anti-rat Thy-1 F(ab')(2) fra gments with goat antibody against murine F(ab')(2) anti-rat Thy-1 perm itted us to obtain RPCA-like reactions with as little as 1.5 mu g/ml. However, when the cross-linking was done with the F(ab')(2) of the sam e goat antibody, no RPCA-like reactions were obtained. The antibody ag ainst rat Fc epsilon RI alpha or its F(ab')(2) product were equally ef fective in producing RPCA-like reactions; the threshold was obtained w ith 1.5 mu g/ml. The mechanism of the difference is discussed.