Passive anaphylaxis in mice with gamma-G antibodies. V. Competitive effects of different immunoglobulins and inhibition of reactions with antiglobulin sera.

Mouse antisera to DNP conjugates were fractionated on agar block electrophoresis, and each fraction was tested for ability to give anaphylactic reactions in vivo in mice and guinea-pigs, and in vitro on mouse mast cells. Concentrations of IgG1 and IgG2 globulin were measured for each fraction, and the results indicate that mouse IgG1 globulin mediates both the in vivo PCA reaction in the mouse and the in vitro mast cell sensitization. PCA reactions in guinea-pigs with mouse antisera are mediated only by electrophoretic fractions containing IgG2 globulin. PCA reactions in guinea-pigs could be blocked by the addition of IgG2a myeloma containing sera to the sensitizing anti-DNP preparation, but not by addition of IgG2b or IgG1 myeloma sera. From six different IgG1 myeloma sera tested on their capacity to block PCA reactions in mice, five showed strong inhibitory activity whereas the sixth was inactive. However, also IgG2a and IgG2b myelomas were found capable of blocking PCA reactions in mice. The passive in vitro sensitization of mouse mast cells by purified mouse anti-DNP antibodies could also be blocked by the addition of specific anti-IgG2 sera. Possible interpretations of these findings are discussed.