Anaphylactic hyposensitization of rat mast cells in vitro by antigen.

Anaphylactic hyposensitization of rat mast cells in vitro was demonstrated by preincubating the cells with specific antigen in suboptimal concentrations. The reduction of the histamine release was more pronounced when the cells were pre-incubated with increasing concentrations of antigen than with the final concentration. The inhibition remained unchanged for more than 3 hr. Non-specific antigen did not influence the histamine release, whereas a 70% inhibition was demonstrated by specific antigen. In rats sensitized to two different antigens, preincubation with one of these inhibited the subsequent histamine release induced by either of the two antigens. The hyposensitization could not be ascribed to blocking antibodies.