Detection of immediate hypersensitivity in rabbits by direct basophil degranulation.

The direct in vitro antigen-induced degranulation of rabbit basophils based on a simplified one-step method for the staining of these cells is reported. Degranulation was assessed by counting the number of basophils before and after exposure to antigen at 37 degrees C in the presence of Ca++. The degranulation was IgE-mediated, as shown by its passive transfer to nonimmunized rabbits by IgE-containing serum; also, the reaction was dependent on the presence of Ca++ ions and normal cell metabolism. The technique allowed the detection of serum factors capable of blocking the degranulation. It provided a means for following IgE sensitization at the cellular level, which is a better index of immediate hypersensitivity than the presence of circulating specific IgE.