Antigen-, anti-F(ab')2- and anti-IgE-induced histamine release from rat mast cells.

The existence of IgE antibody molecules on peritoneal mast cells from rats immunized with dinitrophenylated ascaris extract was demonstrated by double antibody immunofluorescence staining and by histamine release induced by anti-IgE antibodies. Cross-linking of the IgE molecules, which are fixed to mast cells, by interaction with either the homologous antigen or with antibodies to the Fab or Fc regions of IgE, triggered in the presence of calcium ions a chain of intracellular reactions which involve cyclic nucleotide modulation and energy-requiring processes leading ultimately to the release of histamine from the granules of these cells. Although there was no apparent difference in the mechanism(s) underlying the reactions triggered by any of these three agents, the extent of histamine release caused by antibodies to the Fc region of the IgE was significantly lower than that induced by cross-linking of IgE molecules through their Fab regions by reactions with either anti-Fab antibodies or antigens.