Histamine release from rat mast cells by antibodies against rat basophilic leukemia cell membrane

Attempts were made to prepare antibodies against receptors for IgE. Rat basophilic leukemia (RBL) cells were saturated with IgE and solubilized in Nonidet P-40, and IgE receptor complexes were precipitated with anti-IgE. A rabbit was immunized with the precipitates and antibodies against cell membrane components were specifically purified by using RBL cells. After absorption, the antibody preparation (anti-RBL) was specific for mast cells but did not contain anti-IgE. Anti-RBL inhibited the binding of ¹²⁵I-IgE with RBL, normal rat mast cells, and solubilized receptors. Immunofluorescence staining of RBL and mast cells with anti-RBL was significantly inhibited, if their receptors had been saturated with IgE. These results indicated that anti-RBL contained antibodies against receptor molecules. Both anti-RBL and anti-IgE induced immediate skin reactions in normal rats, whereas anti-lymphocyte serum, which cross-reacts with mast cells but lacks anti-receptors, failed to induce the reaction. Infection of rats with Nippostrongylus brasiliensis, which enhanced IgE synthesis, resulted in saturation of receptors on mast cells with IgE, increased the sensitivity of their skin to anti-IgE and abolished the reactivity to anti-RBL. The results suggested strongly that anti-receptor antibodies were responsible for the skin reactions by anti-RBL. Incubation of peritoneal mast cells from inbred Hooded Lister rats with anti-RBL resulted in histamine release without changing the viability of the cells. It appears that anti-RBL induced non-cytotoxic histamine release without participation of cell-bound IgE.