The desensitization of rat mast cells sensitized under various conditions

Rat peritoneal and pleural mast cells in vitro sensitized with an excess of mouse IgE antibodies were tested for desensitization by preincubation with antigen in calcium-free conditions. It was found that 30 min preincubation in these conditions induced complete desensitization of pleural and peritoneal cells to subsequent action of specific antigen in calcium-containing medium. The extent of desensitization to the action of anti-rat IgE (nonspecific desensitization) depended on: the origin of the cells (pleural mast cells were more sensitive to desensitization), time of incubation of the cells with mouse IgE (longer time of sensitization resulted in higher extent of desensitization), anti-IgE dilutions used to rechallenge histamine release (higher extent of desensitization to higher dilutions of anti-IgE). The results suggest, that nonspecific desensitization occurs in mast cells with higher level of sensitization with mouse IgE. Some functional differences between pleural and peritoneal mast cells are also suggested.