Concanavalin A, a model "antigen" for the in vitro detection of cell-bound reaginic antibody in the rat.

Incubation of sensitized peritoneal or pleural cells, or isolated mast cells, taken from rats previously infected with the nematode, , but not of cells taken from parasite-free controls, with concanavalin A induces the release of histamine. The release mechanism triggered by Con A is virtually completed within 60 sec, depends on temperature, but not on the presence of complement, and is inhibited by sympathomimetic amines. It therefore shows striking similarities to the anaphylactic reaction induced by the specific allergen. The mechanism by which histamine release is triggered by Con A is discussed, considering the observations that trypsinized Con A is no longer able to induce histamine release, that the presence of high concentrations of trypsinized Con A inhibits the release of histamine by subsequently added Con A or allergen, and that certain carbohydrates inhibit the release of histamine induced by both Con A and allergen. Although some of the data suggest a similarity in the structure of the antigenic determinant in the Fab fragment of IgE and the receptor site for Con A, it seems more likely that Con A is reacting mainly by cross-linking of Fc regions of the immunoglobulin molecule.