Disparity of IgE binding between normal and tumor mouse mast cells

The binding constants of rat and mouse IgE to normal and neoplastic rat and mouse mast cells have been measured. None of the cells distinguishes between rat and mouse IgE. Rat normal and neoplastic mast cells and mouse mastocytoma cells show very similar binding properties: k1 approximately 10(5), k-1 approximately 10(-5) and, therefore, KA approximately 10(10). Normal mouse mast cells also show a forward rate constant, k1, of 10(5) but the dissociation rate constant, k-1, is 50 times higher (5 X 10(-4)). The detergent-solubilized receptors reflect the properties of the cell-bound receptors. The discrepancy in binding by normal and neoplastic mouse mast cells remains unexplained but appears to be a reproducible finding for the cells from three strains of normal mice and three different mastocytomas studied.