Figure 4.

Spontaneous dephosphorylation of receptors after stimulation with antigen. Two separate incubation mixtures were prepared in duplicate. In each at t = 0, RBL-2H3 cells (6.25 × 10⁶/ml), which had been partially sensitized with DNP-specific mouse IgE, were reacted with rat IgE oligomer (0.3 μg/ml). At t = 10 min, DNP_18.5-BSA (1 μg/ml) and 10 μg/ml monomeric rat IgE (protocol a) or monomeric dansyl-specific mouse IgE (protocol b) was added. At each time point, the cells were solubilized. The IgEs were immunoprecipitated with species-specific anti-mouse IgE (protocol a) or anti-rat IgE (protocol b). Recovery of receptors was confirmed by recovery of [¹²⁵I]-IgE dimer. The immunoprecipitated receptors were assessed for phosphotyrosine. The data are the average of two samples. (a) Time course of the phosphorylation of receptors bound to anti-DNP mouse IgE. (b) Time course of the phosphorylation of receptors bound to rat IgE oligomers. The ordinate values are graphed on a relative scale; the absolute ratio of the data in a:b approximated 7:1.