Enhanced production of intracellular IL-4 in blood basophils (a) or liver basophils (b) derived from BALB/c-IL-3+/+ vs IL-3−/− mice after incubation with exogenous IgE and anti-IgE activation in vitro. On day 10 of infection, freshly isolated blood leukocytes (a) or liver cells (b) from N.b.-infected (500 larvae, subcutaneously) BALB/c-IL-3+/+ mice. Data in a are from two separate experiments, in each of which blood leukocytes were pooled from three to four mice of each genotype. Aliquots of the pooled cells (in experiment 1) or of two separate aliquots of the pooled cells (in experiment 2) were analyzed after treatment with or without exogenous IgE and with or without anti-IgE ex vivo (n=2–3 values per treatment group). Data in b are from one experiment, which analysed liver cells from four IL-3+/+ mice and from three IL-3−/− mice. Cells in a and b were incubated on ice±IgE for 50 min, followed by stimulation for 4 h at 37°C with anti-IgE mAb, the last 2 h in the presence of monensin. Basophils, identified as FcγR+, CD45+ cells, were examined for intracellular IL-4 production by FACS. The data are shown as % of basophils (mean±s.e.m.) that exhibit staining for intracellular IL-4 and MFI (mean±s.e.m.) of such IL-4+ basophils. * indicates P<0.05; **P<0.001; and ***P<0.0001 vs corresponding values for vehicle controls of the same genotype. †indicates P<0.05; ††P<0.001; †††P<0.0001 vs the values indicated by the square brackets. NS, not significant (P>0.05).