Enriched basophils from birch pollen were incubated with concentrations of nBetV1 inducing from 50 to 100% of the maximal histamine release in the presence or the absence of the mentioned HumAbs. The histamine releasewas expressed as a percentage of maximal histamine release. The mean and SD of three measurements are presented. A, when tested indicidually, only BAB1 inhibits the Betv1-induced histamine release. The five HumAbs were individually preincubated, at concentrations ranging from 0.4 to 1.5mg/ml with nBetv1 before challenging exposure of the basophils of two allergic patients (M.M and J.C). B, BAB 1 preincubated at 1.5mg/ml with nBetv1 inhibits the histamine release from the basophils of the four patients tested (H.L, E.B, M.M, and J.C). C, the Betv1-induced histamine release inhibition is specific and dose-dependent. nBetv1 was preincubated with successive dilutions of an anti-IL1a HumAB X3A3 (starting from 1.3mg/ml), of BAB1 (starting from 1.5mg/ml) or of amixture of BAB2 to BAB5 (starting at 0.1mg/ml for each) and then exposed to the baophils from patient J.C.