Peanut OIT-Induced IgG Suppresses Ex Vivo Activation Of Allergic Donor Basophils Via a Combination Of Antigen Interception and Receptor-Bound Inhibition

Abstract

RationaleWe previously reported that plasma from subjects on peanut oral immunotherapy (PNOIT) suppresses ex vivo basophil activation in peanut-allergic subjects. We investigated the identity of the suppressive plasma factor and its mechanism of action.MethodsPlasma was removed from whole blood from peanut-allergic subjects and replaced with pooled plasma from PNOIT subjects (n=10). Plasma from 0 and 12 months on PNOIT was used unaltered, diluted, or diluted and depleted of IgG. After incubation, samples were stimulated with peanut and assessed for %CD63+ basophils. In some samples, 12 month plasma was added, then removed and replaced with the original allergic plasma (“double replacement”, n=5) to assess the bound versus soluble fraction of IgG responsible for suppression of basophil activation.ResultsThe pooled plasma samples from 12 months on PNOIT decreased basophil activation when compared with pooled plasma from 0 months on PNOIT (p<0.01). IgG-depleted samples from 0 and 12 months did not show significantly different activation. Depletion of IgG in the 12 month plasma also increased activation compared with undepleted 12 month plasma (p<0.01). In addition, samples receiving diluted 12 month plasma had higher activation than their undiluted counterparts (p<0.05), a finding not observed for 0 month plasma. Sample size for double replacement limited statistical analyses, but the results followed the same pattern: “double replaced” samples had lower activation than 0 month samples, and activation equal to or higher than 12 month samples.ConclusionsPNOIT-induced IgG suppresses ex vivo activation of allergic donor basophils in a combination of antigen interception and cellular receptor binding. RationaleWe previously reported that plasma from subjects on peanut oral immunotherapy (PNOIT) suppresses ex vivo basophil activation in peanut-allergic subjects. We investigated the identity of the suppressive plasma factor and its mechanism of action. We previously reported that plasma from subjects on peanut oral immunotherapy (PNOIT) suppresses ex vivo basophil activation in peanut-allergic subjects. We investigated the identity of the suppressive plasma factor and its mechanism of action. MethodsPlasma was removed from whole blood from peanut-allergic subjects and replaced with pooled plasma from PNOIT subjects (n=10). Plasma from 0 and 12 months on PNOIT was used unaltered, diluted, or diluted and depleted of IgG. After incubation, samples were stimulated with peanut and assessed for %CD63+ basophils. In some samples, 12 month plasma was added, then removed and replaced with the original allergic plasma (“double replacement”, n=5) to assess the bound versus soluble fraction of IgG responsible for suppression of basophil activation. Plasma was removed from whole blood from peanut-allergic subjects and replaced with pooled plasma from PNOIT subjects (n=10). Plasma from 0 and 12 months on PNOIT was used unaltered, diluted, or diluted and depleted of IgG. After incubation, samples were stimulated with peanut and assessed for %CD63+ basophils. In some samples, 12 month plasma was added, then removed and replaced with the original allergic plasma (“double replacement”, n=5) to assess the bound versus soluble fraction of IgG responsible for suppression of basophil activation. ResultsThe pooled plasma samples from 12 months on PNOIT decreased basophil activation when compared with pooled plasma from 0 months on PNOIT (p<0.01). IgG-depleted samples from 0 and 12 months did not show significantly different activation. Depletion of IgG in the 12 month plasma also increased activation compared with undepleted 12 month plasma (p<0.01). In addition, samples receiving diluted 12 month plasma had higher activation than their undiluted counterparts (p<0.05), a finding not observed for 0 month plasma. Sample size for double replacement limited statistical analyses, but the results followed the same pattern: “double replaced” samples had lower activation than 0 month samples, and activation equal to or higher than 12 month samples. The pooled plasma samples from 12 months on PNOIT decreased basophil activation when compared with pooled plasma from 0 months on PNOIT (p<0.01). IgG-depleted samples from 0 and 12 months did not show significantly different activation. Depletion of IgG in the 12 month plasma also increased activation compared with undepleted 12 month plasma (p<0.01). In addition, samples receiving diluted 12 month plasma had higher activation than their undiluted counterparts (p<0.05), a finding not observed for 0 month plasma. Sample size for double replacement limited statistical analyses, but the results followed the same pattern: “double replaced” samples had lower activation than 0 month samples, and activation equal to or higher than 12 month samples. ConclusionsPNOIT-induced IgG suppresses ex vivo activation of allergic donor basophils in a combination of antigen interception and cellular receptor binding. PNOIT-induced IgG suppresses ex vivo activation of allergic donor basophils in a combination of antigen interception and cellular receptor binding.