Inhibition of PI3K p110δ activity reduces IgE production in IL-4 and anti-CD40 stimulated human tonsil B cell cultures

Abstract

Phosphoinositide 3-kinase (PI3K) p110{delta} signalling negatively regulates the production of mouse IgE. However, there are disparities between the mouse and human IgE biology, and the role of PI3K p110{delta} in the production of human IgE is yet to be determined. To investigate the effect of PI3K p110{delta} inhibition in the production of human IgE we isolated human B cells from tonsil tissue and stimulated them with IL-4 and anti-CD40 antibody to induce class switching to IgE and IgG1 in the presence or absence of IC87114, a small molecule inhibitor of PI3K p110{delta}. Using FACS, RT-PCR and ELISA we examined the effect of PI3K p110{delta} inhibition on IgE production and also determined the mechanisms involved. Unlike in mice, we observed that PI3K p110{delta} inhibition significantly reduces the number of IgE+ switched cells and the amounts of secreted IgE in IL4 and anti-CD40 cultures. However, the number of IgG1+ cells and secreted IgG1 were largely unaffected by PI3K p110{delta} inhibition. The expression levels of AID, {varepsilon} and {gamma}1 germinal transcripts or other factors involved in the regulation of CSR to IgE and IgG1 were also unaffected by IC87114. However, we found that IC87114 significantly decreases the proliferation of tonsil B cells stimulated with IL-4 and anti-CD40, specifically reducing the frequency of cells that had undergone 4 divisions or more. Our data identifies proliferation as the key mechanism through which PI3K p110{delta} regulates CSR of human B cells to IgE and highlights PI3K p110{delta} as a pharmacological target for the treatment of allergic disease.