Generation of IgE B cells in‐vitro and pathway analysis by microarray reveals specific lack of NF‐kB survival pathway

IgE B cells that differentiate into plasma cells capable to secreting IgE antibodies play a central role in allergic disease. The development of a therapeutic to neutralize IgE is well documented and modulates allergic asthma. However, effective therapies that target IgE B cells specifically have not been identified. Immature murine B cells induced to undergo class switching via stimulation with IL‐4 and anti‐CD40 antibodies become either IgG1 or IgE expressing B cells, although the survival of IgE B cells is significantly reduced in‐vitro. We sought to elucidate potential mechanisms that would account for the significant cell death of IgE B cells during early development. After inducing IgG1 or IgE class switching of naïve B cells, we enriched for each B cell population and compared their gene expression profile by microarray to identify unique pathways. A total of 397 genes were differentially expressed. Among those genes, we identified the lack of a survival pathway in IgE B cells characterized by reduced mRNA expression of IKKβ, NF‐kB and cIAP, as well as BCL‐XL and BCL‐2. Furthermore, a large number of genes associated with the downstream effects of NF‐kB were specifically down regulated in IgE B cells compared to IgG1 B cells. The differential expression of this signaling pathway reflects a fundamental difference in the development of two distinct B cell subsets after identical stimulation. Source of support: Roche