Prostaglandin E₂ promotes B lymphocyte Ig isotype switching to IgE

The mechanism by which PG of the E series (PGE) promote murine B lymphocyte IgE production was investigated. We previously reported that PGE, and other agents that increase intracellular cAMP, synergize with IL-4 and LPS to induce. IgE and IgG1 production while inhibiting IgM and IgG3 synthesis. These data suggested that PGE may promote IL-4-induced class switching, but the mechanism by which PGE increases IgE synthesis remained obscure. We report here that 1) PGE increases (up to 14-fold) the number of splenic B cells secreting IgE, even though PGE mildly inhibits proliferation. 2) PGE acts on sorted surface IgM positive B cells, consistent with PGE acting on uncommitted B cells to promote class switching to IgE. 3) PGE synergizes with IL-4 to induce germline ε transcripts, demonstrating that PGE acts at the level of transcription in cells that have not yet switched to IgE. 4) In the presence of PGE, rearranged mature V(D)J ε mRNA transcripts can be detected earlier and at higher levels than with IL-4 and LPS alone. Taken together, these data provide strong evidence that PGE synergizes with IL-4 and LPS to direct isotype switching to the ε heavy chain gene in purified B lymphocytes. PGE is a potentially important in vivo immunoregulator, particularly with regard to IgE production and the genesis of allergy. In support of this hypothesis, there are numerous clinical conditions (hyper-IgE, trauma, sepsis, Hodgkin's lymphoma, arthritis) in which overproduction of PGE is coincident with elevated IgE titers.