PGE2 Upregulates Activation-Induced Cytosine Deaminase (AID) in Human B Lymphoblasts (34.12)

Abstract

Abstract AID is expressed in mature B cells during activation and in some non-lymphoid tissues during inflammation and malignancy. Elevated COX-2 & PGE2 characterize all the above and may be involved. We here confirm that PGE2 enhances AID in activated human B2 cells (J Immunol. 178:35.4, 2007 abstract) and explore the mechanism. AID was assessed, by immunoblotting and two-color flow cytometry of CFSE-labeled cells, following activation by anti-IgM:anti-CD21:dex + IL-4 + BAFF w/wo PGE2 or agonists/antagonists of PGE2 receptors (EP1, EP2, EP3, and EP4). PGE2 added at physiological doses augmented AID. EP2 was involved on the basis of (a) AID-augmenting effects of an EP2-specific agonist and (b) concordant upregulation of AID and EP2 on replicating blasts. Furthermore, PGE2-mediated elevation of AID was thwarted by inhibitors of PKA, downstream of EP2. To examine whether autocrine PGE2 synthesis contributes to AID, replicating cells were assessed for mPGE2-1 - an enzyme that converts COX-2-generated PGH2 to PGE2. Elevated mPGE2-1 in progeny and COX-2 inhibitor-reduced AID both suggest that autocrine PGE2 promotes AID. Additionally, functional AID (on the basis of IgG+ progeny) was elevated and reduced by exogenous PGE2 and COX-2 inhibitors, respectively. Thus PGE2, elaborated by classic inflammatory cells or generated during activation, augments AID expression/function in EP2-expressing human B lymphoblasts. NIH R01 AI52189; M01 General Clinical Research Center grant RR018535; and Karches Foundation