CD27/CD70 interaction augments IgE secretion by promoting the differentiation of memory B cells into plasma cells

The induction of IgE: switching in B cells requires several signals given b y cytokines and cell contact-delivered signals, sere, we investigated the r ole of CD27/CD70 interaction in B cell IgE synthesis, The addition of CD27 ligand (CD70) transfectants to B cell cultures increased the IgE synthesis synergistically in the presence of IL-4 plus anti-CD40 mAb (anti-CD40), The effect of CD70 transfectants was dose dependent and was completely blocked by anti-CD70 mAb, CD27(+) B cells had the ability to produce IgE, which wa s increased by contact with CD70 transfectants, whereas CD27(-) B cells did not produce IgE, CD27/CD70 interaction enhanced B cell proliferation in th e presence of IL-4 or IL-4 plus anti-CD40, The augmentation of B cell proli feration by CD70 transfectants was apparent in CD27f B cells, but was mild in CD27- B cells. The helper activity for IgE synthesis by the CD27/CD70 in teraction did not contribute to the enhancement of germline E transcripts, Flow cytometric and morphological analyses demonstrated that the addition o f CD70 transfectants to B cell cultures remarkably promoted differentiation into plasma cells in the presence of IL-4 and CD40 signaling. Finally, CD2 7 cross-linking resulted in the up-regulation of positive regulatory domain I-binding factor-1. Taken together, our findings indicate that signaling v ia CD27 on 15 cells induces IgE synthesis, in cooperation with IL-4 and CD4 0 signaling, by promoting the generation of plasma cells through up-regulat ion of positive regulatory domain I-binding factor-1.