INHIBITION OF MURINE B-CELL PROLIFERATION AND DOWN-REGULATION OF PROTEIN-KINASE-C LEVELS BY A PHOSPHORYLCHOLINE-CONTAINING FILARIAL EXCRETORY-SECRETORY PRODUCT

E-S 62, a major excretory-secretory product of the rodent filarial par asite, Acanthocheilonema viteae, inhibits the polyclonal activation (D NA synthesis) of mouse B cells by mitogenic anti-Ig antibodies. This e ffect appears to be due at least in part to the phosphorylcholine (PC) moiety of the molecule, because it can be mimicked by PC-BSA or PC-ch loride. Activation of the B cells by LPS is not influenced by the pres ence of E-S 62/PC, suggesting that they may target some aspect of sign aling via the Ag receptor. E-S 62/PC failed to inhibit surface Ig-medi ated generation of the second messenger, inositol triphosphate, indica ting that their target may not be the early biochemical events associa ted with activation. Exposure to E-S 62/PC was found to lead to a redu ction in the level of protein kinase C, an important downstream regula tory enzyme, in anti-Ig-treated cells. This protein-kinase C down-regu lation may be the biochemical mechanism underlying E-S 62/PC-mediated inhibition of surface Ig-activated B cells.