Identification of a coelomic mitogenic factor in Eisenia foetida earthworm

Coelomic fluid of earthworms Eisenia foetida (Oligochaeta, Annelida) exerts a mitogenic activity on murine splenocytes. Total coelomic fluid was subje cted to size-exclusion chromatography and a semi-purified mitogenic fractio n (fraction 5) was isolated and further characterized. Both coelomic fluid and the semi-purified fraction 5 block concanavalin A (ConA)-induced spleen cell proliferation but exert a synergistic effect on LPS-triggered spleen cell proliferation. Using a polyclonal antiserum neutralizing the mitogenic activity of the semi-purified fraction 5, a 60-kDa component was identifie d and named CMF (coelomic mitogenic factor). CMF was found to bind ConA whi ch could account for its ability to inhibit ConA-induced spleen cell prolif eration. CMF is present in the coelomic fluid as a trimer of a 20-kDa prote in. N-terminal amino acid sequence of monomeric CMF reveals partial sequenc e homology with phospholipase A2 (PLA2). Moreover. CMF-enriched coelomic fl uid fraction 5 exerts phospholipase activity comparable with that of bovine pancreatic PLA2. Our results suggest that coelomic fluid of E. foetida con tains a ubiquitous PLA2-like enzyme which might be involved in immune react ions in earthworms such as anti-bacterial mechanisms. (C) 1999 Elsevier Sci ence B.V. All rights reserved.