Immunological and biological identification of tumour necrosis-like factor in sponges: Endotoxin that mediates necrosis formation in xenografts

Xenografts of the sponge Geodia cydonium in its closely related species G. rovinjensis resulted in a rapid rejection of the graft within a period of 5 days. We identified an immunoreactive tumour necrosis factor (TNF)-like activity in the xenograft (M_r of 30 000) two days after grafting. In-vivo injection of 5 μg human recombinant TNF-α induced cytotoxicity in sponge cells in the same pattern and time course as during natural xenograft rejection. Anti-TNF-α polyclonals were found to react with xenograft extracts, by Western blot analysis, as from day 2 after grafting. Using ELISA we detected the TNF-like activity from day 2 after grafting with peak levels at days 4 and 5, where the amount was 0.72 ng/μg tissue DNA. By day 1, gp27 (inhibitory aggregation factor) is already formed in the xenograft. In-vitro experiments on isolated G. cydonium cells showed that addition of purified gp27 induced the production of the TNF-like activity (up to 13.5 ng/ml). Evidence is presented that gp27 is a product of the gp180 lectin receptor. We conclude that gp27 induces TNF-like factor production, resulting in destruction and dissolution of the xenograft after 5 days.