Modulation of fish lymphocyte proliferation by extracts and isolated proteinase inhibitors of ligula intestinalis (cestoda)

The ability of Ligula intestinalis to modulate host lymphocyte function was studied using whole extracts and isolated proteinase inhibitors from plerocercoids obtained from roach (Rutilus rutilus, L.) and gudgeon (Gobio gobio, L.). Parasite extracts from either fish species had broadly similar effects on the proliferation of naive roach lymphocytes. However, striking differences were observed between lymphocytes derived from the spleen or pronephros. Pronephric lymphocytes were stimulated to proliferate in a dose-dependent manner in the presence of parasite extracts, whereas splenic lymphocytes showed a dose-dependent suppression of mitogen induced proliferation in the presence of whole extracts and isolated proteinase inhibitors. It is suggested that the differences between the response of the two lymphocyte populations is due to differential susceptibility to parasite induced cytotoxicity.