Effects of Bothriocephalus acheilognathi on the polarization response of pronephric leucocytes of carp, Cyprinus carpio

An in vitro assay was used to examine the effect of Bothriocephalus acheilo gnathi Yamaguti, 1934 (Cestoda: Pseudophyllidea) on the polarization respon se of pronephric leucocytes of carp, Cyprinus carpio. Leucocytes, isolated from naive, naturally-infected fish and carp injected intraperitoneally wit h cestode extracts, were exposed to parasite extracts (protein concentratio ns 0-10.0 mu g ml(-1)), for up to 24 h in the presence or absence of carp s erum. In general, polarization responses of the pronephric leucocytes, prim arily neutrophils and eosinophils, increased with incubation time although there was no significant difference in the response induced by the differen t protein concentrations. Differences in the polarization response were, ho wever, observed in naive, naturally infected and injected fish and the cell s responded differently in the presence and absence of carp serum. In the a bsence of carp serum the polarization response of pronephric leucocytes in vitro was significantly reduced with cells obtained from injected and natur ally infected fish compared with those obtained from naive carp. This suppr ession of leucocyte migration was however reduced by the addition of carp s erum to the in vitro system. The role of this interaction between the possi ble suppression of polarization induced by the parasite and stimulation by serum is discussed.