Ligula intestinalis(L.) (Cestoda: Pseudophyllidea): polarization of cyprinid leucocytes as an indicator of host-and parasite-derived chemoattractants

Abstract

SUMMARYFreshly isolated pronephric leucocytes from roach,Rutilus rutilusand gudgeon,Gobio gobiowere exposed to extracts of plerocercoids ofLigula intestinalisfrom these two cyprinid fish. Addition of the extracts or an increase in incubation temperature from 10 to 20 °C induced polarization of neutrophils and L1 granulocytes. Cells were transformed from their typical spherical shape to elongate forms possessing a ruffled leading edge. Extracts obtained from gudgeon-Ligulastimulated polarization of both roach and gudgeon leucocytes at 10 and 20 °C. In contrast, extracts from roach-Ligula, whilst having little effect at 10 °C, suppressed temperature-induced polarization of leucocytes at 20 °C. Addition of serum to all the essays enhanced polarization and abolished the roach-Ligula-induced suppression. It is suggested that leucocyte chemoattractants are present inLigulafrom roach and gudgeon and only parasites from the former host contain an inhibitor of polarization. In addition, host-derived factors possibly complement, may be involved in leucocyte chemoattraction.