ANTIBODY-BINDING FOLLOWING EXPOSURE OF LIVE ICHTHYOPHTHIRIUS-MULTIFILIIS (CILIOPHORA) TO SERUM FROM IMMUNE CARP CYPRINUS-CARPIO

Trophont stages of the ciliate fish parasite Ichthyophthirius multifil iis were incubated alive in vitro in serum from immune carp Cyprinus c arpio and subsequently examined immunohistologically for bound antibod y. Parasites became immobilized in immune serum and were enveloped by gelatinous mucus-like material. Carp antibody could not be detected bo und to cilia membranes (the major surface antigens), although it was d etected at low levels in parasite food vacuoles and associated with th e gelatinous material. This material is probably responsible for the i mmobilization of parasites, and may form a barrier that prevents acces s of large amounts of cilia-membrane-specific antibody to the parasite surface during in vitro incubation in fish serum.