In vitro demonstration of serological cross-reactivity between Ichthyphthirius multifiliis foquet and Tetrahymena pyriformis lwoff

Abstract The antigenic relation between Tetrahymena pyriformis (Ehrenberg, 1830) Lwoff 1947 and Icthyophthirius multifiliis Fouquet 1876 was investigated using various in vitro immunologic tests. Tomites of I. multifiliis exposed to dilutions of rabbit anti-tetrahymena serum were immobilized in 24 hours. Tetrahymena in this test system were agglutinated at low dilutions and immobilized at higher dilutions. Using an indirect fluorescent antibody test, both organisms showed fluorescence when treated with either rabbit anti-tetrahymena serum or rabbit anti-tomite serum. In heterologous crosses, titers of 1:1024 were obtaibed using the passive hemagglutination test. These results indicate that an antigenic relationship does exist between these two organisms, cross-reacting antigens appear to be localized on the cilia.