Immunological responses of the toad, Xenopus laevis, to the antigens of the ciliate, Tetrahymena pyriformis.

Toads, , were immunized with the ciliate and their sera examined for specific anti- precipitating, immobilizing, agglutinating and lytic antibodies 65–75 days later. Precipitating antibodies were detected in whole antiserum by ring and Ouchterlony tests against soluble antigens of . Immobilizing, agglutinating and lytic antibodies against living ciliates were also detected in whole serum. Antibody activity was localized in the serum fraction corresponding with mammalian γ-globulin after starch block electrophoresis and this was confirmed by immunoelectrophoresis. After fractionation on Sephadex G-200 precipitating antibodies were found to correspond with γG immunoglobulins and non-precipitating antibodies with both γM and γG. These results are comparable with the situation which exists in rabbits immunized against .