Serological Investigations of Trichomonads. I. Comparisons of “Natural” and Immune Antibodies

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Abstract
SYNOPSIS. Active, normal sera or other body fluids from many vertebrate species were found to cytolyze Tritrichomonas augusta; heat inactivated sera agglutinated the organisms. Techniques were devised for quantitative determination of “natural” agglutinating and lytic activity against a number of trichomonads. Amphibian, avian, mammalian, and reptilian sera all possessed activity, as did chicken egg yolk, or yolk sac contents, human ascitic fluid, and cow's milk. For individuals of a given species, levels of “natural” agglutinin did not vary significantly. Among donor species, there were wide and consistent differences. The serum of any one individual, tested against 6 strains of T. augusta, showed constant activity. Agglutinating activity was relatively unaffected by changes of physical factors in the reaction milieu. Lytic activity was restored to heat‐inactivated serum by addition of guinea pig serum as a source of complement. When serum was fractionated, agglutinating activity was found primarily in the γ globulins and on into the β. On the basis of these reactions and the activity of specific serum fractions, an antibody mechanism has been postulated.By means of reciprocal agglutination tests with absorbed sera, both “natural” and immune agglutinins have been shown to be specific for Tritrichomonas augusta, T. foetus, and T. suis (?), as well as for Trickomonas gallinarum and Trichomonas vaginalis. Absorption with one species does not remove activity against others. Among strains of T. augusta, absorption with any one removes some antibody against others, but not necessarily all. On the basis of reciprocal absorption and test of 6 strains, 3 antigenic groups have been established: 2 groups are well‐separated; the 3rd intermediate between the others and cross‐reacting with both.Lack of agglutinin absorption by 2 common enterobacteria, a yeast, and Forssman antigen (sheep erythrocytes) showed that these, at least, were not involved as sources of heterophil stimulation for “natural” antibody. Whether “natural” antibody results from heterophil stimulation, however, or is genetically determined, has not been answered. Direct stimulation of “natural” antibody production by occult infection with trichomonads could not have occurred in the case of trichomonad‐free, laboratory reared chicks, or mammalian sera active against T. augusta.