The trypanocidal action of human serum and of baboon plasma

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Abstract
Baboon plasma is 5 times as active as human serum in killing organisms such as Trypanosoma equiperdum. There are apparently 2 closely related serum substances: A which acts in vitro and B which acts in vivo. Usually there is 20-40 times as much B as A. In vitro, trypanocidal action is completed in less than 6 h. In vivo the action is a little slower. Substance A is suppressed when human serum is injected i.v. into rats and mice but B is made more active. The sbustances could not be removed from serum by adsorption with large numbers of trypanosomes. Human serum and baboon plasma were fractioned by ion-exchange chromatography and by gel filtration. The active fractions were examined by immunoelectrophoresis. The active substances are a2 macroglobulins with molecular weight about 300,000. Both substances apparently possess the same protein nucleus, but they differ slightly in configuation and/or composition. Some sera, initially inactive in vitro, yielded highly active fractions after gel filtration; this activation might be due to conversion of B into A or to removal of inhibitors masking A. When trypanosomes are exposed to serum there is a latent period of 1/2 h, after which the trypanosomes become distorted until they are almost globular. As shown by the electron microscope, there is progressive disintegration of the cytoplasm and large clear spaces appear beneath the pellicle.

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