TOXIC EFFECTS OF NORMAL SERA AND HOMOLOGOUS ANTISERA ON THE CHICK EMBRYO

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Abstract
1. The specific objectives of the present investigation were at first two-fold: (1) to determine the antigenicity of the early chick embryo, and (2) to study the effects of homologous antisera on the chick embryo. However, because at the outset a profound toxic action of fresh normal rabbit serum was encountered, it became imperative to describe the toxic factor. 2. The toxic action of normal rabbit serum, characterized by the puckering of the blastoderm, the sinking of the embryo and its ultimate death, was removed by heating at 56° C. for 30 minutes. The toxic action was not restored by adding fresh guinea pig serum to heated rabbit serum. The toxicity was not removed by absorption in the cold with nonspecific antigen-antibody precipitates and/or chicken red blood cells. These results are interpreted as indicating that complement is neither necessary nor sufficient for the toxic action of fresh rabbit serum. The toxic heat-labile substance can also act independently of heat-stable substances which are removed by absorption with chicken red blood cells. 3. The antigenicity of the 72-hour chick embryo was demonstrated by its ability to elicit the production of precipitating antibodies in the rabbit. Heated rabbit antiserum against the 72-hour chick embryo evoked a weak but definite toxic response when placed on the homologous embryo. 4. In an attempt to decrease the probability of false negative reactions, methods were sought to increase the effectiveness of the antisera. Substances which may have been inactivated by heat were returned to the antiserum singly and in combination. 5. The toxic action of heated rabbit antiserum was partially enhanced by the addition of fresh guinea pig serum, rich in complement. 6. The toxic action of the heated rabbit antiserum was not increased by adding fresh rat serum, reported to contain large amounts of properdin, but was enhanced by a mixture of guinea pig serum and rat serum. 7. The results suggest the interaction of complement and properdin or a properdin-like factor in the action of the antiserum on the chick embryo.