Weakening of genetic resistance. I. The effect of injection of endotoxin, Freund's complete adjuvant and alloantiserum.

A parent to F1 transplantation combination was used to study the weakening effect of endotoxin, Freund's complete adjuvant and alloantiserum on genetic resistance. The relationship between time of treatment with endotoxin, Salmonella typhosa, and Freund's complete adjuvant, and their weakening effect was assessed by use of the spleen colony technique. CFU growth studies revealed that both endotoxin and alloantiserum were capable of weakening genetic resistance in the spleen but were unable to induce weakening of the resistance in the femoral marrow cavity. These results led us to the conclusion that the agents might not have a direct effect on the effector cells of the resistance. The weakening induced by endotoxin and alloantiserum seemed to be related to a certain immunological phenomenon in the spleen. In this phenomenon macrophages are likely to play a role since a number of agents capable of weakening resistance were known for their capacity to influence the mononuclear phagocytic system.