Abstract: | The presence in the organism of an inhibitory factor expressing its activity under conditions of increased macromolecular globulins production (of M-immunoglobulins in particular) was established experimentally. The inhibitory factor depressed the avidity of the macromolecular antibodies; its appearance preceded reduction of the macromolecular protein level in the blood serum. The inhibitory effect of the blood serum in blood letting and vaccination with bacterial antigen is connected with the blood serum albumins, and with increased cystein and sulfhydryl groups concentration. |