Abstract
This paper outlines research that has led to the concept of the inevitable participation of the immune system in an organism’s chemical homeostasis. This function of the immune system is tentatively named the ‘immune mechanism of the chemical homeostasis’ (IMCH). It is based on the theory of a permanent physiological synthesis of antibodies to endogenous biologically active substances. Minimal accumulation of biologically active substances as a result of the influence of different factors specifically activates the immune system in order to maintain its chemical homeostasis. The concept suggests the necessity of widening the notion of the range of the immune system’s censorial functions. The concept explains the preexistence of immunocompetent cells preadapted to biologically active substances and autoantibodies specific to them; the natural clonality of the B lymphocyte pool; the polyclonal lymphocyte activation triggered by mitogens, foreign proteins, erythrocytes, and microbes, and tolerance to drugs.