Considerable evidence for the existence of a direct genetic control of the immune response has been presented during recent years. Experimental work with rodents are the main basis for this evidence. The first study on genetic variations in the antibody response was carried out by Gorer & Schütze (1938). Later Cinader (1960) published detailed considerations about the specificity and inheritance of the antibody response. In mice it has been demonstrated that a few dominant immune response (Ir) genes determine the ability to produce antibodies against certain specific antigens (McDevitt & Tyan 1968). The magnitude of the response is probably under the influence of polygenes, which are not associated with Ir genes. This theory is supported by selection for high and low antibody production in mice (Biozzi et al. 1972).