Experimental restoration of immune response by collodial carbon during antigenic competition.

Antigenic competition which is a phenomenon in which the immune response to one antigen was suppressed by the response to a second unrelated antigen and was studied using the pair of sheep red blood cells (SRBC) and human red blood cells (HRBC) as antigens. Rats were immunized with 0.2 ml of 20 percent SRBC intravenously following the same route of the same amount of HRBC. Control rats received only 0.2 ml of 20 percent SRBC. Humoral immune response was determined by measuring the total haemagglutinating serum 2-mercaptoethanol sensitive and 2-mercaptoethanol resistant (IgG) antibodies after the various treatments by microtitre technique. The results show that immune response to the second antigen was suppressed as a result of a response to the first unrelated antigen. However, when colloidal carbon was injected two hours before the administration of the second antigen, immune response to the latter was restored, thereby eliminating antigenic competition in the system under study. It is suggested that the restoration of immune response by colloidal carbon may be due to its blockading effect on the phagocytic cells. This may be of practical importance with respect to polyvalent vaccines and immunization schedule.