Studies on tetanus antitoxins. II. Demonstration of at least four antitoxins of different specificity in antitoxic sera.

In this paper the antigenic structure of tetanus toxin is described. It was shown that the toxin as well as the toxoid is carrying at least four antigenic determinants. In addition to antigen-[2] already described in a previous paper, two new degraded antigens could be isolated: antigen-[1] by preparative polyacrylamide gel electrophoresis of spontaneously degraded toxin, and antigen-[3] by pH treatment of toxin. All degraded antigens are immunogenic and nontoxic. The presence of a fourth antigenic determinant on tetanus toxin could be demonstrated only after successive absorption of rabbit antitoxic serum with the antigens-[1], -[2] and -[3]. Toxin-neutralizing antibodies remained in the absorbed serum which reacted only with tetanus toxin and tetanus toxoid. Antibodies against the four antigenic determinants are present in antitoxic serum from rabbits and horses. Human antiserum, however, contained antibodies to these determinants, anti-1 antibodies being absent. All four antitoxins could neutralize tetanus toxin in vivo.