Multiple Antibody Responses Following Immunization of Human Subjects with Diphtheria Toxoid

Precipitation reactions were carried out in a fluid and semi-solid medium utilizing human immune antitoxic sera unabsorbed and absorbed with P-proteins. These methods indicated that 11 of 59 Schick negative subjects hyperimmunized with diphtheria toxoid subsequently formed anti-diphtherial antibodies in addition to antitoxin. The average antitoxin titer was higher in sera showing evidence of multiple antibodies than in sera showing no evidence of multiple antibodies. The quantitative precipitation reactions of 6 of the 11 antitoxic sera were studied using preparations of crude and purified diphtheria toxin. Four immune sera exhibited quantitative characteristics of multiple antigen-antibody systems prior to absorption with P-proteins. Absorption of the sera with P-proteins caused a removal of considerable antibody nitrogen relative to antitoxin nitrogen as judged by altered quantitative behavior of absorbed sera in the presence of purified toxin. The average unit antitoxin nitrogen values before and after absorption of sera with P-proteins were as follows: unabsorbed sera 1.7 μg N/unit, absorbed sera 1.9 μg N/unit. The average in vivo/in vitro ratio was 1.02 before absorption and 1.03 following absorption.