Precipitating and Nonprecipitating Antibodies in the Primary and Secondary Immune Responses

Abstract

Summary The formation of antibodies to soluble protein antigens for many months after primary immunization has been confirmed. These antibodies were produced after the immunization of rabbits with bovine serum albumin, egg albumin, human γ-globulin, pig γ-globulin and bovine γ-globulin. The antibodies present in the circulation 11 to 16 days after the initial immunization could be detected by using antigen-coated red cells and, in most cases, by the precipitin technique as well. Those antibodies present in the circulation several months later could be detected only by the hemagglutination technique. The hemagglutinating antibody titer remained constant for at least 6 months after primary immunization. In some cases the nonprecipitating antibody concentration was found to rise at a time when the precipitating antibody level was declining. Hemagglutinating antibody titers of sera, following secondary immunization, rose to high levels very rapidly and then started to decline, rapidly at first and more slowly later. Only those antisera which were obtained during the early period of antibody production and which contained precipitating antibody could passively sensitize guinea pigs. Cortisone acetate inhibited the primary response to intravenously injected antigens in six out of seven rabbits. It failed, however, to inhibit the secondary antibody response.