Enhanced immunologic sensitization of mice by the simultaneous injection of antigen and specific antiserum. 3. The role of antigen in controlling the immune response elicited with immune complexes.

Summary 1 )The purpose of the present study was to determine the role of antigen in controlling the immune response. 2 )Mice injected with an antigen-antibody combination in slight antigen excess were reinjected with antibody at different times. The amount of antibody injected was adjusted to leave the animal devoid of both antigen and antibody. The removal of excess antigen reduced the immune response as measured on the 8th day. The degree of suppression was inversely related to the length of time between the injections. 3 )Mice injected with an antigen-antibody combination at equivalence did not respond. If the mice were reinjected with antigen, an immune response was detected on the 8th day. The magnitude of the immune response thus obtained is proportional to the amount of antigen used in the second injection. 4 )These results demonstrate that the initial immune response can be divided into two steps. The first step involves the establishment of the immune response without antibody synthesis and this step is initiated by the complexed antigen. The second step involves the triggering of antibody synthesis which is initiated by persisting antigen. 5 )A model of cellular events is proposed and discussed.