The lack of thymic influence in regulating the immune response to Escherichia coli 0127 endotoxin.

A possible regulatory effect of thymus-derived lymphocytes on the immune response to a thymus independent antigen, Escherichia coli 0127 somatic antigen in mice, was investigated. Antilymphocyte globulin prepared in rabbits caused a substantial suppression of the antibody response to a thymus dependent antigen (sheep erythrocytes) but exerted no effect on the immune response to the bacterial antigen. Administration of E. coli somatic antigen to mice did not induce an immunosuppressive effect on a subsequently injected unrelated antigen indicating that this thymus independent antigen was incapable of inducing antigenic competition. Likewise, the immune response to the bacterial antigen was not influenced by prior immunization of the mice with sheep erythrocytes. Thus, in these immune reactions in which thymus-derived lymphocytes were affected the response to the bacterial antigen was not modified. These results contradict recent observations which indicated that thymus-derived lymphocytes exert a suppressive effect on the immune response to thymus independent antigens.