Effect of Concanavalin a in Vivo in Suppressing the Antibody Response in Mice

Adult mice injected intraperitoneally with concanavalin A 2 days prior to primary immunization with a thymus-dependent, sheep erythrocyte antigen by the same route, showed a marked suppression of their immunoglobulin response as measured by a plaque-forming spleen cell assay. The effect was less pronounced or not demonstrable if the concanavalin A was injected at longer intervals before, at the same time as, or after antigen. A comparable immunosuppression was seen in the secondary response to sheep erythrocytes injected 10 days apart, provided the concanavalin A was injected 2 days prior to the second injection of antigen. Treatment with concanavalin A 2 days prior to the first injection of antigen had no effect upon the secondary response. It was also shown that concanavalin A treatment did not suppress the immunoglobulin response to a thymus-independent, Escherichia coli lipopolysaccharide antigen. The most striking immunosuppression was observed when both concanavalin A and antigen were injected by the same route, either intraperitoneally or intravenously.