Spleen cells from animals tolerant to a thymus-dependent antigen can be activated by lipopolysaccharide to synthesize antibodies against the tolerogen.

Immunological tolerance was induced in adult mice by the injection of 5 mg of deaggregated hapten-protein conjugate. The tolerant state was confirmed 4-19 days later by the failure of such animals to mount an immune response against an aggregated form of the same thymus-dependent hapten-protein conjugate as well as by the inability of spleen cells from tolerant animals to respond to a thymus-independent hapten-carrier conjugate. Even though the …