The induction of immunologic tolerance with type III pneumococcal polysaccharide cross-linked or coupled to protein.

Type III pneumococcal polysaccharide molecules were linked to one another, i. e. cross-linked. The product was essentially insoluble in saline. Large pieces weighing 1-2 mg were inserted into mice. They produced immunologic paralysis or immune tolerance. When placed intraperitoneally in millipore chambers the cross-linked polysaccharide did not have any apparent effect, for the mice were not tolerized. When pneumococcal polysaccharide was linked to a protein, the amount of polysaccharide required to cause tolerance or immunity was essentially the same as the amount of free pure soluble polysaccharide. In addition, Xenopus laevis eggs were injected with a different antigen, bovine gamma globulin, and then with antibody to that antigen. Twelve of the twelve eggs so injected changed shape. Equal numbers of other eggs injected twice with the antigen or twice with the antibody did not change shape.