Influence of reticuloendothelial blockade on the induction of tolerance and immunity by polysaccharides.

The intensity of reticuloendothelial blockade by carrageenan, silica and ethyl stearate was measured and its effect studied on the susceptibility to tolerance induction by polysaccharide antigens in mice. The most intense RE depression reduced the tolerance threshold dose of levan only by 3-fold and that of dextran B512 not at all. The genetic resistance of BALB/c mice to tolerization with the alpha1-3 glucose epitope of dextran B1355 was not overcome by carrageenan blockade which did however, render them normally susceptible to tolerance induction by human gamma-globulin. PFC responses to immunization by the polysaccharides were diminished by blockade, relative to its intensity and to the antigen itself. These and other data suggest that severe RE blockade (a) can promote tolerance by suppressing the active role(s) of the macrophages in immune induction rather than by sustaining circulating antigen, and (b) depresses responses to thymus-independent antigens, probably by an immunosuppressive influence mediated by damaged macrophages.