A cytoplasmic component of group A streptococci suppresses both 19S and 7S antibody responses of mice to sheep erythrocytes. Partial purification is achieved by differential centrifugation and gel filtration. When the direct and indirect hemolytic plaque techniques are used, a single injection of this group A material given before injection of erythrocytes produces more than 90-percent suppression of either primary or secondary immune response.
The presence of cell mediated immunity to Echinococcus granulosus antigen was detected in syngeneic mice with secondary hydatidosis. Significant increases of thymidine uptake were observed in spleen cells from infected animals exposed to protoscolex or hydatid fluid antigens. A definite decrease in the number and size of cysts occurred in mice following the simultaneous intraperitoneal injection of viable protoscolices and a suspension of 1 x 10(7) sensitized spleen cells.
A component in extracts of Group A streptococci suppresses antibody formation in mice against heterologous erythrocyte and protein antigens. Large doses are not toxic and repeated injection does not change its effectiveness. It is most effective when injected 1 or 2 days before antigen and it is not suppressive when given after antigen. The active factor occurs as a large polydisperse complex and activity can be increased 10- to 25-fold by filtration through Sepharose 2B. Both direct (γM) and indirect (γG) antibody-forming cells are suppressed in primary and secondary responses. Injection before a primary response does not reduce memory cell development. It increases rather than depresses the "background" antibody-forming cells to sheep erythrocytes, and is equally effective if injected intraperitoneally or intravenously. Ribonuclease increases activity while deoxyribonuclease has no effect. Proteases destroy immunosuppressive action.
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