The results of experiments, indicating the development of cell-mediated delayed hypersensitivity (DH) skin reaction, its dependence on the virulence of Shigella flexneri 2a, the dose and the character of the antigen used for testing the reaction, are presented. One of the immunologically active components of S. flexneri virulent strain 2a No. 516 is a biologically active thermolabile factor detected in filtrate and supernatant fluid. These data suggest that the immunosuppressive action of the virulent strain is probably linked with the function of T-suppressors affecting the reaction at the period of its development (the induction phase). S. flexneri avirulent strain produced no such effect, developing DH being seemingly sufficient for activating T-cell-mediated immune response.
Animals Antigens, Bacterial