Abstract:

The cell-sensitizing factor (SF) of group A streptococci is a teichoic acid which can sensitize mammalian cells to agglutination and lysis in the presence of anti ·SF antibodies and complement. SF is highly immunogenic in the rabbit when bound naturally to some constituent of the streptococcus cell, but only feebly so when it is extracted from the cells by phenol. Both rabbit and human antibodies to SF, which are mainly associated with the macroglobulin fraction (IgM) of serum, are destroyed by treatment with 2-mercaptoethanol. While human anti-SF antibodies are readily destroyed by freezing and thawing and by heating to 58 C, the rabbit anti-SF antibodies are not destroyed at 64 C and are relatively resistant to repeated freezing and thawing. Complexes formed between SF and rabbit antibodies fix complement both in the absence and presence of red blood cells (RBC). Anti-SF antibodies interact with SF and prevent the latter from sensitizing RBC. Rabbits immunized with heat-killed streptococci and which developed anti-SF antibodies, developed severe arthritis when SF was injected into their knee joints. The arthritic lesions were characterized by a marked proliferation of the synovial membrane, a chronic inflammatory exudate and the accumulation of large numbers of lymphocytes in the form of "pseudolymphatic follicles." Nonimmunized animals failed to develop such lesions. It is suggested that sensitization of cells with SF during streptococcal infection may lead to passive immune cytolysis and may thus contribute to the pathogenicity of streptococci.