Interaction of group A type 1 streptococcal M protein with fibrinogen.

Adsorption chromatography of streptococcal extracts on immobilized fibrinogen allows isolation of components that are linked to the corresponding receptors. In this study it is shown by an indirect bactericidal test that fibrinogen binds the M proteins of the streptococcal strains used. Phage-associated lysin extracts of group A type 1 streptococci precipitated with fibrinogen in a double-diffusion test. Fibrinogen reactive components of other streptococcal types inhibited this precipitation reaction. This suggests that the fibrinogen receptors in different types of group A streptococci have identical activity. The interaction between M protein and fibrinogen does not interfere with the interaction between M protein and the corresponding type specific antibodies. The streptococcal antigen components isolated by immobilized fibrinogen showed mitogenic activity in a lymphocyte transformation test.