Streptokinase is able to bind to and activate human plasminogen, a blood clot-dissolving protein, but not the plasminogens from other mammalian species.129 The plasminogen-activating activity of streptokinase has been implicated in the accelerated clearance of host fibrin, which may promote the dissemination of S. pyogenes in host tissues.128,130 Mice typically possess high resistance to skin infection by S. pyogenes, but Sun et al. 128 showed that the expression of human plasminogen in mice led to markedly increased mortality in the transgenic mice when infected with streptococci. Here, PLG is linked to skin infection.