CRP and infection: C-reactive protein-deficient mice were dramatically more susceptible than age- and sex-matched wild-type C57BL/6 controls to lethal infection after intraperitoneal inoculation of two independent clinical isolates of virulent type 6B S. pneumoniae (strains Tz7712-2 and RF200) (Fig.4a,b), with LD50 values of < 10 and about 106 organisms, respectively (Fig.4c).