Mouse C-Reactive Protein and Endotoxin-Induced Resistance

Abstract

The relationship between the level of C-reactive protein (CRP) in the sera of mice and resistance to Staphylo-coccus aureus infection after the injection of Escherichia coli endo-toxin was studied. The CRP level was essentially unchanged at 6 hr after endotoxin, and resistance was slightly decreased. At 24 hr after endotoxin, both CRP levels and resistance were increased. Since the increase in the CRP level and resistance appeared to be associated, it was of interest that, when the mouse CRP was tested for in vitro reactions with several strains of bacteria, cells of all species of gram-positive bacteria tested (including S. aureus) were agglutinated by CRP. E. coli was not agglutinated under the conditions of the test. It is proposed that CRP is an opsonin, and possibly a lysin, and is involved in nonspecific resistance to infection with S. aureus.