Acute Phase Protein in Mouse Plasma

Bernheimer and Cantoni (1), in 1947, described an unusual "anti toxic" mechanism in mice, characterized by the development of a temporary state of resistance to the lethal effect of streptolysin O within hours of the intravenous administration of sublethal amounts of this toxin. Rowen and Bemheimer (2) subsequently found this induced refractoriness to be associated with an increased capacity of plasma from the treated animals to inhibit the hemolytic action of the streptococcal toxin. The substance responsible for this inhibitory activity is not antibody, but has proved to be an unusual type of low density lipoprotein that is easily and quantitatively separable from the plasma by ultracentrifugal flotation (3). In the course of efforts to immunologically characterize the streptolysin O inhibitor we have uncovered a new antigenic component, distinct from the inhibitor, in plasma of mice treated with the streptococcal toxin. The new factor is not evoked exclusively by streptolysin O; it also appears following exposure of mice to certain other toxic materials and during acute bacterial infections. The present report deals with the detection of this new "acute phase" plasma component, the conditions under which it appears, and with experiments directed to its chemical and immunological characterization.