The activity of partially purified leukocytic endogenous mediator in endotoxin-resistant C3H/HeJ mice.

Partially purified LEM was injected into both the endotoxin-resistant C3H/HeJ and the closely related, but endotoxin-responsive, C3Heb/FeJ strains of mice. Both strains of mice responded to LEM with significant decreases in plasma iron concentration, increased number of peripheral blood neutrophils, increased plasma levels of CSA, and elevations of plasma fibrinogen concentration. Injections of endotoxin produced significant responses in these four determinations in C3Heb/FeJ mice but had no effect in the C3H/HeJ strain. Changes in plasma iron, fibrinogen, CSA, and neutrophils are believed to occur when LEM is produced by an interaction of endotoxin with phagocytic cells.