Deficiency of the macrophage migration inhibitory factor gene has no significant effect on endotoxaemia

By targeted disruption of the MIF gene, we have established a mouse strain deficient in macrophage (M phi) migration inhibitory factor (MIF). Despite previous reports indicating an essential role of MIF in endotoxaemia, an injection of lipopolysaccharide (LPS) into the MIF-deficient mice (maintained under specific pathogen-free conditions) caused shock. No significant difference was detected between the MIF-deficient mutant and normal mice in susceptibility to LPS for endotoxaemia or tumour necrosis factor-alpha (TNF-alpha) formation upon LPS injection. Peritoneal M phi from the two strains produced TNF-alpha in response to LPS with similar dose responses. Dexamethasone suppressed the LPS-induced TNF-alpha response of M phi, but no difference was detected between the M phi from the two strains. These results suggest that endogenous MIF has no significant effect on the LPS-induced TNF-alpha production and no effect on suppression of the response by glucocorticoids. Thus, MIF is not crucial for LPS-induced immune responses leading to shock.