A mechanism of migration inhibition involving components of the coagulation system.

Lymph from pigs given bacillus Calmette-Guérin (BCG) and stimulated in the drainage area of a cannulated lymph node with tuberculin (PPD) had potent in vitro macrophage migration inhibitory activity. A similar observation has previously been made in sheep by other workers. In the sheep, part of, and in the pig, almost all of, this inhibitory activity was produced, not by a factor resembling the so-called 'migration inhibitory factor', but by a mechanism involving a protease and fibrinogen. It is suggested that exudate cells, having potent coagulation-promoting activity, can promote the deposition of fibrin about themselves, and thus 'trapped' are unable to migrate.