Inflammatory mediators in culture filtrates of Escherichia coli

Escherichia coli, when cultured on a simple medium containing only glucose and inorganic compounds, release soluble factors which have a variety of biologic effects on cells in vitro. These low molecular weight (less than 12,000) substances are capable of: a) reversibly inhibiting the migration of macrophages, b) causing chemotactic attraction of neutrophils, c) inducing blast transformation of lymphocytes, and d) producing cytotoxic effects on mouse fibroblasts in culture. Although these activities are functionally similar to those which have been described for various lymphokines obtained from antigen-activated lymphocyte cultures, lymphocyte and bacterial factors which share a given property do not appear to be identical. For example, the bacterial factor which inhibits macrophage migration is partially heat labile and is dialyzable, characteristics which distinguish it from conventional migration inhibition factor. Nevertheless, similarity of function may imply the existence of some degree of chemical homology which would have importance implications concerning the evolution of host-defense reactions. In any case, as is the situation for the lymphokines, the in vitro behavior of the bacterial factors suggest a role for them in in vivo inflammatory responses.