Demonstration of a soluble mediator that induces exudates rich in Ia-positive macrophages.

Abstract

Listeria monocytogenes-immune T cells, adoptively transferred into normal mice with killed Listeria organisms, induced peritoneal exudates rich in Ia-positive macrophages. Culture fluids generated by Listeria-immune exudate cells and Listeria contain an activity that elicits Ia-rich exudates when injected i.p. The factor that recruits Ia-positive macrophages must be injected several times during a 2 day period for optimal demonstration of its activity. Factor induction is immunologically specific and requires Ia-positive macrophages, primed T lymphocytes and antigen challenge. The factor is a nondialyzable protein and is not genetically restricted in its activity. The macrophages in the exudates induced by the factor bear Fc receptors, take up latex and synthesize I-A, but bear few C3 [complement component 3] receptors. An immune mediator capable of controlling the exudate macrophages Ia phenotype was identified.