Genetic regulation of macrophage production in response to surface components of Listeria monocytogenes

Resistance to murine listeriosis requires humoral factors which alter production or delivery of monocytes to infective foci. Production of such factors is under genetic control and may be modulated by bacterial components. Two components from Listeria monocytogenes, monocytosis producing activity (MPA) and immunosuppressive activity (ISA) were used to study monocytopoiesis in mice with known abnormalities in microphage-related functions. Listeria-sensitive A/J mice fail to produce or respond to MPA or an endogenous mediator of monocytosis (EF). These studies provided evidence that a second humoral factor, decreases monocytopoiesis. Sera from A/J mice are more active in this respect and MPA treatment increases the amount of inhibitory factor in A/J mice. A polyclonal B cell activator, ISA, which induces suppressor splenic macrophages, suppresses the anti-SRBC response in resistant B10. A mice but not in A/J mice. ISA induced no change in prostaglandin E2 production by spleen cells of either strain. One interpretation of these findings is that A/J mice after stimulation by ISA or MPA, produce a substance which inhibits development of mononuclear phagocytes.