Reduced toxoplasmastatic activity of monocytes from AIDS patients: a role for granulocyte-macrophage colony-stimulating factor.

In the present study the role of granulocyte-macrophage colony stimulating factor (GM-CSF) in the reduced toxoplasmastatic activity of monocytes was investigated in patients with acquired immunodeficiency syndrome (AIDS). The secretion of GM-CSF by non-stimulated monocytes and by Toxoplasma gondii-infected monocytes from AIDS patients did not differ from that of healthy individuals. Furthermore, GM-CSF was not detected in sera from AIDS patients and healthy individuals. However, upon stimulation with lipopolysaccharide (LPS), monocytes from AIDS patients released significantly more GM-CSF than those from healthy individuals. Incubation of monocytes from AIDS patients with polyclonal antibodies against GM-CSF restored their inhibitory activity against T. gondii. On the basis of the present and earlier results the putative mechanism of reduced toxoplasmastatic activity of monocytes from AIDS patients may be as follows: upon stimulation with human immunodeficiency virus (HIV) the increased synthesis of GM-CSF by monocytes stimulates the production of prostaglandin E2 (PGE2) which, in turn, impairs the toxoplasmastatic activity of these cells.