Activation of murine macrophages and a bovine monocyte cell line by bovine lymphokines to kill the intracellular pathogens Eimeria bovis and Toxoplasma gondii.
Macrophage (M phi)-activating lymphokines present in concanavalin A-stimulated bovine T-lymphocyte cultures (ConAS) were studied by assessing their effects on Eimeria bovis and Toxoplasma gondii growth in cultured bovine monocytes (BM) and mouse M phi. The in vitro development of both parasites was assessed by incorporation of [3H]uracil and by microscopic examination of parallel cultures. Incorporation of [3H]uracil into infected cultures was an accurate indicator of growth of both E. bovis and T. gondii in BM and mouse M phi. Sporozoites of E. bovis underwent merogony in untreated BM but not in mouse M phi, whereas T. gondii developed in both cell types. Inhibition of T. gondii growth was greatest in ConAS-treated BM, whereas preincubation of mouse M phi with ConAS resulted in about 80% growth inhibition. There was no significant difference between the inhibition of either T. gondii sporozoite- or tachyzoite-induced growth in ConAS-treated cells, showing that activation pathways are equally effective against both stages. Treatment of ConAS with glycine-hydrochloride buffer (pH 2) resulted in a total loss of antiviral activity mediated by gamma interferon (IFN-gamma). When pH 2 dialyzed ConAS was used to activate BM, inhibition of T. gondii growth was only partially affected. Because bovine IFN-gamma does not activate mouse M phi and due to the partial effects of pH 2 on ConAS-induced growth inhibition, the major component(s) of ConAS responsible for T. gondii growth inhibition is distinct from IFN-gamma. Furthermore, IFN-gamma may act synergistically rather than being part of a priming sequence for M phi responsiveness to other lymphokines. Murine recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) was tested for any microbistatic activity against T. gondii sporozoites and tachyzoites. There was no significant difference in either colony formation or [3H]uracil incorporation between rGM-CSF-treated and control cultures, regardless of host cell type. Thus, rGM-CSF does not induce adequate M phi activation to kill T. gondii and is not a major microbistatic component of ConAS. rGM-CSF also had no effect on T. gondii infection in vivo.
D000818:Animals; D002417:Cattle; D003115:Colony-Stimulating Factors / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology; D004539:Eimeria / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007371:Interferon-gamma / Q000494:pharmacology; D008222:Lymphokines / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects*; D008264:Macrophages / Q000276:immunology / Q000469:parasitology; D008297:Male; D051379:Mice; D009000:Monocytes / Q000276:immunology* / Q000469:parasitology; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014122:Toxoplasma / Q000502:physiology*
D003115:Colony-Stimulating Factors; D008222:Lymphokines; D003208:Concanavalin A; D007371:Interferon-gamma