Immunology Letters 77 (2001) 31 – 38 Bone marrow-derived macrophages grown in GM-CSF or M-CSF differ in their ability to produce IL-12 and to induce IFN- production after stimulation with Trypanosoma cruzi antigens Carlos Eduardo Tadokoro, Ises de Almeida Abrahamsohn * Departamento de Imunologia, Instituto de Cie ˆncias Biome ´dicas, Uniersidade de Sa ˜o Paulo, A. Prof. Lineu Prestes, 1730, Ed. Biome ´dicas IV, Sa ˜o Paulo, 05508 -900, S.P., Brazil Received 5 December 2000; accepted 1 March 2001 Abstract Trypanosoma cruzi is the etiological agent of Chagas’ disease in man. Control of parasitism at the beginning of experimental infection depends on cytokine-activated macrophages that synthesize nitric oxide (NO). We investigated macrophage populations derived in the presence of M-CSF (M-MØ) or GM-CSF (GM-MØ) regarding their ability to control intracellular parasitism by T. cruzi and to synthesize IL-12 and NO. Both macrophage populations supported intracellular multiplication of the parasite; when activated by IFN-, GM-MØ exerted better control of parasitism. Stimulation of GM-MØ with T. cruzi or Staphylococcus aureus resulted in IL-12 production and higher levels of NO synthesis in comparison with stimulated M-MØ. Mice immunized with parasite-Ag-pulsed GM-MØ but not with pulsed M-MØ had increased IFN- and IL-2 production in lymph nodes. However, when immunization was followed by infection with live parasites, transient elevation of IFN- production was observed in both GM-MØ- and M-MØ-immunized mice, without reduction of blood parasite levels. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Macrophages populations; Nitric oxide; Cytokines; GM-CSF; M-CSF; Chagas’ disease www.elsevier.com/locate/ 1. Introduction Infection with the protozoan parasite Trypanosoma cruzi results in a life-long infection, which can lead to Chagas’ disease, a debilitating illness affecting heart or digestive function in 30% of chronic phase-patients. T. cruzi can infect macrophages amongst a variety of other host cell types; intracellular replication occurs as amastigotes followed by the release of trypomastigotes that can be carried by the bloodstream to infect all organs. Control of T. cruzi parasitism during the first weeks of infection is considered to be critically dependent on effective macrophage activation by cytokines. Evidence has accumulated showing that the addition of IFN- [1–4], GM-CSF [5,6] or TNF- [4,5] to cultures of T. cruzi -infected macrophages results in more efficient killing of amastigotes by the phagocytes. The in vivo administration of IFN- [7], TNF- [8] or IL-12 [9] early during infection effectively reduces blood para- sitism and mortality. Intracellular killing of T. cruzi by IFN-- or TNF- -activated macrophages is mediated largely by nitric oxide [4]. IFN- synthesis at the initial phase of infec- tion is IL-12 dependent [10,11] and important for the control of T. cruzi infection by innate [9] and acquired immunity [10,11]. In the murine model of Leishmania major infection, immunization with parasite-antigen pulsed macro- phages grown in GM-CSF (GM-MØ), but not with similarly pulsed macrophages grown in M-CSF (M-MØ), stimulates IFN- production in draining lymph nodes (LN) and increases the resistance of sus- ceptible BALB/c mice to infection [12]. This study indicates that the type of macrophage that interacts with antigen (Ag) in vivo may influence the immune * Corresponding author. Tel.: +55-11-38187383; fax: +55-11- 38187224. E-mail address: iabraham@usp.br (I. de Almeida Abrahamsohn). 0165-2478/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0165-2478(01)00197-3