Because macrophage migration inhibitory factor (MIF) is a key cytokine in pregnancy and has a role in inflammatory response and pathogen defense, the objective of the present study was to investigate the effects of MIF in first-and third-trimester human placental explants infected with Toxoplasma gondii. Explants were treated with recombinant MIF, IL-12, interferon-␥, transforming growth factor-␤1, or IL-10, followed by infection with T. gondii RH strain tachyzoites. Supernatants of cultured explants were assessed for MIF production. Explants were processed for morphologic analysis, immunohistochemistry, and real-time PCR analysis. Comparison of infected and stimulated explants versus noninfected control explants demonstrated a significant increase in MIF release in first-trimester but not third-trimester explants. Tissue parasitism was higher in third-than in first-trimester explants. Moreover, T. gondii DNA content was lower in first-trimester explants treated with MIF compared with untreated explants. However, in third-trimester explants, MIF stimulus decreased T. gondii DNA content only at the highest concentration of the cytokine. In addition, high expression of MIF receptor was observed in first-trimester placental explants, whereas MIF receptor expression was low in third-trimester explants. In conclusion, MIF was up-regulated and demonstrated to be important for control of T. gondii infection in first-trimester explants, whereas lack of MIF up-regulation in third-trimester placentas may be involved in higher susceptibility to infection at this gestational age.

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In Chagas disease, understanding how the immune response controls parasite growth but also leads to heart damage may provide insight into the design of new therapeutic strategies. Tumor necrosis factor-alpha (TNF-α) is important for resistance to acute

Chemokines comprise a structurally related family of cytokines that regulate leukocyte trafficking. Because infection with Toxoplasma gondii can induce an important inflammatory reaction that, if left uncontrolled, can lead to death, we investigated the role of the chemokine receptor CCR2 in T. gondii infection. We orally infected CCR2 ؊/؊ mice with five ME-49 T. gondii cysts and monitored morbidity, survival, and immune response thereafter. The CCR2 ؊/؊ mice displayed higher susceptibility to infection as all mice died on day 28 after infection. Despite similar Th1 responses, a more evident anti-inflammatory response was induced in the peripheral organs of CCR2 ؊/؊ mice compared with wild-type C57BL/6 mice. Additionally, CCR2؊/؊ mice presented greater parasitism and a milder inflammatory reaction in their peripheral organs with lesser CD4 ؉ and MAC-1 ؉ and greater CD8 ؉ cell migration. The parasite load decreased in these organs in CCR2 ؊/؊ mice but remained uncontrolled in the central nervous system. Additionally, we observed down-regulated inducible nitric oxide synthase expression in peripheral organs from CCR2 ؊/؊ mice that was associated with a small nitric oxide production by spleen macrophages. In conclusion, in the absence of CCR2, another mechanism is activated to control tissue parasitism in peripheral organs. Nevertheless, CCR2 is essential for the activation of microbicidal mediators that control T. gondii replication in the central nervous system.

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