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Infection and Immunity, March 2006, p. 1916-1923, Vol. 74, No. 3
0019-9567/06/$08.00+0 doi:10.1128/IAI.74.3.1916-1923.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401
Received 29 June 2005/ Returned for modification 22 August 2005/ Accepted 11 December 2005
Toxoplasma gondii-infected macrophages are blocked in production of the proinflammatory cytokines interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-
) upon activation with lipopolysaccharide (LPS). Here, we used pathway-focused cDNA arrays to identify additional T. gondii-regulated transcriptional responses. Parasite infection decreased 57 (inclusive of IL-12 and TNF-
) and increased expression of 7 of 77 LPS-activated cytokine and cytokine-related genes. Interestingly, we found that the LPS-induced transcriptional response of the anti-inflammatory cytokine IL-10 was synergistically increased by T. gondii, results that we validated by conventional reverse transcription-PCR and enzyme-linked immunosorbent assay. Importantly, although the parasite exerted disparate effects in LPS-signaling leading to TNF-
versus IL-10 production, both responses required functional Toll-like receptor 4. We suggest that these effects represent parasite defense mechanisms to avoid or delay induction of antimicrobial activity and/or T-cell-mediated immunity during Toxoplasma infection.
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