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Original Article |
Production
Correspondence to: Margaret Neighbors, Dept. of Immunology, DNAX Research Institute, Palo Alto, CA 94304-1104. Tel:650-496-1102 Fax:650-496-1200 E-mail:margaret.neighbors{at}dnax.org.
The stimulation of interferon (IFN)-
by interleukin (IL)-12 has been shown to provide protection from intracellular pathogens such as Listeria monocytogenes. Tumor necrosis factor (TNF) is also a major player in the resolution of Listeria infections and is suggested to have more global effects than can be explained by the induction of IFN-
alone. Since IL-18 synergizes with IL-12 to induce IFN-
production by natural killer and T helper (Th)1 cells, we determined its role in responses to Listeria. IL-18 appeared to be even more potent than either IL-12 or IFN-
for protection against this pathogen and IL-18 enhanced bacterial clearance in the complete absence of IFN-
. Indeed IL-18 was comparable to TNF in its ability to resolve the infection and showed a lowered protective capacity in the absence of TNF. Moreover, IL-18 induced macrophages to secrete both TNF and nitric oxide after a Listeria infection. IL-18 was also essential for optimal IFN-
production by antigen-specific T cells. Therefore, IL-18 operates via its effects on both the innate immune response, including macrophages, as well as on Th1 cells, to protect against Listeria.
Key Words: Listeria, IL-18, TNF, NO, Th1 cells
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