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Infection and Immunity, October 1999, p. 5021-5026, Vol. 67, No. 10
Department of Biology, University of North
Carolina
Received 22 March 1999/Returned for modification 17 May
1999/Accepted 21 July 1999
Optimal immune responses against an intracellular bacterial
pathogen, such as Salmonella, involve the production of
gamma interferon (IFN-
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Limited Interleukin-18 Response in
Salmonella-Infected Murine Macrophages and in
Salmonella-Infected Mice
Charlotte, Charlotte, North Carolina 28223
), which activates macrophages. It has
recently been suggested that, interleukin-18 (IL-18), in addition to
IL-12, contributes to the induction of IFN-
following infection.
Given this hypothesis, an optimal host immune response against
intracellular bacterial pathogens would include the induction of IL-18
secretion by macrophages due to Salmonella infection. We
questioned whether Salmonella could induce macrophages to
upregulate their expression of IL-18 mRNA and secretion of IL-18. With
cultures of murine macrophages, we were surprised to find that
infection by wild-type Salmonella dublin resulted in
decreased expression of IL-18 mRNA and IL-18 secretion rather than an
increase. Reduction of macrophage-derived IL-18 expression by wild-type
Salmonella occurred early in the response, suggesting a
direct effect. Furthermore, mice orally inoculated with wild-type
Salmonella were shown to have reduced IL-18 mRNA expression
at mucosal sites within hours postinoculation. Together these studies
demonstrate Salmonella-induced reductions in IL-18
expression, suggesting that this intracellular pathogen may be capable
of limiting a potentially protective immune response.
*
Corresponding author. Mailing address: Department of
Biology, UNC Charlotte, 9201 University City Blvd., Charlotte, NC
28223. E-mail: klbost{at}emailuncc.edu. Phone: (704)
547-2909. Fax: (704) 547-3128.
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