Role of tumor necrosis factor alpha (TNF-alpha) and interleukin-10 in the pathogenesis of severe murine monocytotropic ehrlichiosis: increased resistance of TNF receptor p55- and p75-deficient mice to fatal ehrlichial infection.
Intraperitoneal (i.p.) infection with a high dose of a highly virulent Ehrlichia strain (IOE) results in a toxic shock-like syndrome characterized by severe liver injury and systemic overproduction of tumor necrosis factor alpha (TNF-alpha) by CD8+ T cells. We examined the role of TNF-alpha and TNF receptors in high-dose-IOE-induced shock/liver injury. TNF receptor (TNFR) I/II-/- mice lacking both the p55 and p75 receptors for this cytokine were more resistant to IOE-induced liver injury than their wild-type background controls. TNFR I/II-/- mice survived longer, dying between 15 and 18 days, with evidence of mild liver necrosis/apoptosis. In contrast, wild-type mice were not rescued from the lethal effect of IOE by TNF-alpha neutralization. TNF-alpha-depleted mice developed severe liver injury and succumbed to disease between days 9 and 11 postinfection, similar to sham-treated, infected wild-type mice. Although IFN-gamma production in the spleens of IOE-infected TNFR I/II-/- and TNF-alpha-depleted mice was higher than that detected in wild-type controls, these mice had higher bacterial burdens than infected controls. Following high-dose IOE challenge, TNFR I/II-/- and TNF-alpha-depleted mice have an early increase in IL-10 levels in sera and spleens, which was produced mainly by adherent spleen cells. In contrast, a late burst of interleukin-10 (IL-10) was observed in control mice. Nonadherent spleen cells were the major source of IL-10 in IOE-infected wild-type mice. We conclude that TNFR I/II and TNF-alpha participate in Ehrlichia-induced shock and host defense by regulating liver injury and controlling ehrlichial burden. Our data suggest that fatal ehrlichiosis could be a multistep process, where TNF-alpha is not solely responsible for mortality.
Ismail
Nahed
N
Department of Pathology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0609, USA.
Stevenson
Heather L
HL
Walker
David H
DH
D000818:Animals; D017209:Apoptosis; D004198:Disease Susceptibility / Q000276:immunology; D004536:Ehrlichia / Q000276:immunology / Q000472:pathogenicity*; D016873:Ehrlichiosis / Q000276:immunology / Q000401:mortality* / Q000503:physiopathology; D007113:Immunity, Innate / Q000502:physiology*; D016753:Interleukin-10 / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009115:Muridae; D018124:Receptors, Tumor Necrosis Factor / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10