Cytokine gene expression in innately susceptible BALB/c mice and relatively resistant C57BL/6 mice during infection with virulent Burkholderia pseudomallei - PubMed (original) (raw)

Cytokine gene expression in innately susceptible BALB/c mice and relatively resistant C57BL/6 mice during infection with virulent Burkholderia pseudomallei

G C Ulett et al. Infect Immun. 2000 Apr.

Abstract

Production of cytokines including gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) is an important early-stage host response following infection with intracellular pathogens. Development of immunity to these pathogens is determined to a large extent by the timing and relative level of expression of the cytokines. Numerous studies have shown that early cytokine responses involving interleukin-12 (IL-12) and IFN-gamma are important for resistance to intracellular pathogens, whereas responses involving IL-4 and IL-10 increase host susceptibility. These often-indistinct early cytokine responses influence the differentiation of naïve CD4(+) T helper cells, which later develop into what have commonly been termed Th1- and Th2-type cells. The characterization of CD4(+) T-helper-cell responses as Th1 or Th2 type is based largely on the cytokine profiles during the specific phase and has been used in recent years to account for the innate resistance and susceptibility of different inbred strains of mice to several intracellular pathogens. Studies investigating cytokine production in terms of CD4(+) T-helper-cell polarization in Burkholderia pseudomallei infection have not been undertaken. In this study, we used semiquantitative reverse transcription-PCR to assess induction of cytokine mRNA in liver and spleen of B. pseudomallei-susceptible BALB/c and relatively resistant C57BL/6 mice following infection with virulent B. pseudomallei. The levels of mRNA for IFN-gamma, TNF-alpha, IL-1beta, IL-6, IL-10, and IL-12 increased in both BALB/c and C57BL/6 mice 24 to 36 h after infection. A comparison of BALB/c and C57BL/6 responses revealed the relative levels of expression of mRNA for several of these cytokines, including IFN-gamma, were greater in BALB/c mice, suggesting a role for endotoxic shock and cytokine-mediated immunopathology in the development of acute melioidosis. Early induction of mRNA for the cytokines classically associated with development of Th1- and Th2-type responses was absent or minimal, and induction levels in both strains of mice were similar. During the specific phase, cytokine mRNA profiles occurred as a combination of Th1- and Th2-type patterns. Collectively, these results demonstrate that cytokine mRNA responses in BALB/c and C57BL/6 mice following infection with virulent B. pseudomallei do not develop as polarized Th1- or Th2-type profiles. Considering the role of TNF-alpha and IFN-gamma in the processes of endotoxic shock, these results also indicate that selected cytokines, while important for resistance to B. pseudomallei infection, are also potential contributors to immunopathology and the development of acute fulminating disease.

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Figures

FIG. 1

FIG. 1

Cytokine mRNA responses in liver of C57BL/6 and BALB/c mice infected i.v. with 2.5 × 102 CFU of virulent B. pseudomallei. At various times after infection (0 to 96 h and 7 and 14 days), liver was excised and total RNA was extracted. Genomic DNA was removed, and cDNA was subjected to PCR using cytokine-specific primers. Molecular weight markers (M) are shown in the left lane of each gel. Data are representative of three mice at each time point.

FIG. 2

FIG. 2

Cytokine mRNA responses in spleen of C57BL/6 and BALB/c mice infected i.v. with 2.5 × 102 CFU of virulent B. pseudomallei. At various times after infection (0 to 96 h and 7 and 14 days), spleen was excised and total RNA was extracted. Genomic DNA was removed, and cDNA was subjected to PCR using cytokine-specific primers. Molecular weight markers (M) are shown in the left lane of each gel. Data are representative of three mice at each time point.

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