Early interleukin 12 production by macrophages in response to mycobacterial infection depends on interferon gamma and tumor necrosis factor alpha.

Interleukin 12 (IL-12) produced by macrophages immediately after infection is considered essential for activation of a protective immune response against intracellular pathogens. In the murine Mycobacterium bovis Bacillus Calmette-Guérin (BCG) model we assessed whether early IL-12 production by macrophages depends on other cytokines. In vitro, murine bone marrow-derived macrophages produced IL-12 after infection with viable M. bovis BCG or stimulation with LPS, however, priming with recombinant interferon gamma (rIFN-gamma) was necessary. In addition, IL-12 production by these macrophages was blocked by specific anti-tumor necrosis factor alpha (TNF-alpha) antiserum. Macrophages from gene deletion mutant mice lacking either the IFN-gamma receptor or the TNF receptor 1 (p55) failed to produce IL-12 in vitro after stimulation with rIFN-gamma and mycobacterial infection. In vivo, IL-12 production was induced in spleens of immunocompetent mice early during M. bovis BCG infection but not in those of mutant mice lacking the receptors for IFN-gamma or TNF. Our results show that IL-12 production by macrophages in response to mycobacterial infection depends on IFN-gamma and TNF. Hence, IL-12 is not the first cytokine produced in mycobacterial infections.

Postdural puncture headache: a literature review.

This is a review of literature from 1943 to mid-1989 on the postdural puncture headache. The article looks at the currently held thoughts on the cause, prevention, and treatments of this second most frequent side effect of spinal anesthesia. Postdural puncture headache (PDPH) is caused by vascular distension within the nondistensible cranium following the leakage of cerebral spinal fluid (CSF) into the epidural space. Prevention of PDPH can be accomplished by using small-gauge needles and possibly by using the lateral approach, as opposed to the midline approach. Luck plays a big part, because if the needle punctures a thicker portion of the dura, there is a reduced chance of PDPH. Epidural saline injection is effective only if it is used as a continuous infusion for 24 hours. The usefulness of caffeine sodium benzoate with a 70-80% success rate and epidural blood patching with a 90%-plus success rate are discussed.

NADPH diaphorase staining suggests a transient and localized contribution of nitric oxide to host defence against an intracellular pathogen in situ.

Nitric oxide (NO) is formed constitutively in neurons by the constitutive enzyme NO synthase (cNOS) and acts as a neurotransmitter. It has already been shown that cNOS-containing neurons are identical to neurons staining for NADPH diaphorase and vice versa. Effector cells of the immune response produce high NO levels after appropriate stimulation and this NO is formed by inducible NO synthase (iNOS). The NO produced by macrophages is considered an important effector molecule of antimicrobial host defence. We have applied NADPH diaphorase staining for the detection of NO producing cells in situ during infection with an intracellular pathogen. Macrophages which produce NO in vitro are stained for NADPH diaphorase. Expression of iNOS mRNA and macrophage NADPH diaphorase staining was inhibited by iNOS-specific antisense oligonucleotides. These data suggest coincidental similarity between NADPH diaphorase activity and NO production by macrophages. Cells staining for NADPH diaphorase were identified in cryostat frozen sections of livers from mice infected with the intracellular pathogen, Listeria monocytogenes, and co-localized with cells labelled by MAC-1 mAbs. The purple-blue reaction product of NADPH diaphorase staining was visible in discrete granulomatous lesions but was absent from the liver parenchyma. Our results provide direct evidence for localized and transient participation of NO in antimicrobial immunity in the infected organ. This restriction may focus NO production to lesions, leaving unrelated tissue sites unaffected.

Growth inhibition of Mycobacterium bovis by IFN-gamma stimulated macrophages: regulation by endogenous tumor necrosis factor-alpha and by IL-10.

Murine bone marrow-derived macrophages (BMM) are able to inhibit the intracellular growth of Mycobacterium bovis and Mycobacterium tuberculosis H37Rv after activation with recombinant (r) IFN and growth inhibition is mediated by reactive nitrogen intermediates (RNI) derived from L-arginine. We now demonstrate that tumor necrosis factor (TNF)-alpha acts as an endogenous cofactor in the induction of mycobacterial growth inhibition. TNF-alpha was produced by BMM stimulated with rIFN-gamma and infected with mycobacteria, and a specific antiserum to TNF-alpha inhibited rIFN-gamma-induced production of RNI as well as growth inhibition of M. bovis. IL-10, a cytokine which suppresses antimycobacterial macrophage functions, was also produced by BMM activated with rIFN-gamma and infected with M. bovis. IFN-gamma-induced production of TNF-alpha and of reactive nitrogen intermediates as well as mycobacterial growth inhibition were inhibited by exogenous IL-10, but only when given prior to IFN-gamma stimulation. We conclude that the outcome of mycobacterial infection is regulated by a coordinate interplay between IFN-gamma, TNF-alpha and IL-10.