If a mycobacterium infected macrophage is treated with pro-inflammatory cytokines, say IL-6 and IL-12, which cytokine amongst the two would ensure lesser number of intracellular bacteria than control? Suppose if the mycobacterium infected macrophages without treating with any cytokines were taken as control.
If my reading is current, classically IFN-g can be augmented by IL-12, and then IFN-gamma activates macrophage killing. However, it appears that IL-12 production upon Myco infection is not sustained in macrophages, and Myco can actually suppress long term IL-12 production see for e.g:
http://www.jleukbio.org/content/71/1/80.full
IL-6 production is stimulated by Myco and IL-6 then antagonizes IFN-gamma action. e.g.: http://www.jimmunol.org/content/171/9/4750.full
However, adding exogenous IFNg +/- IL-12 to macrophages prior to infection can overcome resistance to phagocytosis. This again is timing and concentration dependent.(above paper).
Then you have Il-18, IL-23 and IL-27.
See this for a review : http://www.ncbi.nlm.nih.gov/pubmed/17702558
Good luck !
IL-12 is generally described as a pro-inflammatory cytokine, but it has very few directly proinflammatory activities: instead it promotes the production of molecules like IFN-gamma and TNF-alpha which have a direct effect. Both of these activate macrophages to kill pathogens, by different methods.
Which is more effective depends on what the pathogen is, and therefore, which pathways are most effective against it. IFN-gamma is very effective at activating pathways centered around antimicrobial activity in the lysosome pathway, but loses effect against pathogens such as M. tuberculosis that block the development of the phagosome into a lysosome. TNF-alpha in contrast can promote the death of infected macrophages by apoptosis or autophagy and is therefore is effective against these pathogens, but at the cost of cell death.
Both of these cytokines also have many other functions. Without more detail, it's hard to be precise about which is "best".
Thank you so much all of you!....But actually I wanted to know something else relating to my previous question... as we know that the survival of intracellular pathogens in macrophages depends on the levels of pro-inflammatory & anti-inflammatory cytokines. Now suppose if we treat some of the Mycobacterium infected cells separately with IL6 & some with IL12 and some are kept untreated. Then, which cells would you expect to contain more intracellular bacteria than the untreated cells and why?
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