We therefore assayed the supernates

from groups undergoing enhanced apoptosis for those 2 cytokines (some individuals were excluded), and a proportional increase of TNF-α levels was evident only for the HD group (Fig. 3a; p < 0.004). However, this finding did not mirror that of the UV group since the rates of TNF-α remained undetectable even in the presence of BCG infection at both time-points. Also, there was a statistically significant difference at 24 h of infection when HD and UV groups were compared (p = 0.03). The pro-inflammatory cytokine IL-1β, for which cell-death induction is also one of its main functions [8], was also assayed. There was a marked MG-132 purchase increase in IL-1β levels that were directly proportional to the time of BCG infection in the HD group ( Fig. 3b; p ≤ 0.02). This pattern was also a trend in the UV group, but opposite to TNF-α, although it did not attain a statistically significant difference when compared to the baseline condition. Also, no discrepancy was found when evaluating the IL-1β levels between the 2 cohorts Gefitinib cell line in this last, resting condition (p = 0.85). It has been previously shown that mycobacteria are able to induce macrophage apoptosis, and the inhibition of this critical mechanism might be considered an evasive strategy of the pathogen [Reviewed by 6]. Evasion of apoptosis

by M. tuberculosis can be achieved in human macrophages by enhanced release of sTNFR2 [6], Mcl-1 [10], bcl-2 PAK6 and Rb [11], and lower productions of prostaglandin E2 [12], bad and bax, and caspases-1, -3 and -10 [11]. On the other hand,

necrosis can be looked at as a good strategy induced by pathogenic mycobacteria to skew the protective host immune response. Since 2005, a novel form of proinflammatory programmed cell death, or pyroptosis, has been identified to be uniquely dependent on caspase-1, which is not involved in apoptosis, and prototypically induced by infection with flagellin-expressing bacteria, such as Salmonella and Shigella species [13]. To date, pyroptosis seems to play a significant role in specific biological systems. It has been previously shown that this mechanism releases bacteria from macrophages and exposes the bacteria to uptake and killing by reactive oxygen species in neutrophils [14]. Similarly, activation of caspase-1 cleared intracellular Legionella pneumophila and Burkholderia thailandensis in vivo by IL-1β-independent mechanisms, an efficient bactericidal mechanism by the innate immune system [14]. In this study, we did not check whether pyroptotic cell death takes place in our system; however, based on the latest notion highlighted by those authors, the increased IL-1β levels found in the cultures could not support this possibility. With this in mind, and regarding M.