The elderly account for a disproportionate share of all tuberculosis cases, and the population ageing may not fully explain this phenomenon. We have performed in vitro infection experiments to investigate whether there is an immunological basis for the apparent susceptibility of elders to tuberculosis. In our infection model, Mycobacterium tuberculosis induces a higher production of interleukin (IL)-6 and reactive oxygen species in macrophages from elders than from younger adults. This response did not prevent, however, an increased multiplication of M. tuberculosis in macrophages from elders as compared with the growth observed within cells from adults. By performing a factorial experiment, we have found that IFN-γ, but not IL-1β, IL-6 or TNF-α, stimulate the macrophages to restrict the multiplication of the bacterium in macrophages from elders. Although monocytes from elders seem to be in a higher level of activation, we present evidences that protein tyrosine phosphorylation response induced by M. tuberculosis is stronger in monocytes from adults than from elders. Using a protein array that detects 71 tyrosine phosphorylated kinases, we identified Pyk2 as the only kinase that displayed a difference of intensity larger than 50 % in adults than in elders. Furthermore, monocytes from elders that were incubated in the presence of tyrosine kinase inhibitors (genistein and PP2) allowed a higher level of bacterial multiplication. These observations may help to explain the susceptibility of elders to tuberculosis. An unexpected result was that both genistein and its negative control, daidzein, abundant soy isoflavones, promoted intracellular mycobacterial growth.
Summary
Differences in the activity of monocytes/macrophages, important target cells of Mycobacterium tuberculosis, might influence tuberculosis progression. With the purpose of identifying candidate genes for tuberculosis susceptibility we infected monocytes from both healthy elderly individuals (a tuberculosis susceptibility group) and elderly tuberculosis patients with M. tuberculosis, and performed a microarray experiment. We detected 78 differentially expressed transcripts and confirmed these results by quantitative PCR of selected genes. We found that monocytes from tuberculosis patients showed similar expression patterns for these genes, regardless of whether they were obtained from younger or older patients. Only one of the detected genes corresponded to a cytokine: IL26, a member of the interleukin‐10 (IL‐10) cytokine family which we found to be down‐regulated in infected monocytes from tuberculosis patients. Non‐infected monocytes secreted IL‐26 constitutively but they reacted strongly to M. tuberculosis infection by decreasing IL‐26 production. Furthermore, IL‐26 serum concentrations appeared to be lower in the tuberculosis patients. When whole blood was infected, IL‐26 inhibited the observed pathogen‐killing capability. Although lymphocytes expressed IL26R, the receptor mRNA was not detected in either monocytes or neutrophils, suggesting that the inhibition of anti‐mycobacterial activity may be mediated by lymphocytes. Additionally, IL‐2 concentrations in infected blood were lower in the presence of IL‐26. The negative influence of IL‐26 on the anti‐mycobacterial activity and its constitutive presence in both serum and monocyte supernatants prompt us to propose IL26 as a candidate gene for tuberculosis susceptibility.
The genus Janibacter comprises nine different species mainly found in the environment. Only two human infections by these microorganisms have been previously reported, one by J. melonis and another one by an undescribed Janibacter sp. Herewith we report the first human cases of infection by J. terrae in four bacteremic patients. The microorganisms were isolated from two consecutive blood cultures taken from four febrile patients with several underlying conditions. All patients were treated with antibiotics, two of them with favorable outcome. Two severely immunocompromised patients died, and one was treated with an antibiotic in vitro active against the isolate. Janibacter terrae was identified by phenotypic and 16S rDNA amplification methods. This report includes also the first data on antimicrobial susceptibility of this opportunistic pathogen. Clinical microbiologists should be aware of this microorganism which can be identified by phenotypic and molecular methods.
pneumophila, supporting its role in the modulation of the antimicrobial activity. Finally, U937 cells transfected with the NAP-2 construct showed an adherence that was dramatically enhanced when the substrate was fibronectin. We conclude that human phagocytes produce CXCL7 variants that may have a significant influence on the immune response against bacterial pathogens.3
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.