Circulating cytokine concentrations in tuberculosis and other chronic bacterial infections

Cytokines are a group of hormone-like polypeptides that play a variety of r egulatory roles in host defense against infection. Because of the possible different involvement of these mediators in bacterial infections and tuberc ulosis, enzyme immunoassay was used to measure comparatively the plasma lev els of the proinflammatory cytokines interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6) and interferon gamm a (IFN-gamma) in 25 immunocompetent patients divided into two groups: in 12 patients clinical and microbiological diagnosis showed a chronic bacterial infection and 13 patients had pleuropulmonar tuberculosis. After resolutio n of the infectious disorders (greater than or equal to 3 months), these me asurements were repeated for each patient. High levels of IL-1b, TNF-alpha and IL-6 were observed at study entry, but no significant difference was fo und between the groups. In contrast, plasma levels (mean +/- SEM) of IFN-ga mma were significantly higher in patients with tuberculosis when compared w ith the bacterial group (0.753 +/- 0.201 vs 0.325 +/- 0.105 IU/ml; P = 0.02 0). This different pattern of plasma proinflammatory cytokines could be asc ribed to a prevaling role of the mediators of so-called Th-1 immune respons e (IFN-gamma) in host defense against infection with Mycobacterium tubercul osis.