Serum IL-1β and IL-18 correlate with ESR and CRP in multidrug-resistant tuberculosis patients

The emergence of multidrug-resistant tuberculosis (MDR-TB) is bringing new challenges. MDR-TB is caused by Mycobacterium tuberculosis (M. tuberculosis) that is resistant to isoniazid and rifampicin, with or without resistance to other anti-tuberculosis drugs. Approximately 450,000 people developed MDR-TB worldwide in 2012 and an estimated 170,000 people died from the disease [1] . Bacterial burden is not strictly correlated with disease progression, and several hallmarks of severe tuberculosis suggest that insufficiently controlled inflammation plays an important role in pathogenesis [2] . It has been reported that nucleotide-binding and oligomerization domain (NOD) like receptor 3 (NLRP3) inflammasome and its cytokines IL-1b and IL-18 play a critical role in host defense and immunopathologic process in chronic M. tuberculosis infection in vitro and in animal models [3-5] . However, little is known about the role of NLRP3 inflammasome and IL-1b and IL-18 in MDRTB patients. We determined serum IL-1b and IL-18 contents in drug-susceptible tuberculosis (DS-TB) and MDR-TB patients and investigated their relationships with disease severity in tuberculosis. Written informed consent was obtained from all study participants, and the study was approved by the Research Ethics Committee of Nanjing Medical University (Nanjing, China). TB patients were recruited from Nanjing Thoracic Hospital from January to December 2014 as a subset of a multi-center study. The baseline characteristics of 30 healthy control subjects, 35 DS-TB patients, and 30 MDR-TB patients are summarized in Table 1. MDR-TB patients had more severe radiographic features than DS-TB patients (P50.01). Serum ESR and CRP levels were significantly higher in TB patients than in healthy controls, and in MDR-TB patients than in DS-TB patients. ELISA showed (Fig. 1A) that the levels of IL-1b in MDR-TB (7.48¡3.58) were significantly higher than that in DS-TB patients (3.07¡2.26). Meanwhile, serum IL-18 displayed the same trend, which was higher in MDR-TB patients (131.03¡94.92) than DS-TB patients (94.28¡57.10) and healthy controls (61.66¡24.78) (Fig. 1B). To investigate whether serum IL-1b and IL18 are related to radiographic severity, we stratified TB patients according to unilateral and bilateral lesions. In DS-TB patients, IL-1b (Fig. 1C) and IL-18 (Fig. 1D) were significantly higher in patients with bilateral lesion