Cathelicidin and human β-defensin 2 in bronchoalveolar lavage fluid of children with pulmonary tuberculosis.

BACKGROUND: The antimicrobial peptide cathelicidin LL-37/hCAP-18 and human β-defensins (hBD) are key factors in innate immune responses of the respiratory tract. OBJECTIVE: To determine LL-37 and hBD-2 concentrations in the bronchoalveolar lavage (BAL) fluid of paediatric patients (aged <16 years) with pulmonary tuberculosis (TB) and to compare these with concentrations in healthy children. METHODS: We measured peptide concentrations using an immunosorbent assay (ELISA). RESULTS Forty TB patients and 40 healthy controls were enrolled in the study (mean age 9.2 ± 4.7 and 8.3 ± 4.2 years, respectively, P = 0.97). The two groups exhibited no statistically significant difference in terms of sex, body mass index, relative weight or 25-hydroxyvitamin D levels. The mean BAL LL-37 level of the TB group was significantly higher than that of the control group (0.95 ± standard deviation [SD] 1.33 vs. 0.35 ± SD 0.51 ng/ml, P = 0.01, t = 2.54). The hBD-2 level was also higher in the TB group; however, the difference was not statistically significant (0.30 ± SD 0.58 vs. 0.14 ± SD 0.30 ng/ml, P = 0.11). There was no correlation between LL-37, hBD-2 and 25-hydroxyvitamin D levels. CONCLUSIONS Our data suggest that LL-37 and hBD-2 may play an important role in TB pathogenesis in children. To our knowledge, this is the first study on BAL LL-37 and hBD-2 concentrations in children with pulmonary TB.