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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.

Proteomics analysis of bovine bronchoalveolar fluid (BAF) following induction of pneumonia with Mannheimia haemolytica using nanoflow liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS) resulted in the identification of 88 unique proteins. Proteins detected in BAF included antimicrobial peptides (AMPs), complement factors, acute-phase proteins, protease inhibitors, and proteins involved in oxidation-reduction. Notwithstanding biological variation, differences in relative protein abundance, determined using normalized peptide counts, were detected for select proteins in BAF from genuinely infected versus sham-infected animals. To demonstrate the applicability of using normalized peptide counts to assess protein expression trends, LC-MS/MS data for the acute-phase protein haptoglobin (HPT) were compared with ELISA data, and statistical evaluation of the relationship between the data revealed a strong measure of association. Differences were detected between sham- and genuinely infected animals for haptoglobin, as well as the AMPs cathelicidin-1 and cathelicidin-4, and inter-α-trypsin inhibitor heavy chain-4, a fairly novel protein involved in the acute phase response. Though the small sample size limited the scope of the inferences, the results indicate the likely importance of AMPs and acute-phase proteins during respiratory infection, and provide additional information regarding potential mechanisms involved in the bovine mucosal barrier defense., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)