Serum level of cathelicidin LL-37 in patients with active tuberculosis and other infectious diseases.

A growing body of evidence indicates the role of cathelicidin LL-37, a member of the antimicrobial peptide family, in host innate defense mechanisms. The important role of this peptide in infectious diseases is also suggested, however, to date, data relating to LL-37 expression in the course of bacterial infections are far from complete. Therefore, the aim of the present study was to determine LL-37 serum levels in adult patients with pulmonary tuberculosis (TB). For comparison, circulating LL-37 levels in patients with pneumonia induced by Gram-positive or Gram-negative bacteria species and in healthy subjects were evaluated. Fifty patients with pulmonary TB, 31 patients with pneumonia caused by gram-positive bacteria, 68 individuals with pneumonia caused by Gram-negative bacteria, and 61 randomly selected healthy subjects were enrolled in the study. Serum LL-37 concentration was measured using an enzyme-linked immunosorbent assay (ELISA). We established that the mean level of LL-37 was statistically significantly higher in TB patients than that in patients with Gram-positive bacteria-induced pneumonia (p < 0.001), in patients with Gram-negative bacteria-induced pneumonia (p < 0.001), and in healthy controls (p < 0.001). In patients with TB, no statistically significant correlations between serum LL-37 and CRP concentrations (r = -0.2042; p = 0.189) and between serum LL-37 concentration and WBC count (r = -0.1277; p = 0.414) were observed. Our observations clearly documented that cathelicidin LL-37 plays a role in defense mechanisms against infectious agents, and is particularly important when the infection is caused by an intracellular pathogen.