Monocytes from children with clinically stable cystic fibrosis show enhanced expression of Toll-like receptor 4

Lung disease in patients with cystic fibrosis (CF) is characterized by recurrent bacterial respiratory infections and intense airway inflammation. Pattern recognition receptors such as Toll-like receptor 2 (TLR2) and TLR4 identify bacterial pathogens and activate the innate immune response. We therefore hypothesized that increased expression of these receptors would be found on circulating immune cells from children with CF. A cohort of 66 young children (median age 3 years) with CF was studied and compared to both healthy controls (n = 14) and children without CF who were being investigated for recurrent respiratory infections (non-CF disease controls; n = 17) of a similar age. Surface expression of TLR2 and TLR4 on peripheral blood monocytes was analyzed using flow cytometry. TLR4 expression was significantly higher in patients with CF compared to healthy controls (P=0.017) and non-CF disease controls (P=0.025) but did not vary according to the presence or absence of pulmonary infection with Gram-negative or Gram-positive bacteria (P=0.387) in the CF group. In contrast, TLR2 expression was similar across all three study groups (P=0.930). The increased surface expression of TLR4 seen in young children with CF appears to be related to having CF per se and not related to current pulmonary infection. Pediatr Pulmonol. 2010; 45:883-889. (C) 2010 Wiley-Liss, Inc.