Some of the mechanisms by that endotoxin can mediate its effects include neutrophil and eosinophil recruitment as well as the activation of macrophages [3, 5, 6]. Chemically, endotoxins consist of lipopolysaccharides (LPS) that exert their effects via the CD14 receptor, a 53-kDa surface glycoprotein [7] expressed on monocytes, macrophages, granulocytes and B lymphocytes [5, 6]. The molecular

interactions underlying the binding of LPS have been extensively studied in recent years. Accordingly, LPS-binding protein (LBP) facilitates the binding of LPS in combination with CD14 to a receptor complex, which consists Selleckchem HM781-36B of Toll-like receptor-4 (TLR-4) and MD-2 [8–10]. The activation of the TLR induces an intracellular

signalling cascade, which results in the release of cytokines such as interleukin (IL)-6, IL-8 and tumour necrosis factor (TNF)-α [6, 11] which have also been shown in elevated concentrations in asthma [12–14]. In vitro, CD14 is constitutively released from mononuclear cell cultures as soluble CD14 (sCD14) [15, 16]. sCD14 can be found in two isoforms, a 49- and a 55-kDa protein. The 55-kDa isoform is produced by a shedding mechanism while the 49-kDa form is thought to derive from the interstitial space [16, 17]. The 49-kDa isoform is found in healthy subjects and is significantly elevated in patients with Cisplatin purchase sepsis [18], polytrauma [19] and atopic dermatitis [20]. Shedding is increased by LPS and TNF-αin vitro [21] and also in vivo [22]. The much function

of sCD14 has been associated with the activation of cells which do not possess membrane-bound CD14 [8]. Elevated levels of sCD14 have been found in bronchoalveolar lavage in several diseases such as tuberculosis, sarcoidosis, allergic alveolitis and idiopathic pulmonary fibrosis [6, 23–27]. sCD14 also seems to play a role in allergic asthma. Dubin et al. [28] showed an increase in sCD14 in bronchoalveolar lavage fluid (BALF) 24 h after allergen provocation which was confirmed by others [29]. Increased concentrations were also found in children with status asthmaticus [30]. In addition, CD14 expression has been correlated to the influx of neutrophils into the airways [22]. It has been suggested that this might be related to a remodelling processes in the airways as has been shown in an animal model with endotoxin-sensitive mice [31]. Moreover, distinct gene-polymorphisms of the C14 gene have been associated with an increased risk to develop an atopic phenotype [32]. It can therefore be hypothesized that an elevated expression of the LPS receptor might be involved in the activation of the inflammatory cascade in asthma which could lead to chronic inflammation, remodelling of the airways and subsequently an accelerated loss in FEV1.