The Effects Of LPS On The Expression Of TLR4in Chicken Trachea And Lung

The respiratory system is exposed to a variety of exogenous antigens in the air because of its relatively open characteristics, so the respiratory system not only plays the role of gas exchange, but also plays an important role in the immune defense. The host firstly activates the innate immune reactions recognizing the antigens by pattern recognition receptors (PRRs), and causes a series of immune effects to defense against the invaded pathogens or foreign antigens. Toll like receptors (TLRs), as one kind of pattern recognition receptors, are distributed in many tissues, linking the innate and acquired immunity. TLR4is considered to play an important role in resistance to gram negative bacteria. The incidence of bacterial respiratory disease showed a rising trend in poultry. The reports about the role of TLR4in chicken respiratory system in the immune response are rare. In the study, in order to explore the effects of LPS stimulation on the poultry respiratory system and the function of TLR4in respiratory diseases, the immunohistochemical staining, cell specific staining and ELISA were used to explore the histological structure changes and the distribution of TLR4expression in the chick trachea and lung in the case of LPS stimulation. The main results are as follows:1The effects of LPS stimulates on the histological structure of chick trachea The sections of chick trachea show that the epithelium is pseudostratified ciliated columnar epithelium mixed with ciliated columnar cells and goblet cells. There are rare tracheal glands in chick tracheal submucosa in the groups of control and LPS. The hyaline cartilage ring is not complete disc in1week old chicks. There often have two layers of cartilage in cartilage slice junction. It is showing that parts of the epithelial cells are arranged loosely, the histological structure of the cells is fuzzy and there is cilium desquamating in some columnar ciliated cells at36h and72h after LPS stimulation. The number of goblet cells in epithelium reduces after12h of LPS stimulation; at36h and72h of stimulation, the number increases slightly compared with that at12h, but it is still less than that in control group(P<0.05). The results suggest that LPS can lead to injury of chick trachea.2The effects of LPS stimulates on the expression of TLR4in chick tracheaIn order to observe the distribution of TLR4expression in chick trachea we used the immunohistochemical staining method. The results show that TLR4is observed in all groups. The protein of TLR4mostly expressed on the apical cell surface of ciliated columnar cells and also found in the submucosa. There is no expression of TLR4in goblet cells. The expression of TLR4increased in the trachea after LPS stimulation and peaked at36h. The changes of TLR4expression after LPS stimulation indicate that the TLR4may mediate tracheal epithelial cells in response to the invaded pathogens.3The effects of LPS stimulates on the histological structure of chick lungIt was observed that the chick lung is composed of many pulmonary lobules and there are connective tissues among pulmonary lobules. The tertiary bronchus is in the central of pulmonary lobule. It is the openings of pulmonary atrium around the the tertiary bronchus lumen. There are the smooth muscle bundles around the ostial pulmonary atrium. The pulmonary atrium is cystoid and the epithelial layer is simple squamous epithelium, which wrapped around the elastic fibers. The pulmonary capillary epithelium is simple squamous epithelium, which wrapped around the reticular fibers and capillaries but with no the elastic fibers.At12h and36h of LPS stimulation, there is vague boundary between parts of pulmonary lobules; the lumen of pulmonary atrium becomes narrow or even disappears; the plumonary capillary cells become crowded together; therer are large number of red blood cell distribution in parts of tertiary bronchus, pulmonary capillary and blood vessels; scattered white cells are distributed in the pulmonary desmohemoblast. At72h of LPS stimulation, the histological structure of chick lung has becomed normal compared with that of groups12h and36h. The results show that the LPS of intraperitoneal injection can cause lung injury and inflammation.4The effects of LPS stimulates on the expression of TLR4in chick lung In order to observe the distribution of TLR4expression in chicks lung are used the immunohistochemical staining method. The results show that TLR4is observed in all groups. TLR4prominently expressed on the cells which in pulmonary desmohemoblast and blood vessels. It is found that the positive cells of TLR4in lung possibly are plasma cells, monocytes or macrophages, lymphocytes or heterophils dyeing with HE staining, Schiff-methylene blue staining and immunohistochemical staining on serial section. The expression of TLR4rises in the chicks lung at12h and36h after injection with LPS and reduces at72h (P<0.05). The distribution of TLR4expression in chick lung prompts that TLR4on macrophages, heterophils, and lymphocyte can mediate the activation of the cells, causing inflammation reactions to play a defensive role against the invaded pathogens.5The effects of LPS stimulates on the expression of SIgA in chicken trachea and lungThe ELISA results showed that the expression of the secretory IgA (SIgA) in the chick trachea increases at12h and36h and reduces at72h after the LPS stimulation. The expression of SIgA is the highest at12h. But the changes expression of SIgA in the chicks lung is not obvious(P>0.05). The results indicate that the SIgA in tracheal mucosa may be involved in the response to LPS stimulation and mainly play a role in early stage.