Submitted to: Animal Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 2005
Publication Date: November 2, 2005
Citation: Kogut, M.H., He, H., Kaiser, P. 2005. Lipopolysaccahride-binding protein/CD14/TLR4-dependent recognition of Salmonella LPS induces the functional activation of chicken heterophils and up-regulation of pro-inflammatory cytokine and chemokine gene expression in cells. Animal Biotechnology. 16:165-181. Interpretive Summary: White blood cells of the immune system in chickens must be able to “see” bacteria when they invade the body. One type of immune cell that we are studying in the chicken is called the heterophil. The heterophil is the first immune cell that bacteria come in contact with when it invades the body. The purpose of this research was to look for the way the heterophil sees Salmonella and then what happens when the heterophil sees the bacteria. We found that the heterophil has 2 structures on its surface that are required to work together to see the bacteria. Once the bacteria are seen, the heterophil then produces a series of chemicals that calls other heterophils and immune cells to the site where the bacteria is invading. These cells can then prevent a serious infection. This research is important to vaccine manufacturers because it will help them make vaccines against Salmonella that will help the immune cells “see” the bacteria better, and thus, help the chicken get rid of the bacteria quicker.
Technical Abstract: Lipopolysaccharide (LPS) is the major pathogen-associated molecular pattern (PAMP) found in the cell wall of gram-negative bacteria and, in mammals, is recognized by the Toll-like receptor 4 (TLR4) in conjunction with the serum protein, lipopolysaccharide-binding protein (LBP), and the CD14 co-receptor. We have found that chicken heterophils constitutively express multiple TLRs including TLR4. Interestingly, ultra-pure LPS from Salmonella minnesota, directly induced the functional activation of heterophils without the presence of LBP. However, the role of LBP and CD14 in the recognition of LPS and the induction of innate immunity, including cell functional activation and the transcription of cytokine and chemokine genes in chicken heterophils, is not known. As previously seen, in the absence of chicken serum, heterophil exposure to ultra-pure LPS from Salmonella minnesota stimulated an increased degranulation response. However, the presence of 5% chicken serum, presumed to be a source of LBP, increased heterophil degranulation by 84%. In addition, the presence of either soluble recombinant human LBP (rhLBP, 68%) or CD14 (39%) also induced the up-regulation of the heterophil degranulation response. Incubation of heterophils with either chicken serum or rhLBP also significantly induced the up-regulation of pro-inflammatory cytokine (IL-1beta, IL-6, and IL-18) and chemokine (CCLi4, CXCLi1, CXCLi2, and the CXC receptor 1) mRNA expression. Moreover, polyclonal antibodies directed against rat CD14 and human TLR4, but not antibodies against human TLR2, blocked LPS-mediated degranulation and up-regulation of the pro-inflammatory cytokine and chemokine mRNA expression. These data clearly demonstrate that LBP and CD14/TLR4 engagement is directly involved in LPS-mediated functional activation and innate immune gene expression in chicken heterophils.