Submitted to: Developmental and Comparative Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/12/2004
Publication Date: 1/15/2005
Citation: He, H., Lowry, V.K., Ferro, P.J., Kogut, M.H. 2005. CpG-oligodeoxynucleotide-stimulated chicken heterophil degranulation is serum cofactor and cell surface receptor dependent. Developmental and Comparative Immunology. 29:255-264. Interpretive Summary: DNA is a genetic blueprint of life and occurs in all cells. DNA found in bacteria contains a unique element, called CpG-DNA. Through a process called degranulation, certain chicken white blood cells called heterophils produce chemicals that can kill bacteria. This bacteria-killing mechanism helps chickens fight bacterial infections. Chicken heterophils were found to produce bacteria-killing chemicals when they are exposed to CpG-DNA, but we have found that the degranulation process needs help from molecules in chicken blood serum. Our findings are important to the pharmaceutical industry in the United States because it shows that we can possibly use chemicals to stimulate heterophils in baby chickens to fight different bacterial infections.
Technical Abstract: Synthetic oligodeoxynucleotide containing unmethylated CpG motif (CpG-ODN) is stimulatory to chicken heterophils. Recognition of CpG-ODN by chicken heterophils leads to the mobilization and release of granules. This CpG-ODN-induced heterophil degranulation was serum-dependent. Removal of chicken serum (CS) rendered heterophils unresponsive to CpG-ODN stimulation. In the presence of CS, CpG-ODN stimulated a dose-dependent degranulation of heterophils. Heat-denaturation and membrane filtration of CS revealed that the active serum cofactor(s) was most likely a protein in nature with a molecule mass within 50 to 100 kDa. This serum cofactor(s) was heat-resistant at 56ºC for 1 hr. The involvement of a cell surface receptor in recognition of CpG-ODN was demonstrated by the following: (1) trypsin treatment of the heterophils abrogated the degranulation response and (2) CpG-ODN-induced heterophil degranulation was sensitive to the inhibition of Clathrin-dependent endocytosis. In addition, among various microbial agonists, including CpG-ODN, lipopolysaccharide (LPS), lipoteichoic acid (LTA), phorbol myristate acetate (PMA), and formalin-killed Salmonella enteritidis, CpG-ODN was the only agonist that displayed serum-dependent induction of degranulation in chicken heterophils. This is the first report that shows serum-dependent activation of leukocytes by CpG-ODN.