Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 19, 2002
Publication Date: April 1, 2003
Interpretive Summary: Baby chickens have a poorly functioning immune system during the first week of life, and are at risk for many diseases. The objective of this experiment was to look at how a group of white blood cells, heterophils, react to bacteria that cause disease in baby chickens. We found that heterophils use specific bacteria recognition points on their membranes to identify and initiate the process of ridding the chicken of bacteria. The results of this experiment are important to the pharmaceutical and agricultural industries in the United States because these receptors could be used to stimulate heterophils in baby chickens to be more efficient at removing disease causing organisms. Antibiotics are becoming less useful and their use has become more restricted in human and animal medicine. It is the hope of the authors that this research may one day be used to bolster the baby chicken's immune system without the use of antibiotics.
Technical Abstract: Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS) and lipoteichoic acid (LTA), which are found in the cell walls of gram negative and gram-positive bacteria, respectively. This study was conducted to determine if TLRs are present on chicken heterophils and to determine if these receptors mediate oxidative burst. Heterophils isolated from neonatal chicks were exposed to gram-negative Salmonella enteritidis (SE), gram-positive Staphylococcus aureus (SA), SE-LPS, and SA-LTA and the oxidative burst quantitated by luminol-dependent-chemiluminescence (LDCL). SE, SA, SE-LPS, and SA-LTA stimulated a significant increase in oxidative burst from heterophils. Furthermore, we measured the inhibitory effects of polyclonal antibodies to rat CD14, human TLR2 and TLR4 on the oxidative burst of heterophils when stimulated with LPS and LTA. The data suggest that TLR2 and TLR4 mediate LPS-stimulated oxidative burst while CD14 and TLR2 mediate LTA-stimulated oxidative burst in heterophils. This is the first report of PAMPs from gram-positive and gram-negative bacteria interacting with TLRs of avian heterophils.