Nonspecific cellular defense of the avian respiratory system: a review.
The normal, steady-state, avian respiratory system has very low numbers of residing avian respiratory phagocytes (ARP). Birds must rely heavily on the influx of ARP to defend against infectious agents. The system is refractory to elicitation by inert stimulants, but responds efficiently to replicating bacteria, with very rapid influx of large numbers of activated ARP (polymorphonuclear neutrophils, heterophils, and macrophages) with increased phagocytic proportions and capacities. The numbers subside within a few a days. Activated ARP act in a non agent-specific manner: Pasteurella multocida-activated ARP can defend against a severe Escherichia coli airsacculitis. Parenteral routes of stimulation generally are not, respiratory routes are very, efficient in activating ARP. Heterophils are the most efficient in defensive reactions, such as oxidative burst, production of nitric oxide and killing of bacteria. Respiratory viruses may stimulate, but also may diminish some of the defensive functions of ARP. This is also true for attenuated, modified live virus vaccines. These vaccines must be used carefully in the presence of subclinical bacterial, mycoplasmal infections. Published literature on non-specific cellular defense of the avian respiratory system is very limited, particularly about interactions among multiple infectious agents and the system.
Toth
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Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA. ttoth@vt.edu
D000818:Animals; D001715:Bird Diseases / Q000276:immunology* / Q000382:microbiology / Q000517:prevention & control / Q000821:virology; D010586:Phagocytes / Q000276:immunology*; D012140:Respiratory Tract Diseases / Q000276:immunology* / Q000382:microbiology / Q000662:veterinary* / Q000821:virology