Cellular defense of the avian respiratory system. Influx of phagocytes: elicitation versus activation.

We studied various means of inducing avian phagocytes to migrate to the respiratory tract. No significant and consistent increases in the number of avian respiratory phagocytes (ARP) were elicited by intravenous inoculation with Escherichia coli lipopolysaccharide (LPS), Saccharomyces cerevisiae glucan (G), and Freund's incomplete adjuvant (FIA) in a water-in-oil-in-water emulsion; subcutaneous inoculation with the LPS-G-FIA homogenate; or aerosolized exposure to LPS-G-FIA, thioglycolate, and proteose-peptone. Intravenous inoculation with heat-killed Corynebacterium parvum resulted in a significant increase in the number of ARP by day 6 after inoculation; intratracheal inoculation of C. parvum effected a more rapid and higher level of phagocyte migration to the respiratory tract. Intratracheally administered E. coli induced significant migration of phagocytes to the respiratory system so that by 24 hours postinoculation, the group average number of ARP was about 50-100 times as high as the number in unstimulated control birds. None of the birds yielding high numbers of phagocytes from their respiratory tract had signs of respiratory disease.