Cellular defense of the avian respiratory tract: paucity of free-residing macrophages in the normal chicken.

Avian respiratory macrophages (ARM) were obtained from lungs and air sacs of 122 White Plymouth Rock chickens, ranging from 376 to 3800 g in weight. Procedures involved lavaging through the surgically prepared trachea with either a 15-g cannula or French #8 pediatric urinary catheters. Factors, in different combinations, investigated for their effects on the ARM yield, were: lavage fluids (0.85% physiologic saline, 0.1 M phosphate-buffered saline, Ca-Mg-free Hanks' solution, Eagle's minimum essential medium); additives (10 U heparin/ml, 0.1% EDTA, 12 mM lidocaine); lavage repetitions (from 3 to 10); fluid temperature (room and 41 C); and lavage time (fluid retention up to 35 min). None of the lavage methods emerged clearly as the best, with phosphate-buffered saline and 0.85% physiologic saline alone as good as when combined with additives. Although 10 lavages yielded more ARM, it appeared that the majority of ARM washed off into the early lavages. Chickens from a line selected for large body size had more ARM than those from a line selected for small body weight. Regardless of genetic line, however, the chickens yielded a very low number of ARM compared with mammalian species of the same or smaller weight. Most of the birds yielded only 200,000 to 300,000 ARM, with minimum yields being less than 10,000, the maximum being 2 million ARM. Either these results point to a deficiency in the defense system of the chicken's respiratory tract against bacteria, mycoplasma, fungi, and viruses, or mechanisms other than macrophages are primary in resistance to pathogens.(ABSTRACT TRUNCATED AT 250 WORDS)