Effects of germ-free environment, bursectomy and irradiation on the production of natural and immune opsonins in young chicks.

The opsonins for goat erythrocytes present in the circulation of normal chicks after the decline of maternal antibody may be natural antibodies. Natural antibodies for goat erythrocytes are detectable in normal chick serum from 7 days of age. However, various immunosuppressive treatments in earlier life failed to depress the level of opsonins for goat erythrocytes during the first 2 weeks of age. A germ-free environment did not affect phagocytosis. The slower clearance of goat erythrocytes from the circulation of chemically bursectomized or irradiated chicks was in proportion to the degree of runting. Weight-adjusted doses of goat cells given to such runted chicks were cleared at the same rate as larger doses in control birds. No specific suppression of opsonin level occurred in the absence of runting. Although the production of immune antibody was depressed by bursectomy in older chicks or by irradiation of 19-day-old embryos immunized in mid-embryonic life, there was no such inhibition of the production of natural opsonins.