The ratio of full length IgY to truncated IgY in immune complexes affects macrophage phagocytosis and the acute phase response of mallard ducks (Anas platyrhynchos).

Ducks produce a full length IgY and a truncated isoform (IgYDeltaFc). IgY and IgY(DeltaFc) were isolated from ducks vaccinated against Escherichia coli and used to make E.coli-Ig immune complexes (IC). Phagocytosis of IC by duck monocytes decreased directly with the proportion of IgYDeltaFc (p<0.001). IC containing IgY:IgY(DeltaFc) at ratios of 100:0, 50:50, 0:100, and 0:0 (E. coli alone) were injected intravenously into naïve mallard ducks. At 24 h after injection, plasma hemopexin levels were higher in ducks given either the 0:100 ratio or the 100:0 ratio than those given 50:50 or E. coli alone (p<0.005) Liver IL-1beta mRNA levels followed a similar pattern. Splenic IL-1beta mRNA decreased markedly as the proportion of IgY(DeltaFc) increased (p<0.01) Thus, IgY(DeltaFc) may shift the response to IC from the spleen to the liver as infections progress from acute to chronic.