A comparative in vitro study of morphology and phagocytic capacity of the free surface respiratory macrophages in the duck and the rabbit
Quantitative and qualitative characteristics of the free surface respiratory macrophages (SM) of the domestic duck ( Anas platyrhynchos ) were compared with those of the domestic rabbit ( Oryctologus cuniculus ) under similar experimental conditions. The duck h ad significantly fewer SM compared to those of rabbit. In the duck, there was flux of SM as depicted by increase of SM during the first thre e progressive lavages before the number started to de cline during the fourth and fifth lavages. In the rabbits, there was decline in number of the SM duri ng the five progressive lavages. Morphologically, t he cells were similar at light and electron microscopy levels. Ultra structurally, the SM had filopodial extensions and variable vesicular cytoplasmic bodie s. The diameters were comparable with duck SM mean diameter measuring about 12 μm while that of t he rabbit SM mean diameter being 13 μm. The mean volume density of polystyrene particles ingest ed by the SM, that is volume of particles per unit volume of SM, revealed that the duck SM had signifi cantly higher mean phagocytic capacity at 20% than rabbit SM whose mean phagocytic capacity was 9%. Th e assertion that domestic birds are prone to respiratory diseases due to dearth of SM alone may not be true. The higher phagocytic capacity observed in the duck SM probably compensates for th e few resident SM. Vulnerability to respiratory diseases by the domestic birds may be due to other factors such as poor husbandry and management strategies and, severe genetic manipulations for fa st growth and productivity that may have weakened cellular immunological defenses.