Ultrastructural and cytochemical studies in normal Japanese quail (Coturnix coturnix japonica) eosinophils and in those from birds with experimentally induced eosinophilia

Normal eosinophil development in the Japanese quail (Coturnix coturnix japonica) was similar to that described in the fowl and the duck, with granulogenesis occurring in the Golgi apparatus. The characteristic lipid droplets were small in the immature eosinophils, and after staining specifically for lipid, small moieties were also traced to the Golgi apparatus. In mature eosinophils the lipid droplets measured between 1.0 and 1.5 micron in diameter and they were surrounded by profiles of smooth endoplasmic reticulum. Eosinophilia was difficult to induce in quails; injections of either horse serum or bovine serum albumin (BSA)/aluminium hydroxide produced a poor response. In some quails in which eosinophilia was produced, however, eosinophil granules showed many crescentic and vacuolated forms. The lipid droplets in the activated eosinophils were fused in many cells to form large intracellular aggregates of lipid. Quail eosinophils, which hitherto have been regarded as peroxidase-negative, had strong activity in the lipid droplets of cells from stimulated birds. It is postulated that this peroxidase-positive reaction may represent a form of ceroid or lipofuscin pigment resulting from lipid peroxidation. Acid phosphatase and trimetaphosphatase reactions were reduced in many activated cells, with a large proportion of granules being non-reactive. The results of dietary manipulations in quails appear to suggest that in stressful situations the eosinophil metabolism is altered and there is a reduction in the number of lipid droplets in the cell.