Fine structural and cytochemical studies of eosinophils from fowls and ducks with eosinophilia.

The ultrastructure and cytochemistry of eosinophils from adult fowl and ducks with either spontaneous or experimentally induced eosinophilia were examined. The results showed that a high proportion of the eosinophils in the peripheral blood of eosinophilic birds had ultrastructural features different from those of normal eosinophils. In both species, there was a reduction in cell size. Fowl eosinophil granules showed similar morphological changes to those seen in the quail with many crescentic and vacuolated forms being present. In eosinophilic ducks, the crystalline interna of the specific granules were often fragmented or were either partially or completely lysed. Cytochemically, peroxidase activity in both species was generally unaltered in abnormal eosinophils compared with those from normal birds. This correlates with the findings in man. However, amounts of acid phosphatase and trimetaphosphatase were reduced in many cells, with a large proportion of granules being non-reactive. The latter observation corresponds with that in quail but differs from man, in which stimulated eosinophils have increased enzymatic activity.