Alkaline Phosphatase in the Developing Bursa of Fabricius.

Abstract

The ontogeny of alkaline phosphatase in the bursa of Fabricius was studied by histochemical and biochemical methods [in chick embryos]. The activity of alkaline phosphatase increased from days 11-17 of incubation, i.e., during the time of the lymphoid follicle formation in the developing bursa. The activity was localized in the mesenchymal tissue surrounding the lymphoid follicles. Testosterone given in ovo prevented the appearance of alkaline phosphatase in the bursal mesenchyme but had no effect on the activity of the embryonic liver. In ovo treatment with cyclophosphamide had no effect on the alkaline phosphatase in the bursa. By using transplantation of embryonic bursal stem cells, in contrast to cyclophosphamide, testosterone destroyed the capacity of the bursa to serve as a differentiation site for the B[bursa-derived]-cell lineage. Testosterone affected the stromal cells of the bursa, while cyclophosphamide destroyed only the lymphoid population undergoing differentiation and left the bursal stroma intact.