Isolation, culture, and preliminary characterization of ellipsoids (sheathed capillaries of Schweigger-Seidel) of the pig spleen. II. An enzyme histochemical study of in vitro cultivated ellipsoids.

Whole isolated ellipsoids (sheathed capillaries of Schweiger-Seidel) of the pig spleen were explanted in Medium 199 containing 20% fetal calf serum or horse serum respectively. Cultures were kept in a gas phase of 5% carbon dioxide in air at 37 degrees C. After about 4 days in culture the outgrowth of two morphologically different cell types was apparent. Small cells of fusiform or stellate morphology displayed high activity of acid phosphatase. N-acetyl-beta-glucosaminidase and beta-glucuronidase activity were also detectable. Furthermore these cells were highly reactive for unspecific esterase and gamma-glutamyl transpeptidase activity. Endogenous peroxidase activity was present in the cytoplasm and in the perinuclear space. Stellate cells therefore are thought of as ellipsoid macrophages. Additional observations reported are the expression of Fc-receptors on stellate cells. They triggered the phagocytosis of opsonized test particles. The second cell type showed fibroblastic morphology. The large well spread cells did exhibit low activities of acid phosphatase and N-acetyl-beta-glucosaminidase. The other enzyme activities examined were not detectable. The nature of these cells is not well understood at present. Most likely they are constituents of the framework of the ellipsoids. No transitions between stellate cells and fibroblastic cells were found.