Ultrastructure of resting and rh-GMCSF-treated human macrophages derived from blood monocytes

The ultrastructure of cultured blood monocyte-derived human macrophages was investigated and correlated under the effect of different doses of rh-GMCSF (dose 1 = 25 IU/ml, dose 2 = 125 IU/ml and dose 3 = 250 IU/ml). Resting macrophages showed irregular cell borders and pseudopodia pushed out in all directions. Their cytoplasm depicted rough endoplasmic reticulum and Golgi complex in the perinuclear area. Lipid globules, primary lysosomes and mitochondria were characteristically prominent. rh-GMCSF-stimulated macrophages were more voluminous and their nuclei were irregular in outline, with predominance of euochromatin over heterochromatin. The cytoplasm was overcrowded by an increasing number of organelles including lysosomes, phagolysosomes and mitochondria. Golgi complex demonstrated a wide-spread distribution along the cells, with profound membrane expansion and cisternal dilatation; especially, in cells treated with dose 2. Electron dense osmiophilic deposits (collapsed membranes) were seen in association with lipid globules, which were commonly polarized at cell peripheries. Most of these changes were dose dependent. However, cells treated with dose 3 manifested additionally well-developed centrioles, inapparent nuclear membrane, display of microfilaments and well-established adhesions. The demonstrated ultrastructural changes in rh-GMCSF-treated human macrophages indicated pronounced activation, which supports the reported clinical effect of this cytokine.