Abstract
The cholera toxin-colloidal gold-labeled IgG-F(ab')2 anti-cholera toxin ultrastructural immunocytochemical procedure has been used for the localization of GM1 monosialogangliosides on the surface of human bone marrow cells. The number of gold particles per micron of cell surface was counted and the data subjected to statistical analysis. Cholera toxin (CT) binding characteristics assessed in several subjects showed consistent labeling patterns for the various types of marrow cells, although minor quantitative differences were noted in surface labeling densities between subjects. Surface labeling was nonuniformly distributed along the cell membrane of the marrow cells and label clusters or domains were commonly noted. Data analysis indicated that CT labeling was related to cell type, to cell lineage, and to the stage of maturation. Mature neutrophils were the most reactive of the marrow cells and the CT labeling of this cell series increased stepwise from the promyelocyte stage to the segmented neutrophil. A similar pattern occurred during eosinophil maturation and the maturation of the monocyte. A different labeling pattern was found during the differentiation of the erythrocytic cell series with low labeling of proerythroblasts increasing modestly to the early normoblast stage and then decreasing during the final phase of maturation. Exposure to neuraminidase prior to the immunocytochemical sequence induced a major increase in surface CT labeling of the various types of marrow cells, as was particularly evident for the platelet, promyelocyte, myelocyte, monocyte, promonocyte, and erythrocyte cell groups. The data indicated that the number of cryptic GM1 and/or higher gangliosides exposed by neuraminidase in the cell membrane varied during cell differentiation and was directly related to specific cell types. Exogenous GM1 also was demonstrated to be incorporated into the surface of the bone marrow cells in a differential manner and the extent of incorporation was found to be related to specific cell types and to their stage of maturation.