Amiel G. Cooper

Scanning electron microscopy of human T-cell and B-cell rosettes.

Abstract The surface of human lymphocytes was studied by scanning electron microscopy. Lymphocytes from peripheral blood or tonsils were identified as thymus-derived (T) cells or thymus-independent (B) cells by virtue of the ability of T cells to form rosettes with sheep red cells and for some B cells to form rosettes with complement-coated human red blood cells. The rosettes were gluteraldehyde fixed and subsequently examined by scanning electron microscopy. Lymphocytes, both rosetting and non-rosetting, had multiple surface microvilli. As compared to rosetting B cells, rosetting T cells were generally smaller and smoother, with fewer and shorter microvilli. Microvilli appeared to be the sole cell-cell contact point between T cells and sheep red blood cells; B cells made contact through both villous and non-villous areas. Microvilli are an important mode of primary contact between lymphocytes and the outside world. (N Engl J Med 289:548–551, 1973)

Further characterization of the glycoproteins and glycosaminoglycans released from TA3 murine adenocarcinoma cells in culture

TA3 murine ascites adenocarcinoma cells were compared for their ability to release radioactive glucosamine and 35SO4-labeled glycoproteins and glycosaminoglycans into the culture medium. Both TA3-Ha and TA3-St cells contained cell-surface heparan sulfate that was released into culture, but not chondroitin sulfate. Both cells released a membranous aggregate of labeled components from the cell surface and hyaluronic acid from inside the cells that fractionated in the void volume of Sepharose CL-4B. This void-volume fraction from the TA3-Ha cells contained glucosamine-labeled epiglycanin at a higher concentration relative to other glucosamine-labeled components than that found on plasma membranes. Glycoproteins associated with epiglycanin found on the cell surface, as well as released into culture medium, contained sulfate that could not be removed by chondroitinase ABC, heparinase, or keratinase. Kinetic analysis of the glucosamine-labeled material released from TA3-Ha cells indicated that hyaluronic acid was released rapidly with a 45-min half-life, whereas the other membranous components were released much more slowly.