Nineteen lines of human fibroblasts were inoculated with a filtrate prepared from the ST feline sarcoma. Seven lines showed morphological alteration and released focus-forming activity for feline cells, 2 lines showed morphological alteration but did not release focus-forming activity, and 11 lines showed no morphological alteration and released no focus-forming agent. Morphologically altered cells appeared enlarged, hyper-refractile, and intensely stained by hematoxylin. They neither assumed a crisscross pattern nor piled up to form a visible focus. Time-lapse cinegraph showed that the morphologically altered cells did not divide and were motile. The fluid from two human fibroblast cultures, inoculated 4 and 14 weeks previously with the ST sarcoma filtrate, induced fibrosarcoma in newborn kittens. The cell-free transmission of the ST feline sarcoma between kittens and from kittens to newborn dogs and marmosets was recently demonstrated (2, 14). The propagation in human cell cultures of a filterable agent from this feline sarcoma is now described. MATERIALS AND METHODS Feline sarcoma filtrate. The Snyder-Theilen line of sarcoma (14) was used. A crude 33% tumor suspension in tris(hydroxymethyl)aminomethane(Tris)-acetate buffer, pH 7.0, was homogenized in a mortar with sterile sand. Seven volumes of phosphate-buffered saline were mixed with three volumes of the tumor homogenate. The mixture was centrifuged at 1,500 rev/min for 15 min, and the supernatant fluid was passed through an ultrafine glass filter. The filtrate was stored in l-ml samples at below-60 C. The integrity of the glass filter was checked with a 10-ml suspension of Staphylococcus aureus; no bacterium was found in the filtrate. Nutrient medium. Nutrient medium consisted of 20% fetal calf serum in Eagle basal medium supplemented with nonessential amino acids. Penicillin and streptomycin were added to 50 units and 50,g/ml. Cell cultures. Human fibroblast cultures were originated from embryonic or sarcomatous tissues. Many of the human cell lines were gifts from the Naval Biological Laboratory, Oakland. A few were origi
The relative capacity of several types of human cells and tissue to produce interferon was studied. Types of cells and tissue included were fibroblasts from embryos, foreskins, and biopsied skins; amnion cells; peripheral leukocytes; established lymphoid cell lines; established heteroploid cell lines; and chorioamniotic membrane. When Newcastle disease virus was used as the inducer, fibroblasts and amnion cells produced more interferon per 106 cells than leukocytes, lymphoid cells, and heteroploid cells. Only minor variations in interferon-producing capacity were observed among fibroblasts from 36 persons. Culture passage level, cell concentration, and inducer were factors that significantly affected interferon production.
The relative capacity of several types of human cells and tissue to produce interferon was studied. Types of cells and tissue included were fibroblasts from embryos, foreskins, and biopsied skins; amnion cells; peripheral leukocytes; established lymphoid cell lines; established heteroploid cell lines; and chorioamniotic membrane. When Newcastle disease virus was used as the inducer, fibroblasts and amnion cells produced more interferon per 10 6 cells than leukocytes, lymphoid cells, and heteroploid cells. Only minor variations in interferon-producing capacity were observed among fibroblasts from 36 persons. Culture passage level, cell concentration, and inducer were factors that significantly affected interferon production.
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