Large particle fraction obtained by the technique of Sjögren and Motet (1969) can be treated at acid pH, to elute immunoglobulins from hamster tumors induced by injection of SV‐40 transformed fibroblasts (TSV5Cl2). The eluate contains IgG27S, as well as two fragments having molecular weights of about 67,000; one of these, Fc, migrates in the β region, and the other, F(ab), migrates in the slow y region. This eluate, tested on TSV5Cl2in culture, contains some cytotoxic antibodies and antibodies against T antigen and cytoplasmic antigen.
A clone of hamster fibroblasts tramformed by SV40 virus (TSVKCL,) induced antibodies in hamsters against new antigenic constituents not present in the untransformed fibroblasts. The antibodies in the immune sera against histocompatibility antigens and those against nuclear T antigen were absorbed. The absorbed sera contained antibodies which agglutinated the transformed cells. The sera contained also precipitatiitg antibodies against new antigens present in a crude extract of TSVKCL2. These antibodies were directed to common new antigens present in SV40-transformed fibroblasts from different species. ImmunoJluorescence and the '' indirect enzyme-labelled antibody technique '' were used for the cellular localization of the antigens corresponding to the precipitating antibodies. Both techniques showed that these antigens were localized in the cytoplasm, mostly in the microsome-ribosomal fractions, much less on the cell membrane and not at all in the nucleus.
NEW ANTIGENS IN SV40 TRANSFORMED CELLS
IN SEVERAL CELL LINES OF DIFFERENT SPECIES TRANSFORMED BY T H E SV40
I. DEMONSTRATTON OF THREE NEW ANTIGENIC CONSTITUENTS
The soluble components of different cell lines in various species (hamster, mouse, rat and dog) were compared by means of precipitation test in agar. Some lines were spontaneously transformed, others were transformed by S V40 virus and oncogenic viruses. The utilization of rabbit and hamster antisera, speciftc for a clone of SV40 transformed cells ( T S V , ClJ demonstrated the presence of three new antigens in the various cell strains transformed byS V40. These antigens are dinerent from the nuclear T antigen and probably alJo from the transplantation antigen located on the crll membrane.
The sera of hamsters carrying tumours induced by injection of TSV5Cl2 cells and the sera of animals immunized with these cells or with SV40 itself or its purified capsids have a slow cytotoxicity activity in the presence of fresh guinea pig complement on SV40‐transformed cell strains of any origin. The responsible antigen is dependent on the SV40 genome and is associated with the cytoplasmic membranes of the transformed cells. By means of absorption of the antisera with subcellular fractions it has been correlated with antigen “C” present in the cytoplasm of SV40‐transformed cells. It is different from antigen “S” shown by the immunofluorescence test, and its relation with TSTA is discussed.
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