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Abstract
The MLr antigen, a mammary tumour virus-induced antigen on the surface of GR thymic lymphoma cells (GRSL) can be modulated from the cell surface upon incubation with specific antiserum for 1-2 h at 37 degrees C, followed by washing the cells. In contrast, a number of other cell-surface antigens on these GRSL cells cannot be modulated under similar conditions. These antigens include histocompatibility antigens of the H-2 complex (H-2.8 of the K-end and H-2dx(D) of the H-2dx haplotype) and two thymic markers, TL1.2 and Thy1.2. Antigenic modulation of MLr as tested by trypan-blue exclusion and by chromium51 release does not lead to a measurable change in the expression of H-2K, H-2D, TL and Thy1.2 antigens. These results could be confirmed by absorption analysis. The latter analysis showed that the number of antigenic sites per cell are about the same for MLr and the two H-2 antigens, while TL antigens are scarcer and Thy1.2 antigens are more abundant. The procedure of antigenic modulation showed that the MLr antigen resides on MTVgp52, the major protein of the envelope. There was no evidence of internal proteins, such as MTVp27, on the surface of GRSL cells.
Highlights
Summary.-The MLr antigen, a mammary tumour virus-induced antigen on the surface of GR thymic lymphoma cells (GRSL) can be modulated from the cell surface upon incubation with specific antiserum for 1-2 h at 37°C, followed by washing the cells
The procedure of antigenic modulation showed that the MLr antigen resides on MTVgp52, the major protein of the envelope
It has since been reported for a number of apparently unrelated cellsurface antigens, such as Epstein-Barr virus-associated membrane antigens (Smith et al, 1968), murine leukaemia virus-related antigens (Aoki & Johnson, 1972; Joachim et al, 1977), an antigen on human breast-cancer cells (Nordquist et al, 1977), HL-A antigens on human leucocytes (Sadeghee et al, 1975), measles virus-induced cell-surface antigen (Joseph & Oldstone, 1975) and, for ML and MLr antigens related to murine mammary tumour virus by our group (Calafat et al, 1-976; Feltkamp et al, 1978) and by Strzadala et al (1977)
Summary
Cells.-Thymic lymphoma cells. called GRSL cells (Hilgers et al, 1975a), were used as well as normal lymphoid cells of the GR strain. The antiserum was absorbed in vivo by injecting 1 ml i.p. in an MTV- young male mouse, usually of the BALB/c strain, and recovered by bleeding the mouse the day. It is a mixture of specific rabbit antibodies to MTV and mouse immunoglobulins. Normal rabbit serum was treated in the same way for control experiments. Such "rigorous" in vivo absorptions are needed to obtain specificity, and are superior to the usual in vitro absorption procedures as shown previously (Hilgers et al, 1972)
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