Studies on mouse Moloney virus induced tumours: II. Detection of p30 in the serum of mice with Moloney leukaemia by in vitro blocking of complement dependent antibody mediated cytotoxicity

Abstract

Sera from Balb/c mice bearing Moloney leukaemia block complement dependent antibody mediated cytotoxicity of an antiserum prepared in rats against syngeneic Moloney virus induced lymphomata when either spleen cells from mice bearing Moloney leukaemia (M) or an in vitro line of Moloney virus transformed cells (MSC) are used as targets. This antiserum has been shown to recognize p30, the major internal virion protein, as a cytotoxic target on these cells. Viral particles were identified by electron microscopic examination of pelleted material obtained from leukaemic sera after high speed centrifugation. However, removal of virus did not affect the capacity of the leukaemic sera to absorb cytotoxicity of rat ILR-3 for MSC targets, and only depressed somewhat its ability to absorb activity of the same antisera against M targets. Virus-free leukaemic sera also blocks complement dependent antibody mediated cytotoxicity of an antiserum prepared in goats against the gs3 determinant of p30. This indicates that the material in leukaemic sera responsible for the in vitro block of antibody mediated cytotoxicity was p30. A lesser degree of block was observed with sera obtained from normal Balb/c mice, but the nature of material responsible is as yet undefined.

Studies on mouse Moloney virus induced tumours: I. The detection of p30 as a cytotoxic target on murine Moloney leukaemic spleen cells, and on an in vitro Moloney sarcoma line by antibody mediated cytotoxicity

“…The identification of p30 in leukaemic mouse sera and the relevance of circulating p30 to the tumour status of the animal are discussed in the following paper by Epstein and Knight (1975). The results obtained here confirm and extend those previously reported with MLV-G induced lymphomata in the rat (Knight, Mitchison and Shellam, 1975 (Massicot et al, 1971).…”

“…A manuscript to follow also offers confirmatory evidence, as in it we demonstrate that Moloney leukaemic serum contains p30 and also absorbs the cytotoxic activity of Rat ILR-3 against MSC and M target cells (Epstein and Knight, 1975).…”

Studies on a gross‐virus‐induced lymphoma in the rat. II. The role of cell‐membrane‐associated and serum p30 antigen in the antibody and cell‐mediated response

“…The abrogation of the inhibition of CMC by anti-p30 sera identifies p30 as an inhibitory component of tumour-bearer rat sera. In a similar study, p30 has been detected in leukacmic mouse sera (Epstein and Knight, 1975). In the rat, the serum inhibitory activity, measured by inhibition of antibody cytotoxicity, is excluded by Sephadex G200 (Mitchison, 1974), suggesting that the antigen is in the form of a large molecular weight complex, either as cell membrane or viral fragments, or bound to antibody.…”

“…Specimens were fixed in osmium tetroxide and glutaraldehyde and, after staining with uranyl acetate and Reynolds' lead citrate, were examined in an AEI EM6B electron microscope as described elsewhere (Epstein and Knight, 1975). The samples were processed by Mr. R. Mahoney.…”

The Specificity of Effector T Cells Activated by Tumours Induced by Murine Oncornaviruses

“…Analysis of these sera on anti-immunoglobulin columns suggests that both free antigen and antigen-antibody complexes may be responsible for the inhibitory effect , Gorczynski & Knight 1975b. The circulating antigens in progressor sera from mice with Moloney sarcomas have not been characterised, although serum from mice with Moloney leukaemias has been shown to contain p30 (Epstein & Knight 1975b).…”