Abstract
The antigen specific cell mediated cytotoxicity of MSV immune spleen lymphocytes to 51Cr labelled murine lymphoma cells was wholly abolished by pretreatment of the spleen cells with anti-theta antibody and complement. Early during the immune response to MSV the cytotoxic acitivity was inhibited by incubation of immune lymphocytes with "late progressor" or "early regressor" serum. Immune lymphocytes at later times were more refractory to such inhibition by serum blocking factors. Although unfractionated cytotoxic lymphocytes, irrespective of the time after MSV infection at which they were tested, were inhibited by soluble tumour associated antigen (TAA), a subpopulation of cytotoxic T cells was identified which was inhibited neither by antigen nor serum.
Highlights
Unfractionated cytotoxic lymphocytes, irrespective of the time after MSV infection at which they were tested, were inhibited by soluble tumour associated antigen (TAA), a subpopulation of cytotoxic T cells was identified which was inhibited neither by antigen nor serum
After incubation in 20-day MSV serum the cytotoxic potential of the cells was decreased to similar levels to the initial values obtained directly after removing the spleen cells from the intact animals. These data very strongly argue that the in vivo blocking effect is mediated by serum factors. Since such blocking was produced in the absence of target cells, the data suggest that the blocking factors are either free antigen or antigenantibody complexes, each of which would be capable of binding to cytotoxic lymphocyte receptors
The main emphasis of this work has been to analyse the ability of MSV tumour associated antigens (TAA) to block the direct cell mediated cytotoxicity significance of this phenomenon
Summary
Lymphocytes reacciated antigens in MSV regressor mice tive to the two avian TASA (Kurth and (Gorczynski, 1974a; Knight and Gorezyn- Bauer, 1972) have been detected by ski, 1975), and these immune T cells microcytotoxicity tests. Evidence was presented that such block- We have developed a 51Cr cytotoxicity ing factors in tumour bearer animals assay for lymphoid cells from MSV were antigen-antibody complexes (Sjo- inoculated mice with a view to answering gren et al, 1971). (1973) were unable to reproduce kinetics of the development of cell medithese findings It has recently ated cytotoxicity, the cell(s) responsible become apparent that progressor animals for this lysis and the relationship between contain a cell population able to block these cell types and those described using the in vitro activity of T lymphocytes alternative assays for immunity in this in a nonspecific manner
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