Effects of stress on growth of transplanted hepatic tumours and immune responses

Growth of transplanted hepatic tumours (T-9) was enhanced in immune rats under stress, compared with immune rats in an unstressed condition. Compared with unstressed immune rats, killer activity of mononuclear cells infiltrating the tumours against T-9 cells was significantly reduced in stressed immune rats. In contrast, killer activity of splenocytes obtained from stressed immune rats against T-9 cells was elevated compared with that from unstressed immune rats. In addition, natural killer cell activity of mononuclear cells infiltrating the tumours obtained from stressed immune rats was significantly reduced compared with that from unstressed immune rats. Cell populations infiltrating tumour tissues were identified by flow cytometric analysis. The percentage of CD8+ cells in mononuclear cells isolated from tumour tissues of stressed immune rats was reduced compared with that of unstressed immune rats. Furthermore, interleukin-2 responsiveness of splenocytes was suppressed in stressed immune rats, whereas T cell function as reflected by phytohaemagglutinin- or Concanavalin A-reactivity was unaffected by stress. Collectively, it is likely that stress suppressed the generation of cytotoxic cells from the spleen cells of immune rats.