Investigation on the inhibitory effect of tumor-derived immunosuppressive factor(s) on T lymphocyte proliferation.

Using five tumor cell lines, the effect of tumor-derived immunosuppressive factor(s) (TDSF) on T lymphocyte proliferation and its mechanism have been investigated. It was found that TDSF markedly inhibited PHA-stimulated T lymphocyte proliferation via a noncytotoxic mechanism. The inhibition increased in dose-dependent manner and the maximum inhibition was achieved when the factor was added at the initiation of the culture. When PBMC were preincubated with supernatants of tumor cells for 24 h, washed extensively and then cocultured with freshly prepared PBMC, similar suppressive effects were observed. The above results indicated that the activation of any suppressor cell subgroup may be one of the mechanisms of immunosuppressive action of TDSF.