Suppressor cells in immunodepressed bladder and prostate cancer patients

Peripheral blood lymphocytes from 23 patients with bladder and prostate cancer were tested for their ability to respond in vitro to phytohemagglutinin, concanavalin A and allogeneic cells. The lymphocyte response was depressed in 15 patients (65 per cent), 13 with advanced disease, compared to peripheral blood lymphocytes from age-matched hospitalized control subjects tested on the same day. Furthermore, the hyporesponsive lymphocytes from 11 of the 15 cancer patients (73 per cent) inhibited the phytohemagglutinin, concanavalin A and mixed lymphocyte culture reactivity of normal lymphocytes in co-cultures (16 to 78 per cent suppression). In contrast, lymphocytes from control donors caused no suppression. Incubation of the patients' unseparated peripheral blood lymphocytes on plastic to remove adherent cells restored lymphocyte responsiveness and eliminated their suppressor activity. Returning the adherent cells to cultures with patients' autologous separated and normal lymphocytes recaptured the suppressive effect. Pre-incubation of the patients' lymphocytes with concanavalin A markedly enhanced their ability to suppress and induced moderate suppressor activity by normal lymphocytes. These data suggested that 1 mechanism for the depression of cell-mediated immunity seen in patients with advanced urological cancer may be owing to non-specific suppressor cells, possibly monocytes.