Effect of BCG on concanavalin A-induced suppressor cell activity and lymphocyte stimulation in stage I melanoma.

Suppressor cell activity was determined in 14 patients with stage I melanoma, treated with or without adjuvant Bacillus Calmette-Guerin (BCG) immunotherapy, and in 27 normal healthy volunteers. An in vitro test system was used in which peripheral blood mononuclear cells when stimulated with concanavalin A (ConA) significantly suppress proliferative responses of fresh autologous mononuclear cells. In addition, lymphocyte stimulation capacity to optimal and suboptimal concentrations of phytohemagglutinin (PHA) was determined in 44 BCG treated or not BCG treated melanoma patients and in 40 normal individuals. ConA induced suppressor cell activity was significantly (p less than 0.02) impaired in BCG treated melanoma patients (21.3 +/- 3.1% suppression) when compared to not BCG treated patients (39.8 +/- 5.6%) or to normals (38.3 +/- 9.3%). Lymphocyte stimulation capacity was depressed in all melanoma patients when suboptimal concentrations of PHA were used but was found to be not significantly altered at optimal concentration of PHA. The present study reveals that BCG immunotherapy impairs ConA induced suppressor cell activity in melanoma patients but does not influence lymphocyte stimulation capacity.