A continued evaluation of the experimental conditions of a Con A-induced suppressor test system.

As shown previously, the suppressor activity measured by the Con A mixed lymphocyte culture assay exhibited a pronounced dependence on the technical parameters. In the present study it is shown that the length of the suppressor generation period, between 24 and 96 hours, had only a modest influence on the suppressor activity. However, when the activity in the responder system was high, there seemed to be a trend towards a slight increase of the suppressor level using a long generation period, i.e. 72 to 96 hours. An increase of the suppressor cell/responder cell ratio from 1/10 to 1/2 was followed by a rising suppressor level; a further increase of the ratio had no significant influence on the suppressor activity. A decrease of the ratio below 1/10 showed variable results: stimulation, no effect and suppressor activity. This variability might be due to technical reasons. DNA-synthesis was not necessary for the mechanisms involved in the Con A-elicited suppressor activity. No suppressor activity was obtained by Con A treatment of cells other than peripheral blood mononuclear cells, viz. autologous erythrocytes, allogeneic fibroblasts and allogeneic osteogenic sarcoma cells.