Analysis of cellular events involved in T cell stimulation by concanavalin A as a function of cell concentration.

To investigate cell-to-cell interactions in T cell stimulation by concanavalin A (Con A), three distinct events involved in the stimulation--production of interleukin 2 (IL 2), emergence of IL 2 receptors, and responses of cells bearing IL 2 receptors to IL 2--have been separately determined as functions of the cell concentration. Results obtained at concentrations as low as 5 X 10(4) cells/ml showed that both the emergence of IL 2 receptors and the induction of DNA synthesis by IL 2 of lymphocytes bearing IL 2 receptors occurred in a manner independent of the concentration of cells, whereas the production of IL 2 depended greatly on the cell density. These results suggest that the production of IL 2 requires cell-to-cell interactions, but the other two events do not.