CD8⁺ T cells can be primed in vitro to produce IL-4

IL-4 production by T lymphocytes from naive mice in response to stimulation by plate-bound anti-CD3 is concentrated among CD4⁺ T cells. In vitro stimulation of lymph node T cells with anti-CD3 plus IL-2 and IL-4 strikingly increases the frequency of cells that produce IL-4 in response to subsequent stimulation with anti-CD3 plus IL-2. Separation of these primed cell populations into CD4⁺ and CD8⁺ T cell by cell sorting reveals that the frequency of IL-4-producing cells in both population is similar. Verification that CD8⁺ T cells produce IL-4 is provided by the capacity of anti-IL-4 mAb to inhibit the response of the indicator cell line to the growth factor produced by the primed cells and by detection of IL-4 by an IL-4-specific ELISA. The in vitro "priming" of CD8⁺ T cells to produce IL-4 is not dependent on the presence of CD4⁺ T cells because highly purified CD8⁺ T cells can be stimulated to develop into cells capable of producing IL-4 by culture with plate-bound anti-CD3 plus IL-2 and IL-4.