Augmentation of human lymphokine-activated killer cell activity in splenic lymphocytes by the combination of low-dose interleukin 2 plus interleukin 3.

The effect of interleukin 3 (IL-3) on lymphokine-activated killer cell (LAK) generation in splenic lymphocytes was examined in patients with gastric cancer or idiopathic thrombocytopenic purpura (ITP). IL-3 alone did not induce any significant LAK activity from splenic lymphocytes. However, IL-3 addition to the culture with low-dose IL-2 significantly augmented the activity of LAK cells. Spleen cells precultured with IL-3 for 2 days and then added to IL-2 became more potent LAK cells than the spleen cells cultured with the same doses of IL-3 plus IL-2. Phenotypic analysis using flow cytometry demonstrated that IL-2 alone increased in cells expressing CD2+, -11+, and -16+ cells, whereas IL-3 plus IL-2 induced the expansion of CD3+ and CD8+ cells in addition to CD2+, -11+, and -16+ cells. These results suggest that IL-3 plus IL-2 phenotypically induces not only natural killer-like LAK cells (CD2+, -11+, and -16+) but T cell-like LAK cells (CD3+ and -8+). We are now investigating the characteristics of immature T cell populations in the spleen responsive to IL-3 using T-cell receptor antibody.