However, after prolonged co-culture conditions (48 hours), anti-CD3+, anti-CD28+, and anti-CD49d+ stimulation of the T cells no longer led to increased cytokine production, suggesting either that the immunosuppressive role of the tumor cells, or cytokine production had already reached its maximum, with only tumor cells as a stimulus to the T cells (Fig. 2D). The gene discussed is CD28; the disease is neoplasm.