Sequential expression of lymphokine genes during phytohemagglutinin-stimulated mitogenesis of normal human peripheral mononuclear cells.

Expression of lymphokine genes including interleukin 2 (IL-2), interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon gamma (IFN-g), tumor necrosis factor (TNF) and lymphotoxin (LT) were sequentially monitored in peripheral blood mononuclear cells by Northern blot analysis after stimulation with phytohemagglutinin (PHA). The pattern of the expression of lymphokine genes following PHA stimulation as categorized into two types. Type 1 was characterized by rapid appearance of mRNA and by early maximum accumulation. Type 2 was characterized by the prolonged expression and late peak time. Lymphokines including IL-2, IL-3 and GM-CSF belong to type 1 and IFN-g, TNF and LT belong to type 2. Since lymphokines in type 1 are known to act on hematopoiesis in a stimulatory manner, whereas type 2 show an inhibitory action, this sequential expression of lymphokines following mitogen stimulation may reflect some biological feedback mechanism.