In this article we summarize the data concerning the expression of immediate early gene (IEG), c-fos, in brain cells, which encodes for one of the interleukin-2 (IL-2) cytokine transcriptional factors. The main molecular features and tissue-specific differences of IL-2 and IL-2 receptors in the brain are also discussed. Various forms of stress stimulated the expression of c-fos and IL-2 genes in central nervous system (CNS) neurons has been shown after different stressor stimuli. Stress activated IEG expression in cells of definite hypothalamic structures.

Antigen injection led to the activation of c-fos and IL-2 gene expression specifically in the cells of definite hypothalamic nuclei and in other areas of rat brain. A temporospatial pattern of activation of hypothalamic structures was found consistently in response to exposure to antigen, which was different from that induced by other stressors.

Short synthetic immunomodulating peptides influenced IEG expression in immune and nervous system cells. Definite physical factors, like Extremely high-frequency electromagnetic millimeter waves (EHF) skin irradiation, modulated (mostly decreased) the stress-induced stimulation of IEG genes in hypothalamic neurons. We discuss the possible role of the JAK-STAT and Ras-MAPK signal transduction pathways in IL-2 gene expression in lymphocytes and in nerve cells.