Human interleukin-4: An immunomodulator with potential therapeutic applications

Human interleukin-4 (IL-4) is a 20kDa cytokine produced by activated T cells and has an extensive range of stimulatory and inhibitory effects on the wide range of cells which express its receptor. It specifically promotes the immunoglobulin class switch to IgE and IgG₄ and potently co-stimulates with CD40 monoclonal antibodies the long term proliferation of human B cells. It has variable effects on T cells, but predominantly has inhibitory actions on monocytes suggesting a potential therapeutic role as an anti-inflammatory agent. There is evidence for indirect anti-cancer activity of IL-4 both in animal models and in in vitro studies on human tumour infiltrating lymphocytes. In addition, IL-4 directly inhibits the in vitro proliferation of the majority of B cell neoplasms. Phase I studies of IL-4 in patients with cancer have commenced and promising observations have been made in patients with haematological malignancies receiving low, well-tolerated doses.