Structure and function of interleukin-4 and its receptor.

Abstract

Interleukin-4 (IL-4) is a highly pleiotropic cytokine which has been extensively studied in the last decade. It is predominantly produced by activated T lymphocytes, mast cells, and basophils [1–5]. Consistent with the pleiotropic nature of this molecule, the receptors for IL-4 have been identified on many different cell types, including hematopoietic and non-hematopoietic cells (see reveiws [6,7]). Recent studies have identified a couple of novel functions of IL-4 which were previously unidentified. We and others have shown that IL-4 receptors are expressed on solid human tumor malignancies and that IL-4 has growth inhibitory and immunomodulatory effects on many solid tumor cell types [8–13]. It is also reported that IL-4 may play a major role in the progression of acquired immune deficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV-1) [14–16]. It has been shown that the earlier stages of HIV-1 infection are dominated by IL-4 production with concomitant inhibition of IL-2 production [17]. However, the role of IL-4 in AIDS progression is questionable because recent studies did not observe increased IL-4 production in cells from lymph nodes or from periphery of AIDS patients [18,19]. Thus the role of IL-4 in the pathophysiology of AIDS is controversial.