[Interleukin 2].

Interleukin 2 (IL2) was discovered by Morgan et al. in 1976. Since then its unique functional property which induces the in vitro growth of antigen-stimulated T cells, especially cytotoxic T cells (CTL) opened a way to establish the T cell clone and gave us a way to explore the nature of T cell receptor molecule. Several kinds of T lymphoma cell lines or T hybridomas of mouse or human origin which produce IL2 have been established and the biochemical and functional properties of IL2 have been extensively studied. One of the important findings in Immunology is the discovery that IL2 exerts its function through the receptor on the antigen-activated T cells as peptide hormone does. The antigen-specific response of immunocompetent cells is assured by the antigen-specific appearance of IL2 receptor and by the fact that only the cells which have acquired the receptor can respond to IL2 to proliferate and differentiate to effector cells. Thus antigen-non-specific T cell factor such as IL2 can successfully function in the antigen-specific manner. Human IL2 cDNA has been cloned by the monumental achievement of Taniguchi et al. They determined the complete nucleotide sequence of IL2 cDNA and succeeded in the expression of IL2 cDNA in monkeys cell line, COS-7 cells. Their work gave us a chance to use pure IL2 which was produced by a cloned cDNA and thus a lot of reported studies on the functional properties of IL2 which have been done by using IL2 preparation contaminating a lot of other factors will be reevaluated and the true functions of IL2 will be established in near future. Up to present day, the in vivo effects of IL2 have not yet been established. Some encouraging studies showed the in vivo effects of IL2 and the successful therapeutic effects against tumor by co-administration of IL2 with tumor-specific CTL. It is now possible to use the product of a cloned IL2 cDNA to investigate the in vivo effects of IL2. It is highly expected that the promising results will be obtained and the application of several kinds of lymphokines such as IL2 to clinical fields will become possible.