Interleukins, Lymphokines and Related Peptides

Introduction

Interleukins, one kind of lymphokines which is a hormone-like polypeptide substance produced by activated lymphocytes that does not have the structure of an antibody and cannot bind to an antigen. Different lymphokines can express a variety of biological activities, which can act on the corresponding target cells to cause changes in the characteristics or functions of the target cells. Lymphocytes act on adjacent or distant target cells by means of lymphokines, which is parallel with the action of antibodies and is an important way to achieve immune and immune regulation functions. At least 38 kinds of interleukins have been discovered, named IL1~L38, which are complex in function, networked, and complexly overlapped. Interleukin (IL)-2, 3, 4 and 5 are all produced by lymphocytes and belong to the “real” lymphokines while IL-1 and 6 are mainly produced by mononuclear macrophages, and can also be produced by some lymphocyte culture strains, which are both mononuclear cytokines and lymphokines.

Mechanism

Essentially, it is accomplished through the exchange of information between cells, in which lymphokines act as a medium, which seems to be very similar to hormones. The IL-1 and 2 are essential for T-cell proliferation to antigen. T lymphocytes in response to antigen is dependent upon monocytes/macrophages which process and present the antigen and are a source of IL- 1. It is generally held that this stimulates T cells to produce IL-2 and receptors for IL-2; the interaction of IL-2 with its receptor stimulates T-cell proliferation. IL-2 is made by T cells; to date no other cell has been shown to produce this lymphokine. The action of IL-2 is predominantly on T cells or closely related lymphocytes (natural killer, NK, or lymphokine-activated killer cells, LAK), although it also exerts effects on B cells and macrophages. In contrast, IL-l is extremely pleiotropic acting, not only on other lymphoid cells but also on a variety of non-lymphoid targets. What’s more, T lymphocytes produce a number offactors affecting the growth and differentiation of B lymphocytes. Both IL-4 and IL-5 have growth and differentiation activities for B cells and IL-6 differentiation activity. In addition, IL-l and IL-3, as well as IL-2, are reported as promoting B-cell growth and differentiation.

Application

Interleukins play an important role in transmitting information, activating and regulating immune cells, mediating T and B cell activation, proliferation and differentiation, and in inflammatory responses. The IL-2 can induce and enhance cytotoxic activity, and the current research on the treatment of certain diseases with IL-2, especially for cancer treatment, has been widely carried out. In addition, it also can applied to the treatment of viral infections by enhances the activity of CTL and NK cells, induces the production of interferon, and enhances the body's anti-infective immunity. Therefore, people with AIDS and other congenital or acquired cellular immune function have the effect of preventing and treating various viral infections. The IL-3 can be used to treat children with myelodysplastic syndrome, leukemia.

References

1. Hamblin A. S. (1991). Lymphokines and interleukins. Immunology Supplement, (Suppl1), 39-41.
2. Strober W., & James S. P. (1988). The Interleukins. Pediatr Res, 24 (5), 549-557.