Targets of the stimulatory activity of IL2

Most cells of the immune system can express the high-affinity (IL-2Ra, (3, y) or the intermediate-affinity (lL-2R|3y) IL-2 receptors, either spontaneously or after stimulation. Consequently IL-2 has many targets (Figure 2).

T lymphocytes

The primary role of IL-2 is to expand activated CD4 and CD8 lymphocytes. On TU1 cells IL-2 acts in an autocrine fashion. IL-2 also induces the growth of Th2 and CD8 lymphocytes as a paracrine factor. IL-2 has no influence on the Th1/Th2 balance. On CD8 lymphocytes IL-2 stimulates cytotoxic activity. After stimulation T lymphocytes produce many cytokines and express the corresponding receptors. However IL-2 remains the main cytokine controlling the proliferative response of CD4 lymphocytes. The proliferation of purified CD4 lymphocytes stimulated by anti-CD3 is completely neutralized by anti-IL-2 monoclonal antibodies.

B lymphocytes

Activated B lymphocytes express the high-affinity IL-2 receptor and respond to IL-2. Under these conditions they proliferate intensively and produce immunoglobulins of the IgM, IgG and IgA isotypes. Different stimulations can induce the susceptibility of B lymphocytes to IL-2. Experimentally anti-Ig, or lipopolysaccharides (LPS) are good stimulators. Physiologically, in the context of T/B collaboration Th1 lymphocytes (or THl-like in humans) may induce an intense proliferation and differentiation of the B lymphocyte population. Unlike IL-4, IL-5 and transforming growth factor (3 (TGF(3), IL-2 does not exert an influence on isotype selection.

Natural killer (NK) cells

All NK cells are spontaneously sensitive to IL-2. In the majority of these cells IL-2 can stimulate cytotoxic activity without stimulating NK cell proliferation. In rare NK cells, expressing the high-affinity IL-2R, IL-2 stimulates both cytotoxic and proliferative responses. NK cells play a dominant role as the first defense barrier against viral infections and tumor growth.


IL-2 spontaneously stimulates the killing of tumor cells and bacteria by monocytes. Interferon y (IFNy) and LPS stimulate the appearance of high-affinity IL-2R on the surface of monocytes and therefore increase sensitivity to IL-2. During IL-2 stimulation monocytes produce a large array of mediators such as H202, prostaglandin E2 (PGE2), thromboxane B>, and tumor necrosis factor a (TNFa). These products may be responsible for the side-effects observed during IL-2 therapy.


Neutrophils are also sensitive to IL-2. Their antifungal activity is greatly enhanced by IL-2, perhaps because of the production of lactoferrin and TNFa by these cells.

IL-2 is a pleiotropic cytokine with proinflammatory activity both on the nonspecific arm of the immune system (NK cells, monocytes) and on the specific response generated by T and B cells.

How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book

Post a comment