Interleukin-15 (IL-15) induces killer T-cell and LAK cell proliferation (growth of the “good guys” that seek out and destroy problematic cells) as it also promotes cell survival of human T and B lymphocytes, natural killer cells, and neutrophils (preservation of the other “good guys”).
Interleukin-15 (IL-15) is a potent immunoregulatory cytokine (definition below) produced by a variety of cell types including monocytes and epithelial cells. This T cell growth factor can enhance the cytolytic (cell dissolving) activity of antigen-specific T cells and lymphokine-activated killer cells.
Natty (I'm sure you will be seeing this word a lot, so a good explanation will help you establish a baseline comprehension for what the hell is going on)
Cytokines:
Cytokines such as interleukins (IL), colony stimulating factors (CSF), tumor necrosis factors (TNF), and interferons (IFN) constitute a complex network of small, secreted protein mediators which act on cells at hormonal concentrations through high-affinity receptors. They represent the elements (the vocabulary) of a communication system between cells involved in the inflammatory reaction and many target tissues such as the vessel wall, the liver, the bone marrow, and the central nervous system (3). Communication may occur at very short distance between two cells that are attached to each other, at moderate distance within a small tissue area or even at long distance, acting systemically throughout the entire organism. The longdistance effects mainly occur under extreme situations, the majority of immune responses being rather local than systemic (2). The physiological importance of cytokines is comparable to that of other signalling systems such as neurotransmitters and endocrine hormones.
Since the discovery of IL-2 in 1976 (1, 4), a whole range of immunologically active cytokines have been discovered, which are essential for many proliferative and differential functions of immune cells. The majority of cytokines have a variety of effects on many different cells. There is also considerable functional overlap, nevertheless individual cytokines act distinctively, sometimes synergistic, sometimes antagonistic to each other. Further regulation is provided by the synthesis of subsets of cytokines by different cells. Characteristic sets of cytokines are produced by macrophages, B cells, T cells, granulocytes and several other cell types. Thus, cytokines interact in complexity and represent a very sophisticated and versatile communication network that is essential for the immune system to master the various defence strategies.