Medical Device Link . A multisystem approach to cytokine research

Researchers and clinicians are increasingly looking for soluble indicators that can provide clues to immune function or be used as markers of disease progression in immune disorders, transplantation medicine, and infectious diseases. Among the markers that have attracted the attention of researchers are the cytokines, small peptide proteins with hormone-like activity that are secreted by cells of the immune system in response to cell activation and the initiation of the immune response. Cytokines play a central role in communication among cells of the immune system. They are soluble mediators and regulators of innate and specific immunity. Additionally, cytokines promote the growth and differentiation of leukocytes and blood-cell precursors. They are central agents in the activation and proliferation of antigen-specific immune cells, activities that are among the earliest steps on the way toward developing an immune response. This article discusses the relationship of cytokines to immune function, the potential of cytokines as soluble indicators of immune function and disease progression, and the need for a comprehensive approach to study them. Additionally, the article examines the advantages of flow cytometry as a tool for a multisystem study of cytokine biology. Because of the interplay among cytokines and the cells that respond to their biological activity, understanding cytokine biology requires study of changes in the plasma levels of soluble cytokines, changes in cell-surface cytokine receptor expression, and the expression of intracellular cytokines by individual cell subpopulations. Changes in plasma levels of cytokines, or in the ability of cells to produce or respond to cytokines, can be used as in vitro indicators of immune dysfunction or disease progression. High levels of such inflammatory cytokines as Interleukin-1 (IL-1), Interleukin-6 (IL-6), and tumor necrosis factor (TNF- ) can be indicators of sepsis. Various clinical conditions (including HIV) have been shown to reduce both cytokine production and cytokine-receptor