Cell growth, cytokine bioassays

Historically the functions of cytokines have been elucidated first with bioassays preceding immunoassays for cytokine quantification. The bioassay of a given cytokine is based on its bioactivity in a defined biological model, normally based on a certain cell line. Various approaches have been reported (1) proliferation tests— induction of cell growth (e.g., B9 cell line for IL-6) (2) tests for cytotoxicity— TNFa on WEHI164... 

Cytokines, which are protein mediators produced by immune cells, are involved in the regulation of cell activation, growth and differentiation, inflammation, and immunity. Measurement of cytokine production, as determined by techniques such as bioassay, radioimmunoassay, and enzyme-linked immunosorbent assay, has been used to examine various immune functions. 

Despite the diverse existing varieties of bioassays for cytokines, all are based on the protein s capacity to induce a measurable activity in cells and tissues. The cell responds in various ways including enhanced growth, growth inhibition, expression of cellular markers, cytotoxicity, or antiviral activity (Wadhwa et al., 1995). 

The ability to obtain cell clones that respond to cytokines and serve as source material for bioassays has aided the development of bioassays. The cell lines, obtained mainly from human or murine cancers, often depend on a cytokine for their growth and tend to be immortal, thus providing a unique homogeneous cell source, which may be distributed among laboratories (Mire-Sluis and Thorpe, 1998). The advent of recombinant DNA technology has enabled the cloning of specific cytokine receptors and their expression in any cell line (Canosi et al., 1996). In this way, a cell line can be created that responds specifically to almost any cytokine, and avoids the necessity to isolate a cell line with an endogenous receptor. 

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