A collection of biochemical, cellular, and molecular techniques for unraveling and quantifying the events occurring between the initial contact of a cytokine at the membrane receptor and the eventual activation of gene transcription. The techniques used include the generation of transfectants, the immunohistochemical detection of cytokines in tissue sections, and optimized staining for cytoplasmic detection. Highlights include RT-PCR of small amounts of mRNA, in situ hybridization, biosensor analysis, measurement of biological activities and standardization, immunohistochemical and single-cell detection, and receptor isolation, characterization, and crystallization.