Cytokines and chemoattractive
cytokines (
chemokines) are present in a wide variety of body fluids such as plasma, cerebrospinal fluid, bronchoaveolar fluid, amniotic fluid, synovial fluid,
middle ear effusion fluid, and urine.
Cytokines can be detected using classical solid-phase sandwich immunoassays such as
enzyme-linked
immunosorbent assay (ELISA) or with a bead based multiplex immunoassay (MIA). The physical chemical properties of the different body fluids (such as pH and total
protein content) differ, which may have an impact on the outcome of the
cytokine assay. Both ELISA as well as MIA
cytokine detection systems are constructed by sandwiching the
protein of interest between a capture and reporter antibody. When the
biological sample contains heterophilic
antibodies (such as in patients with auto-
immune diseases), these non-specific
antibodies can cause false positive results. During pathological conditions,
cytokines may be found over a wide concentration range; likewise have to cover this dynamic range in a similar fashion. The correct (statistical) analysis of standard curves and (multiplexed) data are critical for proper interpretation. Classical ELISA based
cytokine assays are robust, easy to use and very well suited for measurement of single
cytokines. Due to an increased interest in the integral approach to understand biological processes (the omics era), multiplex immunoassays for detection of
cytokines and the interpretation of these assays are gaining popularity.