The cytokine array is an immunoassay similar to ELISA but capable of simultaneously measuring the levels of many proteins. Many biological processes such as apoptosis, inflammation, angiogenesis, immune response and migration often accompany changes of cytokine expression levels. Because of the extensive cross-talk between cytokines, a complete analysis of biological responses and functions must be obtained through multiplex assays. Cytokine arrays allow a much broader view of protein activity than can be obtained with multiple single-target ELISAs, immunoprecipitations, or western blots, which can be expensive, time consuming and can require specialized equipment. Thus, cytokine arrays are a rapid, sensitive, and cost-effective alternative method to detect multiple proteins in a single liquid sample like serum, plasma, cell culture supernatant, lysates, or other biological fluids.
Regulation of cellular processes by cytokines is a complex, dynamic process, often involving multiple proteins. Cytokine array screening improves the chances for discovering key factors, disease mechanisms or biomarkers related to cytokine signaling. The RayBio® C-Series Human Cytokine Antibody Array C5 detects 80 cytokines and was used to identify GM-CSF as a cytokine secreted by mesenchymal-like breast cancer cells that activate macrophages and promote metastasis1.
Membrane-based cytokine arrays use a panel of capture antibodies printed on a nitrocellulose membrane. The protein from the incubated sample is captured, and a detection antibody is also bound, creating an antibody-antigen-antibody sandwich. Chemiluminescent signals are then visualized on x-ray film or a digital image, allowing calculation of the relative amount of protein present. C-Series arrays use this method to measure relative protein expression levels across samples or experimental conditions. They are handled in a very similar manner to western blots.
Glass slide-based cytokine arrays also utilize the sandwich immunoassay principle, but require much less sample than the membrane-based arrays. The capture antibodies are spotted on 75mm x 25mm glass slide solid supports and a corresponding biotinylated detection antibody is utilized for resolving fluorescent signals. Each slide is spotted with either 8 or 16 identical antibody arrays (also called “subarrays”).
Quantibody® arrays are glass slide, quantitative cytokine arrays that combines the high specificity and sensitivity of ELISA with the high throughput of the glass chip-based array. Within each subarray, the capture antibodies along with controls are spotted in quadruplicate. Cytokine standards are provided with these arrays for calculation of target protein concentrations.
G-series arrays are semi-quantitative, glass-based arrays that measure relative protein expression levels across samples or experimental conditions. Unlike Quantibody®, G-Series arrays do not come with cytokine standards.
Label-based arrays differ from sandwich ELISA-based arrays primarily in the means of detection. Instead of using a second biotinylated antigen-specific antibody, sample proteins themselves are labeled with biotin prior to incubation with the capture antibodies. In this format, unintended antibody interactions are impossible, thus eliminating limitations on the size of the array panel. Available on both glass slide and membrane formats, L-Series arrays ideally suited for biomarker discovery studies and exploratory screens.