The ELISPOT assay is designed to enumerate cytokine producing cells in a single cell suspension. This method has the advantage of requiring a minimum of in-vitro manipulations allowing cytokine production analysis as close as possible to in-vivo conditions in a highly specific way. This technique is designed to determine the frequency of cytokine producing cells under a given stimulation, and the follow-up of such frequency during a treatment and/or a pathological state. Elispot assay constitutes an ideal tool in the TH1 / TH2 response, vaccine development, viral infection monitoring and treatment, cancerology, infectious diseases, autoimmune diseases and transplantation.
The Elispot assay is based on sandwich immuno-enzyme technology. Cell secreted cytokines or soluble molecules are captured by coated antibodies avoiding diffusion in supernatant, protease degradation or binding on soluble membrane receptors. After cell removal, the captured cytokines are revealed by tracer antibodies and appropriate conjugates.
After cell stimulation, locally produced cytokines are captured by IL-10 and IL-4 specific monoclonal antibodies. After cell lysis, trapped cytokine molecules are revealed by a secondary anti- IL-10 FITC conjugated antibody and a biotinylated anti-IL-4 antibody. Those are in turn recognised by anti-FITC green fluorescent dye and streptavidin-phycoerythrin conjugates. PVDF-bottomed-well plates are then read under a UV light beam. Green fluorescent spots indicate IL-10 production while IL-4 is revealed by red spots. Yellow spots will indicate dual cytokine producing cells.
Interleukins (ILs) are a large group of cytokines that are produced mainly by leukocytes, although some are produced by certain phagocytes and auxiliary cells. ILs have a variety of functions, but most function to direct other immune cells to divide and differentiate. Each IL acts on a specific, limited group of cells through a receptor specific for that IL. Human IL10 is a non glycosylated polypeptide consisting of 160 amino acids. There is 73% homology between the human and mouse IL10 proteins, however, the human IL10 acts on both human and mouse target cells, while the mouse IL10 has species specific activity. The cellular sources of IL10 are CD4+ T cells and T cell clones, thymocytes, B cells and B cell lymphomas, macrophages, mast cell lines and keratinocytes. IL10 will stimulate the growth of stem cells, mast cells and thymocytes. IL10 enhances cytotoxic T cell development, and costimulates B cell differentiation and immunoglobulin secretion. IL10 inhibits cytokine production by macrophages and suppresses macrophage class II MHC expression. The human IL10 gene is on human chromosome 1.
IL4 is a pleiotropic cytokine produced by activated T cells, mast cells and basophils. It is a ligand for Interleukin 4 receptor. The Interleukin 4 receptor also binds to IL13, which may contribute to many overlapping functions of this cytokine and IL13. IL4 elicits many different biological responses, but has two dominant functions. The first is regulating differentiation of naïve CD4+ T cell to the Th2 type. Th2 cells produce IL4, IL5, IL10 and IL13, which tend to favor a humoral immune response while suppressing a cell mediated immune response controlled by Th1 cells. STAT6, a signal transducer and activator of transcription, has been shown to play a central role in mediating the immune regulatory signal of this cytokine. The second is regulating IgE and IgG1 production by B cells. Two alternatively spliced transcript variants of this gene encoding distinct isoforms have been reported.