This IL-11 enzyme linked immunosorbent assay (ELISA) applies a technique called a quantitative sandwich immunoassay. The microtiter plate provided in this kit has been pre-coated with a monoclonal antibody specific to IL-11. Standards or samples are then added to the appropriate microtiter plate wells and incubated. After washing to remove unbound IL-11 and other components of the sample, biotin-conjugated polyclonal antibody specific to IL-11 is added and incubated. If present, IL-11 will bind and become immobilized by the antibody pre-coated on the wells and then become ``sandwiched'' by the biotin conjugate. In order to quantitatively determine the amount of IL-11 present in the sample, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. Avidin is a tetramer containing four identical subunits, each having a high affinity-binding site for biotin. The wells are thoroughly washed to remove all unbound HRP-conjugated Avidin and a TMB (3,3'5,5'