The Human CD21 ELISA Pair Set is for the quantitative determination of Human CD21.This ELISA Pair Set contains the basic components required for the development of sandwich ELISAs.The Sino Biological ELISA Pair Set is a solid phase sandwich ELISA (Enzyme-Linked Immunosorbent Assay). It utilizes a monoclonal antibody specific for CD21 coated on a 96-well plate. Standards and samples are added to the wells, and any CD21 present binds to the immobilized antibody. The wells are washed and a horseradish peroxidase conjugated rabbit anti-CD21 monoclonal antibody is then added, producing an antibody-antigen-antibody ``sandwich''. The wells are again washed and TMB substrate solution is loaded, which produces color in proportion to the amount of CD21 present in the sample. To end the enzyme reaction, the stop solution is added and absorbances of the microwell are read at 450 nm.