Antibody capture assays are often the easiest and most convenient of the hybridoma screening methods. In this procedure, proteins in solution or in a cell lysate are separated according to size by gel electrophoresis and then transferred by blotting to a nitrocellulose sheet. Antigen bound to the solid substrate is incubated with the primary antibody, and the resultant antibody–antigen complexes are detected by a horseradish peroxidase (HRP)–conjugated secondary antibody and a chemiluminescent substrate for HRP.