Western bots are a type of immunoassay in which antibodies are used to detect and identify proteins. First sample proteins are separated by electrophoresis on a SDS-PAGE gel. Then, the proteins are transferred onto a nitrocellulose or nylon membrane. The membrane is then washed with a solution containing the protein-specific antibody. Secondary antibodies, are used to detect the presence of the primary antibody on the membrane surface. The secondary antibody is linked to a reporter enzyme that can be used for chemiluminescence or fluorescence detection. Assay specificity is a function of the primary detection antibody. Assay sensitivity is a function of the type of signal used and the detection platform.