FITC and HRP conj ugated secondary antibody used to detect nanogram – picogram levels of rabbit IgG by dot blot on nitrocellulose membrane. 4 ul each of serial 1 in 4 dilutions of rabbit IgG were dotted on nitrocellulose and allowed to dry. Membrane was blocked in 3% BSA for 10 minutes dried for later use and rewetted with blocking buffer.