The use of Fab' fragments in a screening method for the detection of human anti-tumor monoclonal antibodies.

The use of immunoperoxidase staining methods to detect human monoclonal antibodies that react with frozen tissue sections of human tumors is limited due to endogenous immunoglobulin present in the sections. The endogenous immunoglobulin produces a significant background staining which makes the detection of a specific reaction difficult and unreliable. A method of incubating the sections with papain fragments (Fab') of goat anti-human immunoglobulin was evaluated. It was demonstrated that Fab' fragments of goat anti-human polyvalent immunoglobulin can block endogenous immunoglobulin background staining after prolonged washing of tissue sections (20h) and thus facilitating the screening of monoclonal antibodies against frozen sections of tumor tissue.