The 107.3 clone has an unknown specificity. Trinitrophenal (TNP), the immunogen, is a hapten not expressed on human or mouse cells. In the absence of specific binding, this antibody may bind non-specifically to Fc receptors. The immunoglobulin from clone 107.3 was selected as an isotype control following screening for low background on a variety of mouse and human tissues. This antibody is routinely tested by ELISA analysis. Other applications were tested during antibody development only or reported in the literature.