Identification of FTS (facteur thymique serique) on thymus ultrathin sections using monoclonal antibodies.

Using a new immunoelectromicroscopical technique, this study confirms the localization of the 'facteur thymique sérique' (FTS) in the reticulo-epithelial cells of mouse thymus. The use of anti-FTS monoclonal antibodies on ultrathin sections for electron microscopy reveals FTS in cytoplasmic vacuoles, labelling density depending on the density of the vacuolar content. The successful application of this technique opens the way to its use for double-immunolabelling.