The lateral mobility and surface distribution of Lyt-1, Lyt-2 and Lyt-3 on mouse thymocytes.

Fluorescein-conjugated monoclonal antibodies were used to investigate the properties of the Lyt-1, Lyt-2 and Lyt-3 antigens on the murine lymphocyte cell surface. Monoclonal antibody to Lyt-1 patched and capped on the thymocyte cell surface, whereas an Fab fragment of the antibody gave a uniform distribution of fluorescence on most cells and diffused freely in the plane of the membrane. Fluorescence photobleaching measurements showed that the intact antibody was relatively immobile on the cell surface, whereas the Fab fragment was freely mobile. Monoclonal antibody to Lyt-2 or Lyt-3 (which are linked to one another by disulfide bonds) gave a uniform distribution of fluorescence and was mobile on the cell surface. When cells were incubated with antibodies to Lyt-2 and Lyt-3 simultaneously, cells appeared patched and the lateral mobility of the antibodies was greatly reduced. Treatment of cells with either sodium azide or 2-mercaptoethanol followed by N-ethyl maleimide to reduce and block sulfhydryl groups inhibited the patch formation caused by simultaneous incubation with both Lyt-2 and Lyt-3 antibodies.