Novel cell junctions induced by activating Thy-1-specific antibodies.

KT16, like other anti-Thy-1 antibodies, induces T cell aggregation. Protein A-gold labelling shows the antibody to be concentrated along areas of intercellular contacts. Electron micrographs of KT16 treated T cells reveal a consistent type of junction between the cells. We demonstrate that this type of cell junction is Thy-1 specific, is predominantly the property of antibodies directed against a particular epitope, and is distinct from cellular aggregation caused by concanavalin A or anti-CD3 antibodies. The degree of adhesiveness induced by different anti-Thy-1 antibodies is related to their mitogenic capacity.