The "erythrocyte receptor" of T-lymphocytes and T11 target structure (T11TS): complementary cell interaction molecules involved in T-cell activation.

The CD2 or T11 glycoprotein on T-lymphocytes is the receptor for both sheep and human erythrocytes in the formation of spontaneous ("E"-)rosettes. Recent evidence employing monoclonal anti-T11 antibodies suggested that T11 is also a signal transducing molecule with a function in T-cell activation. The present report summarizes the identification of T11 target structure (T11TS), a natural ligand of T11, and its biochemical and functional characterization. T11TS is defined by a mAb to sheep erythrocytes that completely blocks their binding to CD2. It is a glycoprotein of 42 kDa MW expressed on all types of blood cells and some other tissues. While the anti-T11TS mAb used is specific for sheep cells, an antiserum raised to purified T11TS also blocks human autologous E-rosetting. Evidence is presented that the human lymphocyte function associated antigen (LFA)-3, which had recently been shown to be the likely human ligand of CD2, is the structural and functional human homologue of T11TS. Functional studies on T-cell activation employing sheep erythrocytes as one ligand of CD2 indicate that binding of T11TS to the E-receptor provides one of the signals required for T-cell activation through the CD2 molecule.