title: Pleiotropic loss of activation pathways in a T-cell receptor alpha-chain deletion variant of a cytolytic T-cell clone.
abstract: Untransformed T-cell clones maintained in culture are dependent on signals transmitted through their antigen receptors (Ti; alpha and beta chains associated with the CD3 molecules) for growth and effector function. For cytolytic T cells (CTL), Ti stimulation also activates the killing machinery and induces synthesis of gamma interferon (IFN-gamma) messenger RNA and IFN-gamma secretion. The Thy-1 molecule, expressed on all murine cells of the T-cell lineage, has been suggested to function in transmembrane signalling, based on the ability of some anti-Thy-1 monoclonal antibodies (mAb) to activate T cells. Recently, it was suggested that Thy-1 could function as a signal-transduction molecule when expressed in B-cell lymphomas after transfection of the gene, leading to speculation that the molecule was part of an activation pathway independent of the Ti/CD3 structures. Here we report the immunoselection of a variant CTL clone which has lost expression of mRNA for the alpha-chain of the Ti. The Ti- variant was defective in lectin-mediated activation whether measured by increase in intracytoplasmic Ca2+, CTL effector function or IFN-gamma synthesis. The variant, which expressed normal levels of Thy-1, was also unresponsive to Thy-1 mAb activation as measured by IFN-gamma secretion, whereas it responded to calcium ionophore plus phorbol ester. These results indicate that in a non-transformed, functional mature T-cell, Thy-1 mediated signalling is not an alternative to, but might depend on elements associated with the Ti/CD3-mediated T-cell activation pathway.
mesh_terms: D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D014644:Genetic Variation; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D018800:Thy-1 Antigens
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D011948:Receptors, Antigen, T-Cell; D018800:Thy-1 Antigens; D002118:Calcium