title: Characterization of anti-CD8-resistant cytolytic T lymphocytes induced by multivalent cross-linking of CD8 on precursor cells.
abstract: The lytic activity of most CD8+ MHC class I allospecific CTL generated in vitro can be inhibited by anti-CD8 antibodies. Such inhibition has led to hypotheses that CD8/class I interactions normally contribute to the triggering of CTL with low or moderate avidity Ag-specific TCR by providing those CTL with auxiliary binding avidity. However, CD8 has also been proposed to play an active signaling role in T cell activation. We have recently reported that multivalent cross-linking of CD8 on CTL precursors in MLC does appear to mediate activation signals, and induces the generation of CD8+ MHC class I allospecific CTL whose lytic activity cannot be blocked by anti-CD8 antibodies. In our present study, we have further characterized such anti-CD8 uninhibitable effector cells. These CTL are resistant to blocking of their lytic function by anti-Lyt-3 mAb as well as anti-Lyt-2 mAb, but remain sensitive to blocking by anti-LFA-1 mAb, indicating that they do use non-CD8 cell adhesion molecules during target cell recognition and lysis. As a consequence of mAb-induced multivalent CD8 cross-linking during their generation, anti-CD8 uninhibitable CTL significantly reduce their cell surface expression of CD8, which permits their identification and facilitates their purification from heterogeneous MLC populations. Such anti-CD8 uninhibitable effector cells can be maintained as stable CTL lines, in the absence of anti-CD8 mAb after the initial induction period. The in vitro generation of anti-CD8 uninhibitable CTL, which may be highly enriched for cells bearing high affinity TCR, could represent a new experimental approach to studies of TCR gene usage and repertoire, as well as a potentially important strategy for the deliberate generation of high affinity effector cells for adoptive immunotherapy.
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, Bethesda, MD 20892.
authors.forename: S A
authors.initials: SA
authors.lastname: McCarthy
authors.forename: E
authors.initials: E
authors.lastname: Kaldjian
authors.forename: A
authors.initials: A
authors.lastname: Singer
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology*; D000918:Antibody Specificity; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D001667:Binding, Competitive; D016827:CD8 Antigens; D002460:Cell Line; D003432:Cross-Linking Reagents; D003602:Cytotoxicity, Immunologic; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010641:Phenotype; D013234:Stem Cells / Q000276:immunology* / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000145:classification / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D016827:CD8 Antigens; D003432:Cross-Linking Reagents