title: Induction of dendritic cell costimulator molecule expression is suppressed by T cells in the absence of antigen-specific signalling: role of cluster formation, CD40 and HLA-class II for dendritic cell activation.
abstract: Full activation of T lymphocytes by dendritic cells (DC) during antigen presentation is known to require the interaction of several inducible receptor-ligand pairs. We have postulated that the reciprocal activation of DC by T lymphocytes is also important. Potential signalling molecules that might increase the stimulatory capacity of DC during antigen presentation to T lymphocytes were tested using an in vitro model. Fresh human blood DC were cocultured with CD4+ and CD8+ allogeneic or with autologous T lymphocytes plus Staphylococcus superantigen A (SEA). Surprisingly, costimulator expression on DC cocultured with T lymphocytes was reduced in comparison to DC cultured alone. However, the minority (10-30%) of DC clustering with T lymphocytes showed antigen-specific up-regulation of the CD40, CD80 and CD86 costimulator molecules, whereas the non-clustered DC (70-90%) had less up-regulation than control DC cultured alone and did not respond to antigen-specific triggering. Monoclonal antibodies (mAb) to CD40 ligand (CD40L) and human leucocyte antigen (HLA)-DR, but not lymphocyte function-associated antigen-1 (LFA-1), LFA-3 or HLA-class I, significantly inhibited the T-lymphocyte induction of DC costimulator expression. Since HLA-class II, but not HLA-class I mAb, inhibited allogeneic T-lymphocyte-mediated activation of DC, CD4 T lymphocytes appear to be the main subset activating DC in the mixed lymphocyte reaction. Cross-linking of CD40, but not HLA-class II, up-regulated DC or B-cell costimulator expression. Although direct class II signalling does not appear to play a role in DC activation, antigen-specific T-cell recognition contributes via other mechanisms to regulate DC activation.
authors.affiliation: Haematology/Immunology Research Group, Christchurch Hospital, New Zealand.
authors.forename: A D
authors.initials: AD
authors.lastname: McLellan
authors.forename: A
authors.initials: A
authors.lastname: Heiser
authors.forename: D N
authors.initials: DN
authors.lastname: Hart
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017951:Antigen Presentation; D018122:B7-1 Antigen / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D023201:CD40 Ligand; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology*; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D008562:Membrane Glycoproteins / Q000276:immunology; D013211:Staphylococcus aureus / Q000276:immunology; D018089:Superantigens / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018122:B7-1 Antigen; D019013:CD40 Antigens; D000949:Histocompatibility Antigens Class II; D008562:Membrane Glycoproteins; D018089:Superantigens; D023201:CD40 Ligand