|Budget Amount *help
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
The T cell activation requires occupancy of T cell antigen receptors (TCR) by antigenic peptide presented by Major Histocompatibility Complex (MHC) and engagement of costimulatory molecules by appropriate ligands. We were especially interested in the mechanisms of antigen presentation by antigen presenting cells (APC). To address this issue, we started to identify human chemokine receptors expressed in professional APC, dendritic cells (DC), and to clarify the involvement of chemokine receptors in antigen presentation. Several investigators reported the expression of various chemokine receptors in DC at message level. To verify these observation at protein level, we established monoclonal antibodies to a panel of C-C and C-X-C type chemokine receptors. All antibodies have been characterized whether or not inhibit ligand-induced Ca mobilization. All of them were shown to immunoprecipitate appropriate receptor molecules from physiological blood cells. We could show expression of CCR-1, CCR-3, CCR-5, CCR-6, CCR-7 and CXCR-4 in DC by fiowcytometric analysis. Of monoclonal antibodies, those amtibodies of neutralizing character against human CCR-1 and CCR-3 could strongly inhibit ligand-induced chemotaxis of DC in trans-well migration analysis, which indicates RANTES, a ligand common to CCR-1 and CCR-3 was a major chmoattractant for DC. Inhibition of DC-expressed CCR-1 and CCR-3 resulted, unexpectedly, in inhibition of allogeneic T cell stimulation by DC. The reason for inhibition may be several fold, but the most striking phenomenon observed was that DC whose CCR-1 and CCR-3 were blocked were unable to mount heterotypic aggregation with target T cells required for mounting the contact of TCR and peptide on MHC.