One signal can be delivered by the antigen-specific T-cell receptor , and the second signal is provided by the costimulatory molecule ( s ) delivered by the antigen-presenting cell .
one signal can be delivered by the antigen-specific t-cell receptor , and the second signal is provided by the costimulatory molecule ( s ) delivered by the antigen-presenting cell .
O O O O O O O B-protein_molecule I-protein_molecule I-protein_molecule O O O O O O O O O O O O O O O O O B-cell_type I-cell_type O