Optimal T cell activation requires two signals , one generated by TCR and another by the CD28 costimulatory receptor .
optimal t cell activation requires two signals , one generated by tcr and another by the cd28 costimulatory receptor .
B-other_name I-other_name I-other_name I-other_name O O O O O O O B-protein_family_or_group O O O O B-protein_molecule I-protein_molecule I-protein_molecule O