This observation prompted us to postulate that signal 2 ( costimulatory signal ) alone without signal 1 ( TCR signal ) can activate T cells .
this observation prompted us to postulate that signal 2 ( costimulatory signal ) alone without signal 1 ( tcr signal ) can activate t cells .
O O O O O O O B-other_name I-other_name O B-other_name I-other_name O O O B-other_name I-other_name O B-protein_family_or_group O O O O B-cell_type I-cell_type O