Activation of T lymphocytes requires the combined signaling of the T cell receptor and costimulatory molecules such as CD28 .
activation of t lymphocytes requires the combined signaling of the t cell receptor and costimulatory molecules such as cd28 .
O O B-cell_type I-cell_type O O O O O O B-protein_family_or_group I-protein_family_or_group I-protein_family_or_group O B-protein_family_or_group I-protein_family_or_group O O B-protein_molecule O