has_participant has participant has participant lymphocyte costimulation T cell costimulation GO:0031295 T cell co-stimulation T lymphocyte costimulation T-cell co-stimulation T-cell costimulation T-lymphocyte costimulation The process of providing, via surface-bound receptor-ligand pairs, a second, antigen-independent, signal in addition to that provided by the T cell receptor to augment T cell activation. biological_process positive regulation of T cell activation CD3D CD3G CD247 CD40LG HLA-DRA CCL19 CCL21