The secondary lymphoid tissues are located at strategic sites where foreign antigens can be efficiently brought together with immune system regulatory and effector cells .
the secondary lymphoid tissues are located at strategic sites where foreign antigens can be efficiently brought together with immune system regulatory and effector cells .
O B-tissue I-tissue I-tissue O O O O O O B-protein_family_or_group I-protein_family_or_group O O O O O O O O O O O O O