Although a substantial amount is known about the cellular elements that compose the lymphoid and nonlymphoid components of the secondary lymphoid tissues , information concerning the signals that control the development of the tissues and that maintain the organized tissue microenvironment remain undefined .
although a substantial amount is known about the cellular elements that compose the lymphoid and nonlymphoid components of the secondary lymphoid tissues , information concerning the signals that control the development of the tissues and that maintain the organized tissue microenvironment remain undefined .
O O O O O O O O B-DNA_family_or_group I-DNA_family_or_group O O O O O O O O O B-tissue I-tissue I-tissue O O O O O O O O O O O O O O O O B-other_name I-other_name I-other_name O O O