tertiary lymphoid tissues
constitute sites of the body where the elimination of antigen takes place. These sites comprise the “battlefield” on which the immune system defends the tissues from microbial invasion. These tissues, such as the skin and mucosal lining of the gastrointestinal, pulmonary, and genitourinary tracts, have direct contact with the external environment. Examples include the skin, gastrointestinal tract, lungs, and vagina.