Initial lymphatics are present in the loose areolar connective tissue of the golden hamster's cheek pouch

Abstract

The immunologically privileged status of the hamster cheek pouch has been attributed to both the loose, areolar connective tissue that lines the pouch and to the lack of lymphatics in it. Although early reports described an absence of demonstrable lymphatics by classical histologic and lymphangiographic methods, issue has been taken recently as to whether the cheek pouch is alymphatic. We became interested in this issue accidentally during a study of microembolic microvascular injury. Our results, which were obtained by the coordinated use of intravital, light, and transmission electron microscopy, showed that a small population of initial lymphatics are present in the loose, areolar connective tissue. The areal density of initial lymphatics in 12 cheek pouches averaged 1.5 lymphatics/cm 2 of pouch connective tissue. We conclude that the hamster cheek pouch is drained by a small population of initial lymphatics, the general paucity of which probably contributes to the delayed egress of antigens to regional lymph nodes.