Role of Rabbit Gut-Associated Lymphoid Tissue in Cell Replication. The Follicular Cortex as Primary Germinative Site ∗

Abstract

Summary

As shown by in vitro labeling techniques, the rabbit appendix and sacculus rotundus contained a higher number of cells in DNA synthesis than any other lymphoid organ examined. The bone marrow alone had a higher number of labeled cells. When labeled in vivo, gut-associated lymphoid organs of the rabbit contained a high number of cells in DNA synthesis. The follicles in these organs were distinguished from follicles of peripheral lymphoid tissue by separation into follicular cortex and medulla. The cortex contained large blastoid cells with a high labeling index; the medulla consisted primarily of small darker cells with a low labeling index. These findings support the hypothesis that the gut-associated lymphoid organs in the rabbit expand the lymphocyte population by rapid proliferation, and may play a role as primary lymphoid organs.