Differentiation Pathway within Germinal Centers of Human Tonsils

Abstract

Tonsils are continuously exposed to antigenic stimulation and may therefore, under physiological conditions, represent a situation comparable to a steady-state immune response. The presence of large germinal centers and numerous plasma cells within these structures indicates that the lymphoreticular tissue at this site is involved in the production of humoral antibodies. It has been recognized that tonsillar germinal centers show a distinct polarity: densely packed, basophilic lymphoid cells, numerous mitotic figures, and many tingible bodies are grouped in the area opposite to the cryptic epithelium (“base”), while a more loosely populated zone is located towards the surface (“cap”) and covered by a rim of small lymphocytes and plasma cells. The extensive studies of Koburg [1, 2, 3, 4] on rabbit tonsils, using ³H-thymidine as a cell marker, have convincingly shown that (1) germinal center cells formed at the base migrate towards the cap, and (2) most lymphoid cells and small lymphocytes on the epithelial side of germinal centers originate from the latter. Preliminary results obtained in our laboratory on human tonsils are consisten with a similar flux of cells (H. P. Wagner and H. Cottier, unpublished results).