Factors of tonsillar involution: age-dependent changes in B-cell activation and Langerhans' cell density.

Incorporation of radioactive thymidine as well as morphological and autoradiographical investigations performed with isolated B and T lymphocytes of the tonsil show that first of all B cells are activated or proliferating. The combination of autoradiography with cytochemistry was the only means of detecting a few activated T cells. With increasing age the number of activated B cells decreases. A reduced number of Langerhans' cells acting as antigen receptors in the epithelium of the crypt is assumed to be one cause of this phenomenon. Tonsillar involution originates from both a decline in the antigen receptors and in the depletion of B-cell activation. Malfunctions in these processes give rises to pathogenic factors in chronic tonsillitis.