Cell proliferation in the endolymphatic sac in situ after inner ear immunostimulation

Cell proliferation in the endolymphatic sac (ES) after immunostimulation was assessed immunohistochemically. Guinea pigs were employed as experimental animals and keyhole limpet hemocyanin was used as the antigen. After i.p. injection of 5-bromo-2'-deoxyuridine (BrdUrd), the BrdUrd+ cells were counted to assess the number of proliferating cells. In the secondary immune reaction of the ES, the IgG+ cell count in the perisaccular region was markedly increased on days 7-14. An increased number of BrdUrd+ cells was detected, peaking on day 3, and the localization of these cells in the ES was similar to that of the IgG+ cells. This suggests that some BrdUrd+ cells may differentiate into IgG- cells within the ES.