Localization of 125I-Labeled Antigen in Germinal Centers of Mouse Spleen: Histologic and Ultrastructural Autoradiographic Studies of the Secondary Immune Reaction

Abstract

Histologic and ultrastructural studies were carried out on the process of the localization of antigen in splenic germinal centers during the secondary immune reaction in mice. The magnitude and regularity of the developed plasma membrane infoldings of antigen-retaining reticular cells in germinal centers are described. The key finding was that these specifically developed plasma membrane infoldings are degraded during the early intervals of the secondary response. This response occurred in conjunction with a loss of label and an apparent loss of function of the existing antigen-trapping mechanism in splenic germinal centers. We suggest that the described cytotoxic sequelae could be a result of complement fixation and that such a regulatory mechanism would be essential to prevent further contact of immunologically competent cells with antigen, while clearing the centers for their development against other antigens. A conformity of vesicles was observed in the cytoplasm of the parenchymal cells of the germinal centers and in the plasma membrane infoldings of the antigen-retaining reticular cells.