Abstract
After a primary injection of horseradish peroxidase into the footpads of rabbits, the specific antibody reaction in popliteal lymph nodes was first seen in plasma cells of medullary cords and, later, in lymphoblasts of germinal centers in the cortex. During the late primary or early secondary response, the reaction also became positive in reticular cells and lymphocytes. Specific antibodies were also present in the intercellular spaces between lymphocytes (reticulum) in the lymphoid follicles and in globules distributed throughout the lymph node. Two weeks following a primary injection of the antigen, many plasma cells containing the specific antibody were located in proximity of macrophages and reticular cells. The phagolysosomes of many macrophages and reticular cells became antibody-positive at about the same time. Double staining procedures were developed by which the antigen and antibody and the antigen or antibody and acid phosphatase (lysosomes) could be visualized in the same tissue section.