Applicability of imprints to immuno-ultrastructural studies of lymphoid tissues.

In order to evaluate the applicability of imprints to immuno-ultrastructural studies of lymphoid tissues, we compared distribution pattern and morphology of B cells, T cells, T-cell subsets, and follicular dendritic reticulum cells (DRC) at the light and ultrastructural level in imprints and sections of tonsils and lymph nodes. The surface antigenic profile of lymphoid cells was revealed with monoclonal antibodies in an avidin-biotin-peroxidase complex (ABC) method. Distribution of lymphoid cells in coherent areas of imprints recapitulated their disposition in sections of respective lymphoid tissues. Preservation of microanatomical relationships and ultrastructure of lymphoid cells in imprints allowed evaluation of associations and fine structural detail of lymphoid cells. Morphologic configurations of B cells in imprints, confined to round aggregates, were similar to fine structural morphology of B cells in mantle zones (MZ) and germinal centers (GC). Processes of DRCs in imprints formed conformations resembling their meshwork within follicles and mantled lymphoid cells. In imprints and sections, lymphocytes of cytotoxic/suppressor phenotype had a large amount of cytoplasm with many organelles. In contrast, cells of helper/inducer phenotype displayed a high nucleocytoplasmic (N/C) ratio and small numbers of organelles. Thus, imprints represent an easy, fast, and reliable method that lends itself to immunoultrastructural studies of lymphoid tissues.