ABSTRACT
Lymph nodes have a well-defined architecture including sinuses, cortical, paracortical, and medullary regions (Fig. 1). Sinuses are potential spaces lined by sinus histiocytes which are professional macrophages (Fig. 2). Cortical areas of the lymph node contain lymphoid follicles which bring developing B lymphocytes into contact with antigen expressing follicular dendritic cells (Fig. 3). Naı¨ve B cells are concentrated in the dark staining mantle zone surrounding the germinal center (GC) (Fig. 3). These mantle zone lymphocytes are small to medium sized, have dense chromatin, and express surface immunoglobulin M (IgM) and immunoglobulin D (IgD).
