Follow-up of the process of diapedesis through stratified epithelium of the palatine tonsil (gut-associated lymphatic tissue or GALT) (human)

Stain: (A, C) Azan and (B, D) anti-keratin-antibody and immunoperoxidase staining using diaminobenzidin (DAB) on frozen section, counterstained with hematoxylin. (1) (keratinized) stratified squamous epithelial cells. (2) between desquamated epithelial cells the spaces are filled with infiltrated lymphocytes. (3) lymphatic follicles and (4) diffuse lymphocyte areas. Due to diapedesis and infiltration of lymphocytes (and monocytes) the epithelial cells get desquamated. The resulting intercellular spaces are dilated and filled with accumulations of lymphocytes and monocytes. From A to D there is a variable rate of loosening of the epithelial layer. The lymphocytes can even reach the outside of the epithelial lining as shown in (C). Functional active squamous epithelial cells still express keratin activity (B, D) in contrast to large amounts of flattened ones without any expression (B-1a), corresponding to the amorphous red-stained structures in Azan-stained sections (A-1a).