Serum proteins in human squamous epithelium.

A new immunoperoxidase staining technique of high specificity (the labelled antigen method) has been used for the detection of serum proteins in the epithelium of human skin and mucous membranes. The majority of specimens contain cells showing strong diffuse intracellular staining. These cells usually lie in the upper mid-zone of the epithelium and are often characterized by vacuolated or pyknotic nuclei. Double immunoenzymatic labelling (using alkaline phosphatase and peroxidase) showed that the different proteins are usually present in the same cells. A less frequent pattern of staining took the form of delicate strands of intercellular IgG. Samples from a wide range of skin diseases were studied, but no clear relationship between positive epithelial staining and disease states was apparent. It is suggested that serum proteins may enter epithelial cells by passive diffusion, and attention is drawn to other instances (e.g. in the central nervous system and lymphoid tissue) where similar phenomena have been observed by immunoenzymatic staining techniques.