[Genesis and differentiation of interdigitating cells in human lymph nodes (author's transl)]

Genesis and differentiation of so-called interdigitating cells (IDC) of secondary lymphatic organs are reported by electron microscopic investigation of human lymph nodes in different cutaneous disorders. The formation of these cells apparently take place by differentiation of monocytic cells, in which a cyto-morphological transition into typical IDC--showing characteristic tubulo-vesicular structures--has been observed. Therefore, the IDC apparently represent a special structural and functional form of the monocytic-macrophagic system in lymph nodes and spleen. A hypertrophic reaction of these cells obviously takes place parallel with a decrease of electron density of the cytoplasm as well as an increase of the interdigitating cytoplasmic processes. Differentiated IDC also contain numerous T-lymphocytes within of the cytoplasm, which are partly situated quite near of the nucleus. However, the enclosed lymphocytes show no ultrastructural alterations. Therefore such "emperipolesis" may probably be a normal histo-morphological phenomenon of the lymph nodes whereas in immuno-pathological conditions an accumulation of tubulovesicular structures as well as a decrease of the cytomorphological contacts between IDC and T-lymphocytes has been observed.