title: Interdigitating reticulum cells in lymph nodes of Sézary syndrome. Freeze-fracture and ultrathin-section morphology.
abstract: Lymph nodes with extensive leukemic infiltration from three patients with the Sézary syndrome were examined in ultrathin sections and in freeze-fracture replicas. Sézary cells (SC) and interdigitating reticulum cells (IDC) were the predominant cell types in the lymph nodes. Both were closely connected with each other by apparently interdigitating cytoplasmic processes. The projections between these cells were, in the main, processes from the IDC. In freeze-fracture replicas these cellular processes did not appear as interdigitations but were more bubble-like, and for this reason these cells are imprecisely described by the term "interdigitating." The SC were seen to possess only short cytoplasmic processes. The frequent polar grouping of cell organelles in SC in the region of the contact zone with IDC and the high organelle content of IDC ('activated IDC') could be the morphologic expression of intense interaction between IDC and SC. IDC displayed three features in freeze-fracture which are not specific to the Sézary syndrome, but should be applicable to IDC in general: (1) they exhibited an approximately equal density of intramembrane particles in both the E-face and the P-face, (2) some of the intramembrane particles in the P-face were assembled in clusters and (3) the surface showed bubble-like formations of the cytoplasmic processes. On the basis of these properties it was possible to distinguish IDC from macrophages and lymphocytes in freeze-fracture replicas.
mesh_terms: D000938:Antigen-Presenting Cells / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D003713:Dendritic Cells / Q000648:ultrastructure*; D005614:Freeze Fracturing; D006801:Humans; D008198:Lymph Nodes / Q000648:ultrastructure*; D008214:Lymphocytes / Q000648:ultrastructure*; D012751:Sezary Syndrome / Q000473:pathology*