title: Macrophage cathepsin L, a factor in the erosion of subchondral bone in rheumatoid arthritis.
abstract: OBJECTIVE
  To test the hypothesis that the proteinase cathepsin L is involved in the subchondral bone lesions found in chronic rheumatoid arthritis (RA).
  
  
  METHODS
  The medial tibial plateaus from 4 control cases and 30 patients diagnosed as having end-stage RA were examined immunochemically for cathepsin L.
  
  
  RESULTS
  RA lesions include large groups of mononuclear cells, many of which are rich in cathepsin L. Since these mononuclear cells contained the CD68 glycoprotein and, in the electron microscope, displayed an irregular cell surface, cytoplasmic vacuoles, lysosomes, and phagosomes, they were identified as belonging to the macrophage family. The lesions were classified into 2 main patterns, both displaying these cathepsin L-rich cells, which, in at least 1 of the 2, were closely associated with bone degradation.
  
  
  CONCLUSIONS
  The cathepsin L-rich macrophages are sufficiently numerous to be considered a major factor in producing the erosion of subchondral bone found in chronic RA lesions.
authors.affiliation: Shriners Hospital for Children, McGill University, Montreal, Quebec, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Iwata
authors.forename: J S
authors.initials: JS
authors.lastname: Mort
authors.forename: H
authors.initials: H
authors.lastname: Tateishi
authors.forename: E R
authors.initials: ER
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000473:pathology*; D001842:Bone and Bones / Q000201:enzymology / Q000648:ultrastructure; D002358:Cartilage, Articular / Q000033:anatomy & histology / Q000737:chemistry / Q000201:enzymology; D056668:Cathepsin L; D002403:Cathepsins / Q000276:immunology / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000502:physiology; D010450:Endopeptidases; D004792:Enzyme Precursors / Q000502:physiology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged
chemical_list: D004792:Enzyme Precursors; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L