title: Deposition of membrane attack complex in cutaneous lesions of lupus erythematosus.
abstract: BACKGROUND
  The membrane attack complex (MAC; C5b-9) localizes in the basement membrane zone (BMZ) of cutaneous lesions from patients with lupus erythematosus (LE) and has been implicated in the pathogenesis of this disease.
  
  
  OBJECTIVE
  Our purpose was to compare the frequency of MAC deposition with that of immunoglobulin and C3 deposition (lupus band).
  
  
  METHODS
  We studied 56 skin biopsy specimens from 42 patients with LE by direct immunofluorescence.
  
  
  RESULTS
  MAC was deposited in a granular pattern at the BMZ in 29 of 38 biopsy specimens (76%) from lesional skin; 5 of 38 specimens (13%) had focal or weak segmental deposition and 4 of 38 (11%) were negative. In contrast, IgG, IgM, IgA, and C3 were detected in 16 of 38 specimens (42%), 30 of 38 (79%), 4 of 38 (11%), and 22 of 38 (58%), respectively. None of the uninvolved skin biopsy specimens was MAC positive, although 4 of 18 (22%), 5 of 18 (28%), 1 of 18 (6%), and 2 of 18 (11%) were positive for IgG, IgM, IgA, and C3, respectively.
  
  
  CONCLUSIONS
  MAC deposition in lesional skin appears to be a relatively sensitive and specific marker for cutaneous LE and may be useful as an adjunct to the "lupus band" test.
authors.affiliation: Immunodermatology Laboratory, Mayo Clinic, Rochester, MN 55905.
authors.forename: K F
authors.initials: KF
authors.lastname: Helm
authors.forename: M S
authors.initials: MS
authors.lastname: Peters
mesh_terms: D001485:Basement Membrane / Q000378:metabolism / Q000473:pathology; D003176:Complement C3 / Q000378:metabolism; D015938:Complement Membrane Attack Complex / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism; D007075:Immunoglobulin M / Q000378:metabolism; D008178:Lupus Erythematosus, Cutaneous / Q000378:metabolism* / Q000473:pathology; D008179:Lupus Erythematosus, Discoid / Q000378:metabolism* / Q000473:pathology; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism* / Q000473:pathology; D012680:Sensitivity and Specificity; D012867:Skin / Q000378:metabolism* / Q000473:pathology; D013194:Staining and Labeling
chemical_list: D003176:Complement C3; D015938:Complement Membrane Attack Complex; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M