title: Possible involvement of T cell co-stimulation in pustulosis palmaris et plantaris via the induction of inducible co-stimulator in chronic focal infections.
abstract: BACKGROUND
  Inducible co-stimulator (ICOS) is a co-stimulatory receptor on activated T cells that provides the signals needed for Th1 and Th2 responses via its interaction with B7h. Chronic focal infections are closely related to pustulosis palmaris et plantaris (PPP), but the involvement of ICOS in PPP has not been clarified.
  
  
  OBJECTIVE
  To investigate the effectiveness of treatments for focal infections on PPP skin lesions and the involvement of ICOS-positive T cells at focal infection sites in the tonsils and in PPP lesional skin.
  
  
  METHODS
  In patients that had undergone a tonsillectomy or dental treatment, the clinical activities of PPP, both the skin lesions and pustulotic arthro-osteitis were followed for over 2 years. The expressions of ICOS and various other activation markers on T cells were examined in tonsil tissue from both PPP patients and non-PPP patients, and the expression levels in peripheral blood were also evaluated in PPP patients and healthy donors. ICOS-positive T cells and B7h expression in PPP and normal skin were examined immunohistochemically.
  
  
  RESULTS
  The above treatments for focal infections led to a dramatic and persistent improvement in the PPP skin lesions and pustulotic arthro-osteitis. The expression of ICOS, but not of other activation markers, was higher in tonsil tissues from PPP patients than in tonsil tissues from non-PPP patients. B7h was upregulated without numerous ICOS-positive T cell infiltrates in the skin lesions.
  
  
  CONCLUSIONS
  The activation of T cells via ICOS co-stimulation in focal infections likely triggers the skin and skeletal inflammation associated with PPP, resulting in tissue damage.
authors.affiliation: Department of Oral and [corrected] Maxillofacial Surgery, Tokyo Women's Medical University School of Medicine, Tokyo 162-8666, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Sakiyama
authors.forename: Satomi
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Umberto
authors.initials: U
authors.lastname: Dianzani
authors.forename: Hideki
authors.initials: H
authors.lastname: Ogiuchi
authors.forename: Makoto
authors.initials: M
authors.lastname: Kawashima
authors.forename: Takehiko
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Junji
authors.initials: J
authors.lastname: Yagi
mesh_terms: D000328:Adult; D000368:Aged; D015703:Antigens, CD / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D060890:B7-H1 Antigen; D015415:Biomarkers / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D060889:Inducible T-Cell Co-Stimulator Protein; D008297:Male; D008875:Middle Aged; D010510:Periodontal Diseases / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D011565:Psoriasis / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D017192:Skin Diseases, Bacterial / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D014069:Tonsillitis / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D060890:B7-H1 Antigen; D015415:Biomarkers; C423236:CD274 protein, human; C556692:ICOS protein, human; D060889:Inducible T-Cell Co-Stimulator Protein