title: Distribution of PD-1+ lymphocytes in reactive lymphadenopathies.
abstract: OBJECTIVE
  Programmed death-1 (PD-1) is physiologically expressed by germinal center (GC)-associated helper T cells. It has been proposed that an increase in PD-1+ cells outside GC could indicate pattern I angioimmunoblastic T-cell lymphoma (AITL).
  
  
  METHODS
  We studied the distribution of PD-1+ cells in reactive lymphadenopathies (LA), including HIV-associated and dermatopathic LA (n = 5, each), Castleman (n = 3), Kikuchi (n = 2) and Rosai-Dorfman diseases (n = 1), sarcoidoses (n = 7) and follicular hyperplasias (n = 8).
  
  
  RESULTS
  The highest concentrations of PD-1+ cells in GC were found in Castleman and Rosai-Dorfman diseases (mean 57 and 50% of total cells, respectively), and the lowest in HIV-associated LA (mean 6%). The highest proportions in paracortices were found in Castleman disease, and in HIV-associated and dermatopathic LA (mean 7, 3 and 2%, respectively). PD-1+ cells predominated in the pale zones of GC in follicular hyperplasia. In HIV-associated LA, PD-1+ cells showed marked marginalization in the GC. No paracortical PD-1+ cells were found in sarcoidoses and Rosai-Dorfman disease.
  
  
  CONCLUSIONS
  The varying distribution of PD-1+ cells in defined LA might indicate a functional relevance of these cells in the respective entities. Since increased numbers of PD-1+ cells outside GC are observed in various LA, this finding might not be entirely specific for pattern I AITL.
authors.affiliation: Institute of Pathology, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: Simone
authors.initials: S
authors.lastname: Muenst
authors.forename: Stephan
authors.initials: S
authors.lastname: Dirnhofer
authors.forename: Alexandar
authors.initials: A
authors.lastname: Tzankov
mesh_terms: D015703:Antigens, CD / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins / Q000276:immunology*; D005871:Castleman Disease / Q000473:pathology; D015618:Histiocytosis, Sinus / Q000473:pathology; D006801:Humans; D007119:Immunoblastic Lymphadenopathy / Q000473:pathology; D008206:Lymphatic Diseases / Q000145:classification* / Q000473:pathology*; D008214:Lymphocytes / Q000473:pathology*; D061026:Programmed Cell Death 1 Receptor; D012507:Sarcoidosis / Q000473:pathology
chemical_list: D015703:Antigens, CD; D051017:Apoptosis Regulatory Proteins; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor