title: Detection by flow cytometry of ESAT-6- and PPD-specific circulating CD4+ T lymphocytes as a diagnostic tool for tuberculosis.
abstract: BACKGROUND
  The identification of mycobacteria represents the gold standard in the diagnosis of tuberculosis (TB), but it is not applicable in all patients, and immunological tests, such as the tuberculin skin test (TST), are not specific and sensitive enough.
  
  
  METHODS
  By flow cytometry, we measured the CD4 T-cell response to purified protein derivative (PPD) and early secretory antigenic target-6 (ESAT-6) protein using the intracellular cytokine staining technique on whole blood samples obtained from active TB (n = 16), latent TB (n = 17), Bacille Calmette-Guérin (BCG)-vaccinated (n = 11) and healthy (n = 10) donors. All the patients were also tested with conventional TST.
  
  
  RESULTS
  The identification by flow cytometry of PPD-specific T lymphocytes upon antigen stimulation of whole blood enables the discrimination of active TB, latent TB and BCG-vaccinated subjects from healthy individuals, whereas the ESAT-6 response discriminated active TB from healthy and BCG-vaccinated individuals. Moreover, this test enables identification of active TB patients who were negative on TST and to distinguish between TB and non-typical mycobacteria TB infections.
  
  
  CONCLUSIONS
  The identification by flow cytometry of antigen-specific T lymphocytes upon antigen stimulation of whole blood has a better positive predictive value than TST, and could represent a further tool in the diagnosis of TB infection.
authors.affiliation: Center for High Research DENOthe, University of Florence, Florence, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cosmi
authors.forename: Laura
authors.initials: L
authors.lastname: Maggi
authors.forename: Veronica
authors.initials: V
authors.lastname: Santarlasci
authors.forename: Francesco
authors.initials: F
authors.lastname: Liotta
authors.forename: Francesca
authors.initials: F
authors.lastname: Frosali
authors.forename: Roberta
authors.initials: R
authors.lastname: Angeli
authors.forename: Marcello
authors.initials: M
authors.lastname: Mazzetti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Vultaggio
authors.forename: Andrea
authors.initials: A
authors.lastname: Matucci
authors.forename: Enrico
authors.initials: E
authors.lastname: Maggi
authors.forename: Sergio
authors.initials: S
authors.lastname: Romagnani
authors.forename: Francesco
authors.initials: F
authors.lastname: Annunziato
mesh_terms: D000942:Antigens, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D008297:Male; D014373:Tuberculin / Q000276:immunology*; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000096:biosynthesis
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D014373:Tuberculin; D014409:Tumor Necrosis Factor-alpha