title: Effect of the novel influenza A (H1N1) virus in the human immune system.
abstract: BACKGROUND
  The pandemic by the novel H1N1 virus has created the need to study any probable effects of that infection in the immune system of the host.
  
  
  RESULTS
  Blood was sampled within the first two days of the presentation of signs of infection from 10 healthy volunteers; from 18 cases of flu-like syndrome; and from 31 cases of infection by H1N1 confirmed by reverse RT-PCR. Absolute counts of subtypes of monocytes and of lymphocytes were determined after staining with monoclonal antibodies and analysis by flow cytometry. Peripheral blood mononuclear cells (PBMCs) were isolated from patients and stimulated with various bacterial stimuli. Concentrations of tumour necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-18, interferon (FN)-alpha and of IFN-gamma were estimated in supernatants by an enzyme immunoassay. Infection by H1N1 was accompanied by an increase of monocytes. PBMCs of patients evoked strong cytokine production after stimulation with most of bacterial stimuli. Defective cytokine responses were shown in response to stimulation with phytohemagglutin and with heat-killed Streptococcus pneumoniae. Adaptive immune responses of H1N1-infected patients were characterized by decreases of CD4-lymphocytes and of B-lymphocytes and by increase of T-regulatory lymphocytes (Tregs).
  
  
  CONCLUSIONS
  Infection by the H1N1 virus is accompanied by a characteristic impairment of the innate immune responses characterized by defective cytokine responses to S.pneumoniae. Alterations of the adaptive immune responses are predominated by increase of Tregs. These findings signify a predisposition for pneumococcal infections after infection by H1N1 influenza.
authors.affiliation: 4th Department of Internal Medicine, University of Athens, Medical School, Greece, Athens, Greece. giamarel@ath.forthnet.gr
authors.forename: Evangelos J
authors.initials: EJ
authors.lastname: Giamarellos-Bourboulis
authors.forename: Maria
authors.initials: M
authors.lastname: Raftogiannis
authors.forename: Anastasia
authors.initials: A
authors.lastname: Antonopoulou
authors.forename: Fotini
authors.initials: F
authors.lastname: Baziaka
authors.forename: Pantelis
authors.initials: P
authors.lastname: Koutoukas
authors.forename: Athina
authors.initials: A
authors.lastname: Savva
authors.forename: Theodora
authors.initials: T
authors.lastname: Kanni
authors.forename: Marianna
authors.initials: M
authors.lastname: Georgitsi
authors.forename: Aikaterini
authors.initials: A
authors.lastname: Pistiki
authors.forename: Thomas
authors.initials: T
authors.lastname: Tsaganos
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Pelekanos
authors.forename: Sofia
authors.initials: S
authors.lastname: Athanassia
authors.forename: Labrini
authors.initials: L
authors.lastname: Galani
authors.forename: Efthymia
authors.initials: E
authors.lastname: Giannitsioti
authors.forename: Dimitra
authors.initials: D
authors.lastname: Kavatha
authors.forename: Flora
authors.initials: F
authors.lastname: Kontopidou
authors.forename: Maria
authors.initials: M
authors.lastname: Mouktaroudi
authors.forename: Garyfallia
authors.initials: G
authors.lastname: Poulakou
authors.forename: Vissaria
authors.initials: V
authors.lastname: Sakka
authors.forename: Periklis
authors.initials: P
authors.lastname: Panagopoulos
authors.forename: Antonios
authors.initials: A
authors.lastname: Papadopoulos
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Kanellakopoulou
authors.forename: Helen
authors.initials: H
authors.lastname: Giamarellou
mesh_terms: D056704:Adaptive Immunity / Q000276:immunology; D000328:Adult; D001772:Blood Cell Count; D016207:Cytokines / Q000097:blood; D003710:Demography; D005260:Female; D006801:Humans; D007107:Immune System / Q000821:virology*; D007113:Immunity, Innate / Q000276:immunology; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000097:blood / Q000150:complications / Q000821:virology; D008297:Male; D011014:Pneumonia / Q000097:blood / Q000150:complications / Q000821:virology; D013997:Time Factors
chemical_list: D016207:Cytokines