title: Expression of CTLA-4 (CD152) in peripheral blood T cells of children with influenza virus infection including encephalopathy in comparison with respiratory syncytial virus infection.
abstract: Influenza virus and respiratory syncytial virus (RSV) are the most common causes of acute severe respiratory infection in children during the winter. There have been few reports about peripheral blood T cell activation in vivo in influenza virus infection and conflicting results concerning peripheral blood T cells activation in RSV infection. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4, CD152) is a receptor present on T cells that plays a critical role in the down-regulation of antigen-activated immune responses. To clarify the status of peripheral blood T cells, we investigated intracellular CTLA-4 expression in T cells in patients with influenza virus and RSV infection. We collected blood samples from 15 patients with influenza virus infection, including three with complications of influenza virus-associated encephalopathy and 18 patients with RSV infection, as well as 44 healthy children. We determined the intracellular expression of CTLA-4 in CD4+ and CD8+ T cells by flow cytometry. There were no significant differences in the percentages of intracellular CTLA-4-positive CD4+ T cells and CD8+ T cells by age. The percentages of intracellular CTLA-4-positive CD4+ T cells in the patients with influenza virus infection were significantly higher than those in healthy children (P < 0.01). In particular, the patients with influenza virus-associated encephalopathy had sevenfold higher percentages of CTLA-4-positive CD4+ T cells than influenza patients without encephalopathy (P < 0.05). The patients with influenza virus-associated encephalopathy had increased percentages of CTLA-4-positive CD8+ cells at the acute stage in comparison with the convalescent stage and in control subjects (P < 0.01, respectively). RSV patients showed no increase in CTLA-4-positive CD4+ T cells or CD8+ T cells. The immunological status of peripheral T cell activation is substantially different in influenza virus infection and RSV infection. The patients with RSV infection did not show any increase in CTLA-4-positive peripheral blood T cells. There was a remarkable increase in intracellular CTLA-4 in CD4+ and CD8+ T cells in influenza virus-associated encephalopathy. Down-regulation of antigen-activated peripheral blood T cell activation might play an important role in the pathogenesis of influenza virus-associated encephalopathy and host defence against influenza virus infection.
authors.affiliation: Department of Pediatrics, Yamaguchi University School of Medicine, Yamaguchi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ayukawa
authors.forename: T
authors.initials: T
authors.lastname: Matsubara
authors.forename: M
authors.initials: M
authors.lastname: Kaneko
authors.forename: M
authors.initials: M
authors.lastname: Hasegawa
authors.forename: T
authors.initials: T
authors.lastname: Ichiyama
authors.forename: S
authors.initials: S
authors.lastname: Furukawa
mesh_terms: D000293:Adolescent; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000097:blood*; D001927:Brain Diseases / Q000150:complications / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood*; D007223:Infant; D007251:Influenza, Human / Q000150:complications / Q000276:immunology; D008297:Male; D009976:Orthomyxoviridae Infections / Q000150:complications / Q000276:immunology*; D018357:Respiratory Syncytial Virus Infections / Q000150:complications / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D007166:Immunosuppressive Agents