title: Interleukin-10- and transforming growth factor β-independent regulation of CD8⁺ T cells expressing type 1 and type 2 cytokines in human lymphatic filariasis.
abstract: Lymphatic filariasis is known to be associated with diminished CD4⁺ Th1 and elevated CD4⁺ Th2 responses to parasite-specific antigens. The roles of cytokine-expressing CD8⁺ T cells in immune responses to filarial infections are not well defined. To study the roles of CD8⁺ T cells expressing type 1, type 2, and type 17 cytokines in filarial infections, we examined the frequencies of these cells in clinically asymptomatic, patently infected (INF) individuals, directly ex vivo and in response to parasite or nonparasite antigens; these frequencies were compared with the results for individuals with filarial lymphedema (i.e., clinical pathology [CP]) and those without active infection or pathology (i.e., endemic normal [EN]). INF individuals exhibited significant decreases in the frequencies of CD8⁺ T cells expressing tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin-22 (IL-22) at baseline and/or in response to filarial antigens, compared with CP and EN individuals. In contrast, the same individuals exhibited significant increases in the frequencies of CD8⁺ T cells expressing IL-4, IL-5, IL-9, IL-13, and IL-21, compared with CP and/or EN individuals. Curative treatment resulted in significantly increased frequencies of CD8⁺ T cells expressing IL-2 and significantly decreased frequencies of CD8⁺ T cells expressing type 2 cytokines. Finally, the regulation of these responses appears to be independent of IL-10 and transforming growth factor β (TGF-β), since blockade of IL-10 or TGF-β signaling did not significantly alter the frequencies of type 1 or type 2 cytokine-expressing CD8⁺ T cells. Our findings suggest that alterations in the frequencies of cytokine-expressing CD8⁺ T cells are characteristic features of lymphatic filarial infections.
authors.affiliation: National Institutes of Health-International Center for Excellence in Research, Chennai, India.
authors.forename: Rajamanickam
authors.initials: R
authors.lastname: Anuradha
authors.affiliation: National Institutes of Health-International Center for Excellence in Research, Chennai, India.
authors.forename: Parakkal Jovvian
authors.initials: PJ
authors.lastname: George
authors.affiliation: National Institute for Research in Tuberculosis, Chennai, India.
authors.forename: Paul
authors.initials: P
authors.lastname: Kumaran
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
authors.affiliation: National Institutes of Health-International Center for Excellence in Research, Chennai, India Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA sbabu@mail.nih.gov.
authors.forename: Subash
authors.initials: S
authors.lastname: Babu
mesh_terms: D000328:Adult; D000368:Aged; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism*; D004605:Elephantiasis, Filarial / Q000276:immunology*; D006801:Humans; D016753:Interleukin-10 / Q000502:physiology*; D008875:Middle Aged; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D016207:Cytokines; D016212:Transforming Growth Factor beta; D016753:Interleukin-10