title: Immunosuppression by CD4+ regulatory T cells induced by chronic retroviral infection.
abstract: Normal levels of CD4(+) regulatory T cells are critical for the maintenance of immunological homeostasis and the prevention of autoimmune diseases. However, we now show that the expansion of CD4(+) regulatory T cells in response to a chronic viral infection can lead to immunosuppression. Mice persistently infected with Friend retrovirus develop approximately twice the normal percentage of splenic CD4(+) regulatory T cells and lose their ability to reject certain tumor transplants. The role of CD4(+) regulatory T cells was demonstrated by the transmission of immunosuppression to uninfected mice by adoptive transfers of CD4(+) T cells. CD4(+) T cells from chronically infected mice were also immunosuppressive in vitro, inhibiting the generation of cytolytic T lymphocytes in mixed lymphocyte cultures. Inhibition occurred at the level of blast-cell formation through a mechanism or mechanisms involving transforming growth factor-beta and the cell surface molecule CTLA-4 (CD152). These results suggest a possible explanation for HIV- and human T cell leukemia virus-I-induced immunosuppression in the absence of T cell depletion.
authors.affiliation: Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
authors.forename: M
authors.initials: M
authors.lastname: Iwashiro
authors.forename: R J
authors.initials: RJ
authors.lastname: Messer
authors.forename: K E
authors.initials: KE
authors.lastname: Peterson
authors.forename: I M
authors.initials: IM
authors.lastname: Stromnes
authors.forename: T
authors.initials: T
authors.lastname: Sugie
authors.forename: K J
authors.initials: KJ
authors.lastname: Hasenkrug
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D005622:Friend murine leukemia virus / Q000502:physiology*; D007108:Immune Tolerance; D051379:Mice; D008810:Mice, Inbred C57BL; D012192:Retroviridae Infections / Q000276:immunology*