title: Depletion of CD4+ T cells precipitates immunopathology in immunodeficient mice infected with a noncytocidal virus.
abstract: IFN-gamma-deficient (IFN-gamma(-/-)) mice inoculated with intermediate doses of a slowly replicating strain of lymphocytic choriomeningitis virus become chronically infected. In such mice a hypercompensated CTL response is observed that partially controls virus replication. Here we have investigated whether CD4(+) Th cells are required to establish and maintain this new equilibrium. The absence of IFN-gamma does not impair the generation of IL-2-producing CD4(+) cells, and depletion of these cells precipitates severe CD8(+) T cell-mediated immunopathology in IFN-gamma(-/-) mice, indicating an important role of CD4(+) T cells in preventing this syndrome. Analysis of organ virus levels revealed a further impairment of virus control in IFN-gamma(-/-) mice following CD4(+) cell depletion. Initially the antiviral CTL response did not require CD4(+) cells, but with time an impaired reactivity toward especially the glycoprotein 33--41 epitope was noted. Enumeration of epitope-specific (glycoprotein 33--41 and nucleoprotein 396--404) CD8(+) T cells by use of tetramers gave similar results. Finally, limiting dilution analysis of CTL precursors reveal an impaired capacity to sustain this population in CD4(+)-depleted mice, especially in mice also deficient in IFN-gamma. Thus, our findings disclose that T cell help is required to sustain the expanded CTL precursor pool required in IFN-gamma(-/-) mice. This interpretation is supported by mathematical modeling that predicts an increased requirement for help in IFN-gamma(-/-) hosts similar to what is found with fast replicating virus strains in normal hosts. Thus, the functional integrity of CD8(+) effector T cells is one important factor influencing the requirement for T cell help during viral infection.
authors.affiliation: Institute of Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: J P
authors.initials: JP
authors.lastname: Christensen
authors.forename: C
authors.initials: C
authors.lastname: Bartholdy
authors.forename: D
authors.initials: D
authors.lastname: Wodarz
authors.forename: A R
authors.initials: AR
authors.lastname: Thomsen
mesh_terms: D000208:Acute Disease; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology / Q000821:virology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000473:pathology / Q000821:virology; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D007371:Interferon-gamma / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D018655:Lymphocyte Count; D008212:Lymphocyte Depletion; D008216:Lymphocytic Choriomeningitis / Q000235:genetics / Q000276:immunology* / Q000473:pathology*; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology*; D008231:Lymphopenia / Q000235:genetics / Q000276:immunology* / Q000473:pathology* / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018448:Models, Immunological; D013234:Stem Cells / Q000276:immunology / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000821:virology
chemical_list: D018984:Epitopes, T-Lymphocyte; D007371:Interferon-gamma