title: CD8 T cell-mediated killing of Cryptococcus neoformans requires granulysin and is dependent on CD4 T cells and IL-15.
abstract: Granulysin is located in the acidic granules of cytotoxic T cells. Although the purified protein has antimicrobial activity against a broad spectrum of microbial pathogens, direct evidence for granulysin-mediated cytotoxicity has heretofore been lacking. Studies were performed to examine the regulation and activity of granulysin expressed by CD8 T cells using Cryptococcus neoformans, which is one of the most common opportunistic pathogens of AIDS patients. IL-15-activated CD8 T cells acquired anticryptococcal activity, which correlated with the up-regulation of granulysin. When granules containing granulysin were depleted using SrCl(2,) or when the gene was silenced using 21-nt small interfering RNA duplexes, the antifungal effect of CD8 T cells was abrogated. Concanamycin A and EGTA did not affect the antifungal effect, suggesting that the activity of granulysin was perforin independent. Following stimulation by the C. neoformans mitogen, CD8 T cells expressed granulysin and acquired antifungal activity. This activity required CD4 T cells and was dependent upon accessory cells. Furthermore, IL-15 was both necessary and sufficient for granulysin up-regulation in CD8 T cells. These observations are most consistent with a mechanism whereby C. neoformans mitogen is presented to CD4 T cells, which in turn activate accessory cells. The resultant IL-15 activates CD8 T cells to express granulysin, which is responsible for antifungal activity.
authors.affiliation: Department of Medical Sciences, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Ling Ling
authors.initials: LL
authors.lastname: Ma
authors.forename: Jason C L
authors.initials: JC
authors.lastname: Spurrell
authors.forename: Jian Fei
authors.initials: JF
authors.lastname: Wang
authors.forename: Graham G
authors.initials: GG
authors.lastname: Neely
authors.forename: Slava
authors.initials: S
authors.lastname: Epelman
authors.forename: Alan M
authors.initials: AM
authors.lastname: Krensky
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Mody
mesh_terms: D000276:Adjuvants, Immunologic / Q000096:biosynthesis / Q000502:physiology; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000935:Antifungal Agents / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000382:microbiology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D002469:Cell Separation; D003455:Cryptococcus neoformans / Q000254:growth & development* / Q000276:immunology*; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D006801:Humans; D019409:Interleukin-15 / Q000502:physiology*; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D008213:Lymphocyte Activation / Q000276:immunology; D018942:Macrolides; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology; D008934:Mitogens / Q000494:pharmacology; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D015854:Up-Regulation / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D000945:Antigens, Differentiation, T-Lymphocyte; C075005:GNLY protein, human; D019409:Interleukin-15; D018942:Macrolides; D008562:Membrane Glycoproteins; D008934:Mitogens; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin; C036978:concanamycin A