title: IL-15, an immunomodulator of T cell responses in intracellular infection.
abstract: IL-15 is a novel cytokine with potent T cell growth factor activity. Here, we investigated the role of IL-15 in the human immune response to intracellular infection by studying patients leprosy. We found that IL-15 mRNA and protein were more strongly expressed in immunologically resistant tuberculoid patients than in with unresponsive and susceptible lepromatous patients. In vitro, Mycobacterium leprae induced IL-15 secretion from peripheral blood monocytes. Furthermore, rIL-15 by itself and in combination with rIL-2 or rIL-7 augmented PBMC proliferative responses to the pathogen. Although rIL-15 expanded the CD3-CD56+ (NK) subset, rIL-15 combined with M. leprae induced the expansion of CD3+CD56+ T cells. Immunohistologic analysis of leprosy skin lesions indicated that the frequency of CD56+ cells was greatest in the group of patients with high IL-15 expression, and that >90% of the CD56+ cells in lesions were CD3+ T cells. Therefore, IL-15 augments the local T cell response to human intracellular pathogen.
authors.affiliation: Division of Dermatology, University of California School of Medicine, Los Angeles 90095, USA.
authors.forename: D
authors.initials: D
authors.lastname: Jullien
authors.forename: P A
authors.initials: PA
authors.lastname: Sieling
authors.forename: K
authors.initials: K
authors.lastname: Uyemura
authors.forename: N D
authors.initials: ND
authors.lastname: Mar
authors.forename: T H
authors.initials: TH
authors.lastname: Rea
authors.forename: R L
authors.initials: RL
authors.lastname: Modlin
mesh_terms: D003593:Cytoplasm / Q000382:microbiology*; D006801:Humans; D019409:Interleukin-15 / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology* / Q000627:therapeutic use*; D007918:Leprosy / Q000145:classification / Q000276:immunology* / Q000628:therapy*; D009000:Monocytes / Q000378:metabolism; D009166:Mycobacterium leprae / Q000276:immunology / Q000472:pathogenicity; D012333:RNA, Messenger / Q000032:analysis; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology*
chemical_list: D019409:Interleukin-15; D012333:RNA, Messenger