IL-15, an immunomodulator of T cell responses in intracellular infection

• Published in: The Journal of immunology (1950) Vol. 158; no. 2; pp. 800 - 806
• Main Authors: Jullien, D, Sieling, PA, Uyemura, K, Mar, ND, Rea, TH, Modlin, RL
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.01.1997
• Subjects: Cytoplasm - microbiology; Humans; Interleukin-15 - biosynthesis; Interleukin-15 - genetics; Interleukin-15 - pharmacology; Interleukin-15 - therapeutic use; Leprosy - classification; Leprosy - immunology; Leprosy - therapy; Monocytes - metabolism; Mycobacterium leprae; Mycobacterium leprae - immunology; Mycobacterium leprae - pathogenicity; RNA, Messenger - analysis; T-Lymphocytes - drug effects; T-Lymphocytes - immunology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.158.2.800

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.