Role of IL-15, IL-2, and their receptors in the development of T cell alveolitis in pulmonary sarcoidosis.
Recent data suggest that the newly discovered cytokine IL-15 cooperates with IL-2 in driving T cell-mediated immune responses. The aim of this study was to determine the role of IL-15 in the regulatory networks leading to the development of T cell alveolitis in the lung of patients with sarcoidosis. We demonstrated that alveolar macrophages (AMs) isolated from the bronchoalveolar lavage of patients with active sarcoidosis expressed IL-15 mRNA and membrane and cytoplasmic IL-15, while AMs from healthy subjects and patients with inactive sarcoidosis did not. Pulmonary CD4+ T cells from sarcoid patients were equipped with the IL-2R subunits, which are able to bind IL-15, i.e., the IL-2R beta/IL-2R gamma complex, and proliferated in response to IL-15. Interestingly, the T cell proliferation elicited by IL-15 was comparable with that determined by IL-2. Following the addition of graded amounts of IL-15, IL-2-pulsed T cells showed a significant increase in their stimulation. TNF-alpha up-regulated the IL-15-mediated proliferative response of bronchoalveolar lavage T lymphocytes. Following the block of the IL-2R beta- and gamma-chains with specific mAbs, the stimulatory activity of IL-15 was abolished. The evaluation of the IL-2R on sarcoid AMs demonstrated the constitutive expression of alpha- and gamma-chain mRNA and proteins. Taken together, these findings demonstrate that IL-15 triggers the growth of sarcoid T cells through the IL-2R beta/IL-2R-gamma complex and raise the possibility that AMs may deliver proliferative signals for the development of the T cell alveolitis. Modulation of IL-2R on AMs could represent a critical variable in regulating local inflammatory responses.
Agostini
C
C
Department of Clinical and Experimental Medicine, Padua University School of Medicine, Italy.
Trentin
L
L
Facco
M
M
Sancetta
R
R
Cerutti
A
A
Tassinari
C
C
Cimarosto
L
L
Adami
F
F
Cipriani
A
A
Zambello
R
R
Semenzato
G
G
D000328:Adult; D001483:Base Sequence; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D005260:Female; D006801:Humans; D019409:Interleukin-15 / Q000096:biosynthesis / Q000502:physiology*; D007376:Interleukin-2 / Q000096:biosynthesis / Q000502:physiology*; D008168:Lung / Q000276:immunology; D008213:Lymphocyte Activation; D016676:Macrophages, Alveolar / Q000276:immunology / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000502:physiology*; D017565:Sarcoidosis, Pulmonary / Q000150:complications* / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
C508024:IL15RA protein, human; D019409:Interleukin-15; D007376:Interleukin-2; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2