Interleukin-15 Triggers the Proliferation and Cytotoxicity of Granular Lymphocytes in Patients With Lymphoproliferative Disease of Granular Lymphocytes

• DOI: 10.1182/blood.v89.1.201
• Publication Date: 2019-10-14T12:52:52Z
• Authors: R. Zambello; M. Facco; L. Trentin; R. Sancetta; C. Tassinari; A. Perin; A. Milani; G. Pizzolo; F. Rodeghiero; C. Agostini; R. Meazza; S. Ferrini; G. Semenzato
• Keywords: Adult; Cytotoxicity, Immunologic; Interleukin-15; Male; 0301 basic medicine; 0303 health sciences; Antibodies, Monoclonal; Gene Expression; Middle Aged; Lymphocyte Activation; Antigens, Differentiation; Polymerase Chain Reaction; Lymphocyte Subsets; Lymphoproliferative Disorders; Immunophenotyping; 3. Good health; 03 medical and health sciences; Humans; Interleukin-2; Female; RNA, Messenger; Cell Division; Cells, Cultured; Aged

AbstractThe recently cloned cytokine interleukin-15 (IL-15) shares several functional activities with IL-2 in different cell systems. Although IL-15 does not show sequence homology with IL-2, it uses components of the IL-2 receptor (IL-2R) for binding and signal transduction, namely, p75 (β) and the p64 (γ) chains of IL-2R. To evaluate whether IL-15 is involved in the activation of granular lymphocytes (GL) in patients with lymphoproliferative disease of granular lymphocytes (LDGL), we evaluated the ability of IL-15 to stimulate GL proliferation, cytotoxic function, and the role of IL-2R β and γ molecules on relevant cells. Our results show that IL-15 stimulates cell proliferation and cytotoxic activity of GL in LDGL patients. Reverse-transcriptase polymerase chain reaction (RT-PCR) and phenotypic analyses using the anti–IL-2R γ-chain–specific TUGh4 monoclonal antibody (MoAb) indicate that both CD3+ and CD3− GL express the p64 IL-2R, a result previously unknown. IL-15 activity was inhibited by antibodies against p75 and p64 IL-2R chains, while no inhibitory effects are detectable with anti-p55 IL-2R antibody. The association of anti-p75 and anti-p64 IL-2R MoAbs resulted in a nearly complete (95%) inhibition of IL-15–induced GL proliferation. Using RT-PCR analysis, we demonstrated that highly purified CD3+ and CD3− GL did not express mRNA for IL-15 or IL-2. By contrast, a clear-cut IL-15 mRNA signal was detected by RT-PCR in patients' peripheral blood mononuclear cells, with monocytes likely accounting for the source of IL-15 in LDGL patients. However, even in concentrated supernatants from enriched monocyte populations, we could not demonstrate the presence of IL-15 protein. Using anti–IL-15 specific MoAbs, a membrane-bound form of this cytokine was demonstrated both on CD3+ and CD3− LDGL cells. By RT-PCR analysis, purified GL from these patients were found to express the message for IL-15 receptor α chain. Taken together, these results indicate that both CD3+ and CD3− GL are stimulated by IL-15 and that this cytokine mediates its activity through the β and γ chains of the IL-2R, providing further suggestions for the interpretation of the mechanisms that lead to cell expansion in patients with LDGL.