Interleukin-7 promotes lung-resident CD14⁺ monocytes activity in patients with lung squamous carcinoma

Interleukin (IL)-7 enhances cytokines secretion by CD14⁺ monocytes, and induces recruitment of monocytes to endothelium. As an important regulator to different types of immune cells, the role of IL-7 in modulation of CD14⁺ monocytes is still not fully elucidated. Thus, the aim of current study was to investigate the immunoregulatory activity of IL-7 to peripheral and lung-resident CD14⁺ monocytes in lung squamous carcinoma patients. Thirty-seven lung squamous carcinoma patients and eighteen healthy individuals were enrolled. CD14⁺ monocytes and CD4⁺ T cells were purified from both peripheral bloods and bronchoalveolar lavage fluids (BALF). IL-7 expression in plasma and BALF was measured by ELISA, and CD127 expression in peripheral and lung-resident CD14⁺ monocytes was investigated by real-time PCR and flow cytometry, respectively. Cellular proliferation, cytokine production, and molecules in IL-7 signaling pathway was assessed in CD14⁺ monocytes in response to IL-7 stimulation. IL-7-induced CD14⁺ monocytes activity to CD4⁺ T cells was also assessed in direct and indirect contact co-culture system. There were no remarkable differences of plasma IL-7 concentration or CD127 level between healthy individuals and lung squamous carcinoma patients. However, IL-7 expression was significantly reduced in BALF from tumor site in squamous carcinoma patients, especially in stage III and IV. IL-7 stimulation not only promoted proliferation, cytokines secretion, and STAT-5 phosphorylation in lung-resident CD14⁺ monocytes, but also enhanced CD14⁺ monocytes-induced Th1 and T follicular helper cells activation, which presented as elevated interferon-γ and IL-21 secretion by CD4⁺ T cells. This process required direct cell-to-cell contact, and was dependent on IL-6 secretion. The current data revealed a potential immunopromotive property of IL-7 to lung-resident CD14⁺ monocytes in lung squamous carcinoma.