CD4⁺ T cell-derived IFN-γ and LIGHT synergistically upregulate chemokine production from airway smooth muscle cells

Airway smooth muscle (ASM) remodeling in asthmatic airways may contribute to persistent airflow limitation and airway hyperresponsiveness. CD4⁺ T cells infiltrate the ASM layer where they may induce a proliferative and secretory ASM cell phenotype. We studied the interaction between activated CD4⁺ T cells and ASM cells in co-culture in vitro and investigated the effects of CD4⁺ T cells on chemokine production by ASM cells. CD4⁺ T cells induced marked upregulation of C-X-C motif chemokine ligands (CXCL) 9, 10, and 11 in ASM cells. Blockade of the IFN-γ receptor on ASM cells prevented this upregulation. Furthermore, T cell-derived IFN-γ and LIGHT (lymphotoxin, exhibits inducible expression and competes with HSV glycoprotein D for binding to herpesvirus entry mediator, a receptor expressed on T lymphocytes) synergize in a dose-dependent manner to coordinately enhance CXCL9, 10, and 11 expression. The synergistic property of LIGHT was mediated exclusively through the lymphotoxin-β receptor (LTBR), but not herpes virus entry mediator (HVEM). Disruption of LTBR signaling in ASM cells reduced CXCL9, 10, and 11 production and ASM cell-mediated CD4⁺ T cell chemotaxis. We conclude that the LIGHT-LTBR signaling axis acts together with IFN-γ to regulate chemokines that mediate lymphocyte infiltration in asthmatics.