FcϵRI and TLR2-dependent cytokine generation by human mast cells utilize both convergent and divergent signaling pathways

• Published in: Journal of allergy and clinical immunology Vol. 113; no. 2; p. S101
• Main Authors: Bagga, S., Lora, J.M., Villeval, J., Coyle, A.J., Feng, C., Boyce, J.A.
• Format: Journal Article
• Language: English
• Published: Mosby, Inc 2004
• ISSN: 0091-6749; 1097-6825
• DOI: 10.1016/j.jaci.2003.12.353

Mast cells (MCs), effector cells of allergic reactions through FcϵRI, also initiate innate immune responses through pattern recognition receptors such as Toll-like receptors (TLRs). Stimulation of human MCs (hMCs) through either FcϵRI or TLR2 initiates cytokine gene expression; whether this process involves separate or distinct downstream signaling in hMCs is not known. Cord blood derived hMCs generated IL-5, IL-6, IL-13, TNF-α, MIP-1β, I-309, Rantes and MCP1 in response to both FcϵRI cross-link with α-IgE (1 μg/ml) and TLR2-dependent activation with staph peptidoglycan (PGN, 10 μg/ml). IL-4 priming substantially enhanced cytokine generation (MIP-1β, IL-5 and TNF-α) to both activating ligands. TNF-α generation through FcϵRI was markedly sensitive to the calcineurin inhibitor cyclosporine (CsA), (5 μg/ml) (93 ± 2 %inhibition) and UO126 (5 μg/ml), an inhibitor of MEK/ERK signaling (88 ± 5% inhibition) whereas PGN-dependent TNF-α production was less sensitive to these inhibitors (20 ± 15% and 50 ± 11% respectively). Both FcϵRI and TLR2-dependent stimulation elicited NF-κB-dependent transcription, as evidenced by blockade of TNF-α secretion by the IKK2 inhibitor PS1145 (72 ± 18 and 59 ± 11% inhibition respectively), which also attenuated nuclear translocation of p65 in the IgE and PGN samples. P38 inhibitor SB203580 (10 μg/ml) also inhibited cytokine generation through both the receptors. We conclude that hMCs uses both convergent and divergent pathways to generate cytokines in response to stimuli pertinent to allergy and to innate host protection, respectively. Furthermore, IL-4 amplifies cytokine generation through both receptor systems, suggesting an effect at the level of a common post-receptor signaling event.