FcεRI-mediated mast cell response is modulated by TLR2 and TLR4 ligation

It is well documented that mast cells express both Fc epsilon RI and Toll-like receptors (TLRs). It is also suggested that subsequent/simultaneous mast cell activation via TLR and Fc epsilon RI may affect these cells activity. In the present study we examined the influence of lipoarabinomannan (LAM), that is TLR2 ligand, and lipopolysaccharide (LPS), that is TLR4 agonist, on mast cell degranulation and preformed mediator release and cysteinyl leukotriene (cysLT) generation mediated by Fc epsilon RI aggregation. Our experiments were performed on native rat peritoneal mast cells and on peritoneal mast cells pre-coated in vitro with IgE. We found that neither LAM- nor LPS-priming modified degranulation of native mast cells. Under the same experimental conditions LAM-induced TLR2 ligation caused statistically significant (p < 0.01) decrease in Fc epsilon RI-mediated histamine release from IgE-coated mast cells. Moreover, we noticed that simultaneous stimulation via TLR4 or TLR2 and Fc epsilon RI resulted in synergistic amplification of cysLT generation from IgE-coated mast cells and, to a lesser extent, from native mast cells. These observations might be a clue to understanding the mechanistic basis of allergic disease exacerbation upon coexisting infections.