IgE-dependent sensitization increases responsiveness to LPS but does not modify development of endotoxin tolerance in mast cells.

ABSTRACT

OBJECTIVE: Effects of immunoglobulin E (IgE)-dependent sensitization on the response to bacterial lipopolysaccharide (LPS) were analyzed in mast cells. METHODS: Murine bone marrow-derived mast cells (BMMCs) were sensitized or not with IgE before stimulation with LPS. TLR4 and co-receptors expression was analyzed by flow cytometry and RT-PCR, TNF-α production by ELISA, IKK and IκB activation by western blot or immunoprecipitation. NFκB nuclear translocation was determined by EMSA. RESULTS: IgE-sensitized BMMCs secreted larger amounts of TNF-α than non-sensitized cells shortly after LPS challenge. No change in TLR4, CD14 or MD-2 expression was detected after the IgE-dependent sensitization process, whereas TLR4-dependent phosphorylation of IKK and IκB was augmented. IgE-dependent sensitization increased basal NFκB activity. Endotoxin tolerance was not affected by the IgE-dependent sensitization process. CONCLUSIONS: IgE-induced sensitization primes mast cells for higher response to LPS through pre-activation of NFκB transcription factor. IgE-dependent sensitization does not modify events leading to endotoxin tolerance.