Background
Severe IgE-mediated, food-induced anaphylactic reactions are characterized by pulmonary venous vasodilatation and fluid extravasation, which is thought to lead to the life-threatening anaphylactic phenotype. The underlying immunological and cellular processes involved in driving fluid extravasation and the severe anaphylactic phenotype are not fully elucidated.
Objective
To define the interaction and requirement of IL-4 and vascular endothelial (VE) IL-4Rα chain signaling in histamine-ABL1–mediated VE dysfunction and fluid extravasation in the severity of IgE-mediated anaphylactic reactions in mice.
Methods
Mice deficient in VE IL-4Rα and models of passive and active oral antigen– and IgE-induced anaphylaxis were employed to define the requirements of VE IL-4Rα and ABL1 pathway in severe anaphylactic reactions. Human VE cell line (EA.hy926 cells) and pharmacologic (imatinib) and genetic approaches (shRNA knockdown of IL4RA and ABL1) were used to define the requirement of this pathway in VE barrier dysfunction.
Results
IL-4 exacerbation of histamine-induced hypovolemic shock in mice was dependent on VE expression of the IL-4Rα. IL-4 and histamine induced ABL1 activation in human VE cells and VE barrier dysfunction was ABL1 dependent. Development of severe IgE-mediated hypovolemia and shock required VE-restricted ABL1 expression. Treatment of mice with a history of food-induced anaphylaxis with the ABL kinase inhibitor imatinib protected the mice from developing severe IgE-mediated anaphylaxis.
Conclusion
IL-4 amplifies IgE- and histamine-induced VE dysfunction, fluid extravasation, and severity of anaphylaxis via a VE IL-4Rα-ABL1–dependent mechanism. These studies implicate an important contribution by the VE compartment in the severity of anaphylaxis and identify a new pathway for therapeutic intervention of IgE-mediated reactions.
SLC9A3 plays a functional role in DIS formation, and pharmacologic interventions targeting SLC9A3 function may suppress the histopathologic manifestations in patients with EoE.
Background
Clinical and experimental analyses have identified a central role for IgE/FcεRI/mast cells in promoting IgE-mediated anaphylaxis. Recent data from human studies suggest that bacterial infections can alter susceptibility to anaphylaxis.
Objective
We examined the effect of LPS exposure on the induction of IgE-mast cell-(MC) mediated reactions in mice.
Methods
C57BL/6 WT, TLR-4−/− and IL10−/− mice were exposed to LPS and serum cytokines (TNF and IL-10) were measured. Mice were subsequently treated with anti-IgE and the symptoms of passive IgE-mediated anaphylaxis, MC activation, Ca2+-mobilization and expression of FcεRI on peritoneal MCs were quantitated.
Results
We show that LPS exposure of C57BL/6 WT mice constrains IgE-MC mediated reactions. LPS-induced suppression of IgE-MC mediated responses was TLR-4-dependent and associated with increased systemic IL-10 levels, decreased surface expression of FcεRI on MCs and loss of sensitivity to IgE activation. Notably, LPS-induced desensitization of MCs was short-term with MC sensitivity to IgE reconstituted within 48 hours which was associated with recapitulation of FcεRI expression on the MCs. Mechanistic analyses revealed a requirement for IL-10 in LPS-mediated decrease in MC FcεRI surface expression.
Conclusions & Clinical Relevance
Collectively, these studies suggest that LPS-induced IL-10 promotes the down regulation of MC surface FcεRI expression and leads to desensitization of mice to IgE-mediated reactions. These studies indicate that targeting of the LPS-TLR-4-IL-10-pathway maybe used as a therapeutic approach to prevent adverse IgE-mediated reactions.
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