Differential roles for the IL-9/IL-9 receptor alpha-chain pathway in systemic and oral antigen-induced anaphylaxis

Abstract

Background: The cytokine IL-9 has been implicated in allergic reactions, including food allergy, but its contribution to parenteral versus oral antigen-induced anaphylaxis remains unclear.

Objectives: We sought to delineate the contribution of the IL-9/IL-9 receptor alpha-chain (IL-9R) pathway to parenteral and oral antigen-induced anaphylaxis.

Methods: Wild-type, IL-9-deficient (Il9(-/-)), and IL-9R-deficient (Il9R(-/-)) mice were subjected to passive and active parenteral and oral antigen (ovalbumin [OVA])-induced anaphylaxis. Severity of systemic anaphylaxis was gauged by decreased body temperature; intestinal anaphylaxis was assessed based on secretory diarrhea, intestinal mastocytosis, and serum murine mast cell protease 1 level. Specific immunoglobulin isotypes or immunoglobulin receptor-blocking antibodies were administered before challenge to define the role of the IgE and IgG pathways.

Results: Repeated oral antigen challenge of OVA-sensitized wild-type mice induced anaphylaxis with both systemic and intestinal involvement; both were IgE dependent and attenuated in Il9(-/-) and Il9R(-/-) mice. In contrast, parenteral OVA challenge of OVA-sensitized wild-type mice induced systemic anaphylaxis, which was independent of the IL-9/IL-9R pathway. Strikingly, the IL-9/IL-9R pathway had no role in either the IgG or IgE component of parenteral antigen-induced or anti-IgE and anti-FcgammaRII/III mAb-induced systemic anaphylaxis.

Conclusions: Parenteral antigen-induced murine systemic anaphylaxis is mediated by both IgG- and IgE-dependent pathways, and both can occur independently of IL-9/IL-9R signaling. In contrast, oral antigen-induced intestinal and systemic anaphylaxis is strictly IgE mediated and requires IL-9/IL-9R signaling. These studies indicate differential involvement of the IL-9/IL-9R pathway in systemic and oral antigen-induced anaphylaxis.

FIG 1

Critical role for the IL-9/IL-9R pathway in anaphylaxis induced by oral antigen challenge. A, Diarrhea occurrence in vehicle (Veh)– or OVA-sensitized intragastric (i.g.) OVA-challenged WT, Il9R^2/2, and Il9^2/2 mice. A and B, Serum mouse mcpt-1 levels (Fig 1, B) and temperature change (Fig 1, C) from 0 to 60 minutes after the sixth intragastric vehicle or OVA challenge in OVA-sensitized WT, Il9R^2/2, and Il9^2/2 mice. Data in Fig 1, A, are represented as a percentage of diarrhea occurrence after a number of OVA challenges. The fraction indicates the number of mice with diarrhea out of the total number of mice in that group. Data in Fig 1, B and C, are representative after the sixth intragastric vehicle or OVA challenge in OVA-sensitized WT, Il9R^2/2, and Il9^2/2 mice. Fig 1, B, Four to 8 mice per group from n = 3 experiments. *P < .05. Fig 1, C, Individual symbols represent 1 mouse. *P < .001.

FIG 2

No role for the IL-9/IL-9R pathway in anti-IgE–mediated passive systemic anaphylaxis. A, Rectal temperature in control immunoglobulin (Ig)– and anti-IgE–treated WT, Il9^2/2, and Il9R^2/2 mice. Total IgE levels (B) and mast cells per high-power field (HPF) in the tongue (C), ear skin (D), and small bowel (E) in control Ig– and anti-IgE–treated WT, Il9^2/2 and Il9R^2/2 mice. F, Serum mcpt-1 concentrations in control Ig and anti-IgE mAb–challenged WT, Il9^2/2, and Il9R^2/2 mice. Fig 2, A and F, n = 3 to 7 mice per group. *P < .05 compared with WT control Ig–treated mice. Fig 2, C through E, n = 4 mice per group. Fig 2, B, n = 4–6 mice per group from duplicate experiments. n.s., Not significant. OD; optical density.

FIG 3

No role for the IL-9/IL-9R pathway in anti-FcgRII/III–mediated passive systemic anaphylaxis. A and B, Total IgG1 and IgG2a levels in WT, Il9^2/2, and Il9R^2/2 mice. C, Rectal temperature response of WT, Il9^2/2, and Il9R^2/2 mice to intravenous injection of anti-FcgRII/III mAb or control immunoglobulin (control Ig; J1.2). Fig 3, A and B, n = 4 mice per group from duplicate experiments. Fig 3, C, n = 5–11 mice per group. *P < .05 compared with WT control mice.

FIG 4

No role for the IL-9/IL-9R pathway in parenteral antigen–induced anaphylaxis. Rectal temperatures (A) and serum mcpt-1 concentrations (B) in OVA-sensitized WT, Il9^2/2 , and Il9R^2/2 mice injected intravenously with OVA or vehicle (Veh). Fig 4, A and B, n = 4 mice per group from duplicate experiments. *P < .05 compared with WT control.

FIG 5

No role for the IL-9/IL-9R pathway in IgE- or IgG-mediated parenteral OVA-induced systemic anaphylaxis. Rectal maximum temperature changes and serum mcpt-1 concentrations in OVA-sensitized mice desensitized with immunoglobulin control (control Ig; GL117 1 J1.2), anti-IgE mAb, or anti-FcgRII/III mAb and challenged intravenously with OVA are shown. A, WT mice. B, Il9^2/2 mice. C, Il9R^2/2 mice. Data represent means 6 SEMs; n = 3–6 mice per group from duplicate experiments. *P < .05 compared with control Ig.