Induction of tolerance after establishment of peanut allergy by the food allergy herbal formula‐2 is associated with up‐regulation of interferon‐γ

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Abstract
Background Peanut (PN)‐anaphylaxis is potentially life threatening. We previously reported that a Chinese herbal medicine preparation, food allergy herbal formula‐2 (FAHF‐2), prevented peanut allergy (PNA) in mice when administered during sensitization. Objective To investigate whether FAHF‐2 also can prevent anaphylactic reactions when administered to mice with established PNA and, if so, whether protection would persist after cessation of therapy. Methods C3H/HeJ mice sensitized and boosted over 8 weeks with a standard protocol known to establish PN hypersensitivity received seven weeks of FAHF‐2 treatment or water as a sham treatment. Mice were subsequently challenged with PN at week 14 (1‐day post‐therapy) and week 18 (4‐week post‐therapy) to evaluate the efficacy and persistence of FAHF‐2 treatment by assessing anaphylactic scores, core body temperatures and plasma histamine levels. Serum PN‐specific antibody levels and cytokine profiles from splenocytes and mesenteric lymph node (MLN) cells were also determined. Results All sham‐treated mice challenged at weeks 14 and 18 showed anaphylactic symptoms. In contrast, FAHF‐2‐treated mice showed no sign of anaphylactic reactions. PN‐specific IgE levels in FAHF‐2‐treated mice also were reduced whereas IgG2a levels were increased. Furthermore, MLN cells from FAHF‐2‐treated mice produced markedly less IL‐4 and IL‐5, but more IFN‐γ, and contained increased numbers of IFN‐γ‐producing CD8+ cells as compared with sham‐treated mice. Conclusion FAHF‐2 treatment established PN tolerance in this model, which persisted for at least 4‐week post‐treatment. This result was associated with modulation of intestinal T helper type 1 cell (Th1) and Th2 cytokine production, and with increased numbers of mesenteric IFN‐γ‐producing CD8+ cells.

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