Effector Pathways in Peanut-Induced Anaphylaxis Figure 5. Basophils and monocytes/macrophages in PE-induced systemic anaphylaxis. C3H/HeOuJ (C3H) and C57BL/6 mice were exposed to PBS+CT (cont) or PE+CT (PE) during a 4 week period, as described in material and methods. Prior to oral sensitization (sens) or i.p. challenge (chall) indicated groups received BA103, a basophil depleting antibody. A, Serum levels of PE-specific IgE, IgG1 and IgG2a at day 36. B, Temperature after i.p. challenge. C, Serum MMCP-I levels after challenge. Prior to challenge, in indicated groups, monocytes/macrophages were depleted using clodronate liposomes. D, Temperature after i.p. challenge. Data are represented as mean 6 SEM of 6–8 mice. *: p,0.05 compared to control. # p,0.05 compared to C3H PE group or to C57BL/6 PE group. doi:10.1371/journal.pone.0028917.g005 In summary, in this study we describe marked differences in parameters and manifestations of food allergy in different mouse strains. In addition, we show a role of components of the alternative pathway of anaphylaxis in a food allergy model. However, clear differences exist between mouse strains in participation of this pathway. In conclusion, clinical manifestations of food allergy and anaphylaxis are not simply and directly linked to the classical components of the allergic cascade. This might explain the pleiomorphic manifestations of the clinical phenomena in the human situation. In addition, these findings may have important implications for diagnosis of and finding new targets for treatment of food allergy and food-induced anaphylaxis. Methods Mice Five-week-old specific pathogen-free female C3H/HeOuJ, C57BL/6J, and BALB/cByJ mice were purchased from Charles River (France) and housed under specific pathogen-free conditions within the animal care facility at the Utrecht University. Mast cell- deficient C57BL/6W-sh/W-sh or FcRc2/2 mice, both on a C57BL/6 background, were bred and maintained at the animal care facility at the Utrecht University. Experiments in this study were approved by the Animal Experiments Committee of the Utrecht University (ID #2011.III.03.031). Peanut oral sensitization and challenge Peanuts were kindly provided by Intersnack BV (the Nether- lands) and peanut extract (PE) was prepared as previously described [15]. Cholera toxin (CT) was obtained from List Biological Laboratories, Inc. (CA, USA) To elicit oral sensitization to PE, mice were intragastrically (i.g.) dosed with 6 mg PE plus 15 mg CT per mouse for three consecutive days, and this was repeated every week for four weeks (exposure on days 0, 1, 2, 7, 14, 21 and 28). Control groups received PBS plus 15 mg CT. Thereafter, mice received an i.g. challenge of 15 mg PE on day 35 and were sacrificed one day later. Measurement of ear swelling Acute ear swelling in PE-sensitized mice was determined after intradermal challenge with 10 mg PE in the right ear pinnae. As a Figure 6. Mast cells in PE-induced systemic anaphylaxis. C57BL/6 WT and mast cell deficient C57BL/6W-sh/W-sh mice were exposed to PBS+CT (cont) or PE+CT (PE) during a 4 week period, as described in material and methods. A, Serum levels of PE-specific IgE, IgG1 and IgG2a at day 36. B, Temperature after i.p. challenge. Data are represented as mean 6 SEM of 6 mice. *: p,0.05 compared to control. doi:10.1371/journal.pone.0028917.g006 PLoS ONE | www.plosone.org 9 December 2011 | Volume 6 | Issue 12 | e28917