Sensitization increases esterase-positive macrophage number in appendix from an animal model of food allergy.

BACKGROUND Macrophages are mononuclear cells with phagocytic and antigen presenting properties. The role of macrophages in IgE-dependent allergic reactions and oral tolerance remains unclear. In previous works we demonstrated that ovalbumin (OVA)-sensitized rabbits present histopathological modifications of the mucosa in different regions of the digestive tract. The present study analyzes macrophage distribution and quantitative modifications in the cecal appendix of OVA-sensitized animals. METHODS Adult new Zealand rabbits were divided into two groups: G1 (non-sensitized normal controls) and G2 (rabbits sensitized to OVA twice by subcutaneous route, with aluminum hydroxide as adjuvant). The alpha-naphthyl esterase technique was used for macrophage detection. RESULTS Specific anti-OVA IgE was detected in sensitized animals by the PCA (passive cutaneous anaphylaxis) method. In 5 regions of the cecal appendix we observed a significant increase in the number of macrophages in sensitized animals (G2) versus the control group (G1). The observed sensitization-mediated increase in cells is probably related to enhanced recruitment of monocytes from peripheral blood towards the appendix. This process could be induced by chemical mediators, and demonstrates macrophage participation in local immune response during sensitization phenomena.