IL9 and mastocytosis: Conversely, in the absence of IL-9 or IL-9R, repeated oral challenge with a food allergen (ovalbumin, OVA) makes mice produce OVA-specific IgE and IgG, but lack other parameters associated with a food allergic response such as hypothermia, intestinal mastocytosis, and increased serum levels of mast cell protease-1 (MCPT-1) (30).