HRF Transgenic Mice Phenotype Figure 9. Serum and BAL IgE Levels. Panel A illustrates the average total serum IgE +/2 SEM for each group of mice. Panel B is the average IgE levels detected in BAL supernatants from the same mice. IgE levels were measured by ELISA. N = 629 mice per group (backcrosses 3–6). doi:10.1371/journal.pone.0011077.g009 4 from human basophils [8]. In fact, IL-4 as well as IL-13 production and histamine release was observed in response to HRF from a subset of allergic donors basophils [9]. In addition, HRF primed all donors’ basophils for IgE dependent mediator release following antigen or anti-IgE stimulation. Not surprisingly, in human work done in vitro, HRF has also been shown to cause chemotaxis of eosinophils and secretion of IL-8 from allergic donors [12]. In the present study, the allergen sensitized and challenged mice also had increased numbers of infiltrating eosinophils in their lungs (Figure 8). Although our previous work in human cells showed HRF caused IL-13 secretion, we did not see any changes in mRNA for IL-13 in the lung of transgenic HRF mice, in the presence or absence of OVA sensitization and challenge. IL-13 has been linked to airway hyper responsiveness and mucous production in the same mouse model of allergy [23]. Therefore, given the lack of IL-13 expression in our transgenic mice it is not surprising that we do not see increased AHR or mucous production. HRF has been shown to be present in the BAL of asthmatic patients [18] as well as in the nasal lavage [1] and skin blister fluids of patients with late phase allergic inflammation [33]. In the present study, we could detect HRF in the BAL of the mice (see Figure 6). The exact cell type that HRF activates in this model is not known. However, given the fact that we see increased IL-4 levels and eosinopils recruited into the BAL, the mouse basophil is a likely candidate. Mouse basophils have been shown to be the cells responsible for secretion of IL-4 [34,35]. In fact, human and mice basophils have been demonstrated to have more IL-4 per cell than T cells and to be responsible for IL-4 secretion in allergic reactions [36,37]. Future experiments are designed to test the Figure 10. Cytokine and Chemokine Expression Levels. Panel A depicts relative mRNA levels compared to the housekeeping gene, beta actin, using primers specific to each cytokine or chemokine noted. Equal amounts of RNA were used for this relative quantitation. Panel B shows protein levels in BAL supernatants for IL-4 measured by ELISA. N = 629 mice per group. Groups of mice are the same as described in Figure Legend 4 (backcrosses 3–6). doi:10.1371/journal.pone.0011077.g010 PLoS ONE | www.plosone.org 10 June 2010 | Volume 5 | Issue 6 | e11077