Values with a P-value < 0·05 were considered significant and are designated by an asterisk or diamond in the figures. Eosinophils are predominant in thyroids of IFN-γ−/− recipients of splenocytes from IFN-γ−/− donors 20 days after cell transfer, whereas thyroids of WT recipients of WT donor cells have extensive infiltration by neutrophils.6–8 IL-5 regulates eosinophil production,9 and

neutralization or gene knockout of IL-5 decreases eosinophil infiltration in models of allergy and other inflammatory diseases.9,24–28 To determine if the presence of eosinophils in IFN-γ−/− thyroids plays a role in determining the severity or outcome of G-EAT, anti-IL-5 was used to inhibit migration of eosinophils to thyroids of IFN-γ−/− mice. Very few eosinophils with typical pink granule staining were present in thyroids of WT mice (Fig. 1a), whereas many eosinophils were present in thyroids of IFN-γ−/− mice with G-EAT (Fig. 1b). Thyroids Cilomilast of IFN-γ−/− recipients given anti-IL-5 had many fewer eosinophils (Fig. 1c), indicating that the amount of anti-IL-5 was sufficient to inhibit infiltration of most eosinophils into thyroids of IFN-γ−/− mice. Thyroids of IFN-γ−/− mice given anti-IL-5 (Fig. 1f,i) had more neutrophils than thyroids of IFN-γ−/− mice

given IgG (Fig. 1e,h), but the extent of neutrophil infiltration was always much less than in thyroids of WT mice (Fig. 1d,g). Numbers of eosinophils (Fig. 1j, click here pink column) and neutrophils (Fig. 1j, brown column) in five or six randomly selected high-power fields for three individual mice per group (magnification: ×1000) were manually counted and results are summarized (Fig. 1j). Consistent with the extensive infiltration by neutrophils, thyroids of WT recipients

had extensive necrosis at day 20, whereas there was little necrosis in thyroids of IFN-γ−/− mice given anti-IL-5 (Table 1). Eosinophils and neutrophils had largely Fludarabine mw disappeared in all thyroids by day 40–50 (Table 1). These results indicate that administration of anti-IL-5 leads to less eosinophil infiltration and more neutrophil infiltration into thyroids of IFN-γ−/− mice. Protein expression of IL-5 at day 20 (Fig. 1k–m) was increased in thyroids of IFN-γ−/− mice given control IgG compared with that in thyroids of WT (Fig. 1l,k) or IFN-γ−/− mice given anti-IL-5 (Fig. 1l,m). As IL-5 neutralization correlates with reduced eosinophil infiltration and increased neutrophil infiltration into thyroids of IFN-γ−/− mice, this provides an excellent opportunity to address the role of eosinophils versus neutrophils in G-EAT resolution. Because anti-IL-5 markedly reduced eosinophil infiltration and resulted in increased neutrophil infiltration in thyroids of IFN-γ−/− mice (Fig. 1 and Table 1), we hypothesized that inhibiting infiltration of eosinophils into thyroids using anti-IL-5 might influence the severity and/or rate of resolution of G-EAT.