significantly more type 2 cytokines relative to WT animals. In addition, OVA-sensitized SOCS2/ mice had significantly increased airway resistance, specific IgE, and airway inflamma- tion after OVA challenge. Our data suggest a novel role for SOCS2 in controlling CD4+ lineage commitment and type 2 allergic responses. RESULTS SOCS2 deficiency is associated with enhanced IL-4, IL-5, and IL-13 secretion and Th2 differentiation both in vitro and in vivo SOCS2/ mice present with gigantism but with no reported obvious immune defect (Metcalf et al., 2000). Phenotyping of 1524 Figure 1. Increased secretion of Th2- associated cytokines in SOCS2/ mice in vitro and in vivo. (A) CD4+CD25 sple- nocytes purified from WT and SOCS2/ mice were cultured for 3 or 5 d with 2 µg/ml of plate-bound anti-CD3, 1 µg/ml of plate-bound anti-CD28, and 5 U/ml IL-2 in triplicate and cytokine production was evaluated by ELISA. Data are representative of at least three independent experiments. (B) Naive CD4+CD25CD44 splenocytes were cultured for 7 d under Th2 polariza- tion conditions. Frequency of CD4+IL-4+ cells (Th2 cells) was evaluated at days 4 and 7 by intracellular staining. Data are representative of three independent experi- ments performed in triplicate. (C) SOCS2/ and WT mice (n = 5 per group) were i.p. injected with 10,000 S. mansoni eggs or PBS. 10 d later, splenocytes were restimu- lated with anti-CD3 and anti-CD28 or SEA and cytokine production was measured by ELISA. (D and E) The footpads of WT and SOCS2/ mice (n = 5 per group; D) or RAG-1/ mice reconstituted with CD4+ T cells sorted from WT (n = 4 per reconsti- tuted group; E) or SOCS2/ mice (n = 7 per reconstituted group; E) were injected with 5,000 S. mansoni eggs or PBS. 10 d later, the amount of Th2 cells in popliteal LNs was determinate by IL-4 intracellular staining (D) or T1/ST2 (IL-33 receptor) staining (E). Data are representative of at least three experiments and presented as the mean and SEM of each group. *, P < 0.05; **, P < 0.01; ***, P < 0.001. thymus, spleen, and LN of SOCS2/ and WT mice showed similar fre- quency and numbers of CD4+, CD8+, double-positive, and double-negative T cells (Fig. S1, A and B), suggesting that T cell development was nor- mal. However, as other SOCS fam- ily members have important roles in determining the cytokine responsiveness of different Th subsets (Palmer and Restifo, 2009), we examined the cyto- kine profile of CD4+ T cells from SOCS2/ mice after TCR stimulation in vitro. IL-2 and IFN- secretion were similar in CD4+ T cells from SOCS2/ and WT mice but, surprisingly, IL-4, IL-5, IL-10, and IL-13 levels were mark- edly higher in the absence of SOCS2 (Fig. 1 A). Moreover mRNA levels of these cytokines were also enhanced when examined by real-time PCR (Fig. S1 C). Importantly the level of GATA-3 mRNA was significantly higher in SOCS2/ CD4+ T cells (Fig. S1 C), suggesting spontaneous enhance- ment of Th2 polarization. To explore this more closely, we sorted naive CD4+CD25CD44low T cells and drove de SOCS2 regulates Th2 responses | Knosp et al.