Background: The molecular determinants of the severity and persistence of allergic asthma remain poorly understood. Suppressor of cytokine signalling 1 (SOCS1) is a negative regulator of IL-4-dependent pathways in vitro and might therefore control T-helper type 2 (Th2) immunity associated traits, such as IgE levels, mucin production, IL-5 and IL-13 induction, and eosinophilic mucosal inflammation, which are implicated in allergic asthma.
Objective: To investigate the role of SOCS1 in regulating Th2-associated disease traits in a murine sub-chronic aeroallergen-driven asthma model.
Methods: Following sensitization and challenge with ovalbumin (OVA), bronchoalveolar lavage and serum were collected from mice lacking the Socs1 gene on an IFN-gamma null background (Socs1(-/-)Ifngamma(-/-)). The composition of infiltrating cells in the lung, serum IgE and IgG1 levels and cytokine levels were analysed.
Results: Serum IgE levels and infiltrating eosinophils were considerably increased in the lungs of OVA-treated Socs1(-/-)Ifngamma(-/-) mice compared with Ifngamma(-/-) and C57BL/6 controls. Expression of the Th2 cytokines, IL-4, IL-5 and IL-13 was increased in CD4+ cells and lung tissue from OVA-treated Socs1(-/-)Ifngamma(-/-) mice. IgE, IL-5 levels and infiltrating eosinophils were also elevated in saline-treated Socs1(-/-)Ifngamma(-/-) mice, suggesting that in the absence of SOCS1, mice are already biased towards a Th2 response. It is at present unclear whether the elevated cytokine levels are sufficient to result in the exacerbated Th2 response to OVA challenge or whether enhanced intra-cellular signalling also contributes. Surprisingly, of the various IL-4/IL-13 responsive genes tested, only Arginase I appeared to be modestly up-regulated in the lungs of OVA-treated Socs1(-/-)Ifngamma(-/-) mice, suggesting that regulation by SOCS1 occurs primarily in haematopoietic cells and not in the airway epithelium.
Conclusions: Together these results indicate that SOCS1 is an important regulator of the Th2 response.