Keratinocyte-specific deletion of STAT3 promotes elevated serum IgE in response to Staphylococcus aureus exposure: relevance to hyper-IgE syndrome

Autosomal dominant hyper-IgE syndrome is caused by STAT3 loss-of-function mutations, which results in a constellation of clinical features, including highly elevated serum IgE levels, a severe eczema-like skin eruption, and an increased susceptibility to Candida albicans and Staphylococcus aureus skin infections. However, the mechanism by which these individuals have elevated IgE levels is not well understood. To evaluate the role of defective STAT3 signaling in contributing to IgE production, we used a mouse model of atopic dermatitis-like skin inflammation induced by epicutaneous exposure to S. aureus in cre/lox mice with cell specific deletion of STAT3. Unexpectedly, STAT3 deletion in keratinocytes (K5-cre ERT2 × STAT3 fl/fl mice) but not in T cells (CD4-cre ERT2 × STAT3 fl/fl mice) resulted in a substantial elevation of serum IgE levels. The increase in serum IgE involved concomitant increase in IgG and IgA levels that were also significantly higher in the keratinocyte-specific STAT3-deficient mice compared with wildtype mice. CD4 + T cells were required for the IgE production, since CD4 + T cell depletion resulted in significantly reduced level of serum IgE in the K5-cre ERT2 × STAT3 fl/fl mice. Taken together, these results indicate that keratinocytes can modulate serum antibody levels, especially in the absence of STAT3 signaling. These results provide an explanation of the increased serum IgE levels in autosomal dominant hyper-IgE syndrome and more broadly into the mechanisms that promote antibody production in response to epicutaneous exposure to microbes and inflammation.