Hyper-immunoglobulin E syndrome (Job's syndrome) is an immunodeficiency characterized by highly elevated serum IgE and recurrent skin and lung abscesses from inappropriately mild immune responses to staphylococcal infection. Both sporadic and autosomal dominant Job's syndrome patients are caused by mutations in the gene coding for STAT3, which results in impaired cytokine signaling in immune cells. The STAT3 signaling deficiency is responsible for many lymphocyte abnormalities observed in Job's syndrome patients such as impaired TH17 differentiation, defective development and maintenance of central memory T cells and reduced memory B cells. However, the effect of STAT3 deficiency on NK cell development and function in Job's syndrome patients has not been studied yet. Previous work performed in our lab employing STAT3 activating cytokines and STAT3 inhibitors showed that STAT3 activation plays a role in NK cell proliferation, survival, cytolytic activity, and regulation of expression of the activating receptor NKG2D. This finding prompted us to test whether aberrant STAT3 activation affects NK cell proliferation, survival and cytolytic activity, in NK cells of Job's syndrome patients.
To assess proliferation, cytolytic activity and receptor expression on NK cells from Job's syndrome patients with dominant negative STAT3 mutations.
NK cell proliferation was induced by stimulating peripheral blood mononuclear cells (PBMCs) with K562-based artificial antigen presenting cells genetically modified to express membrane bound cytokines. IL10 and IL21 were applied to induce STAT3 activation. Receptor expression was measured by flow-cytometry. NK cytolytic activity was evaluated by Calcein release assay. NK cells from normal, healthy donors were used as control. Statistical comparison was performed by paired Student's t test using GraphPad Prism.
Flow-cytometric analysis of PBMCs showed significantly lower percentage of NK cells, identified as CD3− CD56+, in Job's syndrome patients compared to normal donors. The expansion in response to membrane bound IL21 stimulation was found to be impaired in NK cells obtained from Job's syndrome patients compared to those from normal donors. Expanded NK cells from Job's syndrome patients had lower percentage of mature, CD56+CD16+NK cells compared to those from normal donors. We also found significantly reduced cytolytic activity in NK cells from Job's syndrome patients. STAT3 activating cytokines IL10 and IL21 were also found to be impaired in their ability to induce NKG2D expression on NK cells obtained from Job's syndrome patients.
Our finding of deficient NK cell number and cytolytic activity in Job's syndrome patients is the first to show an NK cell defect in this immunodeficiency. Lower percentage of NK cells in the peripheral blood and impaired ex vivo expansion of Job's syndrome patient's NK cells suggest deficient development and/or deficient proliferation and survival of NK cells in Job's syndrome patients with dominant negative STAT3 mutations. Along with recurrent bacterial infections, Job's syndrome patients are also more prone to viral infections and lymphoma. Given the role of NK cells in the immune surveillance of virally infected and tumorigenic cells, low NK cell function may explain the proclivity of Job's syndrome patients to viral infections and lymphoma.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.