NK Cell Deficiency In Job Syndrome Patients With Dominant Negative STAT3 Mutations

Signal transducer and activator of transcription 3 (STAT3) is an important regulator of cellular immunity, and in some animal models inhibition of STAT3 has been effective in improving natural killer (NK) cell antitumor efficacy. However, there has been little direct assessment of the STAT3 signaling role in human NK cells. In our previous work we found that (i) human NK cells stimulated with K562-based artificial antigen presenting cells (aAPC) genetically modified to express membrane bound IL-21 (mbIL21), which predominantly activates STAT3, resulted in greater proliferation, longer telomere length, and less senescence than NK cells expanded with mbIL15, which predominantly activates STAT5 (ii) NK cell proliferation, cytotoxicity and expression of the activating receptor NKG2D were enhanced by STAT3 activating cytokines and diminished by STAT3 inhibitors. Based on these results we hypothesized that activation of STAT3 plays a critical role in NK cell expansion and anti-tumor activity and tested our hypothesis by studying NK cells from Job syndrome patients. Hyper-immunoglobulin E syndrome (HIES / Job syndrome) is an immunodeficiency characterized by highly elevated serum IgE and recurrent skin and lung abscesses primarily caused by staphylococcal infection. Both, sporadic and autosomal dominant Job syndromes 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 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, proliferation and function in Job syndrome patients has not been studied yet.

We obtained peripheral blood from healthy donors and from HIES patients with documented 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 cells from normal, healthy donors were used as control. Statistical comparison was performed by Student’s t test using GraphPad Prism.

Compared to normal donors (1) Flow-cytometric analysis of PBMCs showed a significantly lower percentage of NK cells in Job syndrome patients (2) We observed impaired proliferation of Job syndrome patients’ NK cells upon stimulation of PBMCs not only with mbIL21 but also with mbIL15 in complex with its receptor α (mbIL15Rα), a physiologically relevant presentation of a physiologically relevant cytokine involved in NK cell survival and proliferation (3) Lower percentage of mature, CD56+CD16+ NK cells in Expanded NK cells from Job syndrome patients and (4) Reduced basal expression of NKG2D receptor as well as lower induction of NKG2D receptor expression upon stimulation with STAT3 activating cytokines IL10 and IL21, on Job syndrome patients’ NK cells.

Our finding of a deficient NK cell number in Job syndrome patients carrying dominant negative STAT3 mutations 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 syndrome patient’s NK cells suggest deficient development and/or deficient proliferation and survival of NK cells in Job syndrome patients with dominant negative STAT3 mutations. Along with recurrent bacterial infections, Job syndrome patients are also more prone to viral infections and lymphoma. As NK cells perform surveillance of virally infected and tumorigenic cells through NKG2D receptor, low NK cell number with reduced NKG2D expression may explain the proclivity of Job syndrome patients to viral infections and lymphoma. Work is in progress to assess cytokine generation and anti-tumor activity of Job syndrome patients’ NK cells.

No relevant conflicts of interest to declare.