Background and Aims

Deletion of a group of genes in the 22q11 chromosome region is related to the DiGeorge phenotype characterized by the typical triad: hypocalcemia, conotruncal cardiac defects and thymic hypoplasia/aplasia. Whilst 0.5-1% of patients experience a complete phenotype with severe combined immunodeficiency, most of them present the partial phenotype characterized by a wide spectrum of mild immune abnormalities. The role of Nk cells in pDGS is unclear because of the few studies.

In 2015 Zheng described a reduced NK cell cytotoxic activity in a small group of 7 pDGS, reporting that this defect was caused by the deletion of crkL gene involved in the granule trafficking towards the immunological synapses. We attempted to confirm this defect in a larger group of patients with pDGS.

Methods

Twenty-eight patients with pDiGeorge syndorme were enrolled from January to June 2019. Steroid assumption in the previous three months and infections in the last month were the only exclusion criteria. A complete immunological study was performed, comprising immunoglobulins evaluation and lymphocyte proliferative test. NK cell activity test by was conducted in 19 patients evaluating the rate of effector cells and target K562 cells.

Results

NK cell activity was normal in 8 patients and elevated in 11 patients. The cytotoxic activity was strongly correlated to the NK cell number.

Conclusions

We could not confirm any defect of NK cell cytotoxic activity. All patients had at least an immunological abnormality (IgM reduction being the most common) that could self-explain the recurrence of respiratory tract infections observed in this group of patients.