Reduced frequency of peripheral CD4 + CD45RA + CD31 + cells and autoimmunity phenomena in patients affected by Del22q11 syndrome

Del22 syndrome is a complex and multisystemic embriopathy characterized by an extremely clinical heterogeneity. Patients can present cardiac anomalies, facial anomalies, hypocalcemia, palatal dysfunction, and an impaired immune function due to a defective thymic development. The majority (99.5%) of patients with Del22 syndrome have ‘partial’ defects with impaired thymic development resulting in variable defects in T-cell numbers and function. Children with Del22 have a significant risk of recurrent and severe infections and an increased risk of developing autoimmune complications that might prove important for their clinical management. The thymus plays a key role in T lymphocyte development: positive and negative selections of lymphocytes occur in the thymic cortex and medullary, respectively. To date, the mechanism by which autoimmunity occurs is unclear and it is probable that it is multifactorial. Currently, there are no immunological markers to identify or predict a higher risk of developing severe infections and autoimmune manifestations in patients with Del22 syndrome. Recent studies point to the pivotal role of RTEs (Recent Thymic Emigrants, RTEs, CD3+CD4+CD45RA+CD31+) in the regulation of T effector function, homeostasis and trafficking. The aim of this study is to describe the clinical and immunological profile in patients affected by Del22 syndrome, in order to explore whether RTEs have a role in the characterization of different clinical phenotypes. We evaluated 44 patients referred to the Pediatric Immunology Department of Anna Meyer Children’s Hospital of Florence between January 2013 and January 2017 for infections and for the presence of autoimmune disorders.