Age-determined dynamics of T-lymphocyte subpopulations in patients with 22q11.2 deletion syndrome (DiGeorge syndrome)

Patients with the 22q11.2 deletion syndrome (DiGeorge syndrome, DDS) suffer from T-cell lymphopenia, changes in function and subpopulation of T-lymphocytes. The bibliographical data conflicts on the characteristics of T-lymphocytes in patients with DDS and their changes during physiological maturation. The purpose of this research was to follow-up patients with emphasis on the dynamics of changes in T-lymphocyte subpopulations with age. Methods used: 117 patients observed during 2013-2023 who were administered at the Allergology and Immunology Department with the G.N. Speransky City Children’s Hospital No. 9 (Moscow, Russia) with a diagnosis of DDS and who had undergone blood sampling to assess T-lymphocyte subpopulations using flow cytometry. All patients (0 to 18 y/o) were divided into 4 age groups: 0 to 2 y/o, 2 to 5 y/o, 5 to 10 y/o and 10 to 18 y/o. In parallel, the blood samples of 185 apparently healthy children of the corresponding age were examined. Results: a decrease in CD3 T-lymphocytes, CD4 T-helper cells, CD8 T-cytotoxic lymphocytes, CD4 early thymic emigrants and CD4 naive T-lymphocytes was found in all age groups (p<0.05). CD8+ naive T-lymphocytes and CD8+ early thymic emigrants were reduced in all age groups, but in the 2 to 5 y/o age group their values were close to normal (p=0.072 and p=0.220, respectively). CD4+ central memory cells were elevated in all age groups (p<0.001), while CD8+ central memory cells, CD4+ and CD8+ effector memory cells differed in that they had normal values in the 2 to 5 y/o age group (p=0.229, p=0.457 and p=0.140, respectively). CD4+ TEMRA were significantly increased in the 0 to 2 y/o age group (p=0.002), and in older age groups they tended to normal values. CD8+ TEMRA did not differ from the control group and did not have age-related dynamics. The T-helper subpopulations were characterized by a significant increase in the percentage of T-helper type 1, T-helper 17, T-helper 17.1 and a decrease in T-helper type 2 compared to the population of healthy blood sample donors (p=0.001), except for patients from the 2 to 5 y/o age group. T-regulatory cells in absolute amount were reduced in all age groups (p<0.001), while their relative number corresponded to the norm in the 0 to 2 y/o age group (p=0.811) and decreased slightly in patients in older age groups, especially in the 2 to 5 y/o age group (p=0.030). Conclusion: the pathology of thymus development in patients with DDS leads to impaired maturation of T-lymphocytes, leading to an increase in the number of mature forms of T-lymphocytes, shifts towards the development of T-helper 1 and T-helper 17, and a decrease in T-regulatory cells. Disturbances in T-lymphocytes can cause changes (dysregulation) in subpopulations of B-cells. All these processes may underlie the progression of autoimmune and infectious complications in such patients that are increasing with aging.