Absolute numbers of CD4⁺ and CD8⁺ T cells, CD19⁺ B cells and CD3⁻CD16/56⁺ NK cells over time. (A) Numbers of the patient's lymphocytes are indicated in closed circles; the age-matched control levels for different age categories (ie, 4-10 years; 10-18 years) are indicated in a range of ± 2SD (dotted lines). (B) Immunophenotyping of CD4⁺ and CD8⁺ T cells and CD19⁺CD20⁺ B cells, according to CD45RA/CD27 and sIgD/CD27, respectively, as compared with a healthy, age-matched control. Proliferative capacity of the patient's T cells. T-cell proliferation of the patient and a healthy control is shown by CFSE dilution after 6 days of culture. Polyclonal proliferation was induced by a combination of CD3/CD28 or IL-15, whereas antigen-specific proliferation was assessed by stimulation with tetanus toxoid (Tet Tox), cytomegalovirus (CMV) or varicella zoster virus (VZV). (C) As expected in the presence of negative serology, CMV antigen did not activate her T cells. Increased proliferation of the peripheral CD4⁺ T-cell compartment as demonstrated by nuclear Ki67 staining in naive (CD45RA⁺CD27⁺) CD4⁺ and CD8⁺ T cells, compared with healthy age-matched naive control T cells, as described.¹³  TRECs in patient's T cells for the early, so-called signal joint (Sj) over a period of 5 years. (D) For T-cell repertoire analysis CDR3 spectratyping in the patient's T cells was analyzed, being representative for 2 separate experiments in triplicate, more than 2 years apart.