Biased T-cell receptor repertoires in patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Abstract

Chromosome 22q11.2 deletion (del22q11.2) syndrome (DiGeorge syndrome/velocardiofacial syndrome) is a common syndrome typically consisting of congenital heart disease, hypoparathyroidism, developmental delay and immunodeficiency. Although a broad range of immunologic defects have been described in these patients, limited information is currently available on the diversity of the T-cell receptor (TCR) variable beta (BV) chain repertoire. The TCRBV repertoires of nine patients with del22q11.2 syndrome were determined by flow cytometry, fragment size analysis of the third complementarity determining region (CDR3 spectratyping) and sequencing of V(D)J regions. The rate of thymic output and the phenotype and function of peripheral T cells were also studied. Expanded TCRBV families were detected by flow cytometry in both CD4+ and CD8+ T cells. A decreased diversity of TCR repertoires was also demonstrated by CDR3 spectratyping, showing altered CDR3 profiles in the majority of TCRBV families investigated. The oligoclonal nature of abnormal peaks detected by CDR3 spectratyping was confirmed by the sequence analysis of the V(D)J regions. Thymic output, evaluated by measuring TCR rearrangement excision circles (TRECs), was significantly decreased in comparison with age-matched controls. Finally, a significant up-regulation in the percentage, but not in the absolute count, of activated CD4+ T cells (CD95+, CCR5+, HLA-DR+), IFN-gamma - and IL-2-expressing T cells was detected. These findings suggest that the diversity of CD4 and CD8 TCRBV repertoires is decreased in patients with del22q11.2 syndrome, possibly as a result of either impaired thymic function and/or increased T-cell activation.

Fig. 1

(a) TCRBV CDR3 spectratyping histograms in a representative patient (#9); (b) Diversity of the TCRBV repertoire analysed by CDR3 spectratyping in patients #1 to #9. The extent of TCRBV repertoire perturbation is represented as the per cent difference between the patient's CDR3 distribution and the corresponding control distribution. A value of perturbation greater than the sum of the s.d.s relative to each CDR3 length found in normal blood donors was considered abnormal. The bars on the left of the doublets represent CD4⁺ cells, and the bars on the right CD8⁺ cells. Colours denote the following: grey, abnormal pattern in CD4⁺ T cells; black, abnormal pattern in CD8⁺ T cells; white, normal pattern. The BV nomenclature adopted is from Wei et al. [42].

Fig. 2

Sequence analysis of TCRB V(D)J coding joints from two representative TCRBV families (14 and 21) of patient #9. CDR3 sequences detected more than once in each patient's sample are presented. The repertoire variability within TCRBV14, that showed a gaussian-like CDR3 profile, was 93% versus 96% in the normal (not shown) while that of TCRBV21 was 23% versus 98% in the normal (not shown). The sequence data are available from EMBL/GenBank/DDBJ

Fig. 3

(a–f). Flow-cytometric analysis of peripheral blood mononuclear cells from nine patients with chromosome 22q11.2 deletion syndrome and from nine healthy age-matched controls. Each dot corresponds to a single subject. Panels (a) to (c) show data expressed as percentage and panels (d) to (f) show data expressed as absolute count. NS, not significant.

Fig. 4

(a-b). Flow-cytometric analysis of IFN-γ -, IL-2- and IL-4-expressing T cells from nine patients with chromosome 22q11.2 deletion syndrome and from nine healthy age-matched controls. Each dot corresponds to a single subject. Panel (a) refers to data expressed as percentage and panel (b) refers to data expressed as absolute count. NS, not significant.