Loss-of-function mutation in leads to immunodeficiency with dysregulated germinal center reactions and reduction of MAIT cells.

The Ikaros family transcription factors regulate lymphocyte development. Loss-of-function variants in cause primary immunodeficiency, but Ikaros family members and have not yet been associated with immunodeficiency. Here, we describe a pedigree with a heterozygous truncating variant in , encoding the transcriptional activator and repressor Helios, which is highly expressed in regulatory T cells and effector T cells, particularly of the CD8 T cell lineage.

Characterization of human T cell receptor repertoire data in eight thymus samples and four related blood samples.

T cell receptor (TCR) is a heterodimer consisting of TCRα and TCRβ chains that are generated by somatic recombination of multiple gene segments. Nascent TCR repertoire undergoes thymic selections where non-functional and potentially autoreactive receptors are removed. During the last years, the development of high-throughput sequencing technology has allowed a large scale assessment of TCR repertoire and multiple analysis tools are now also available.

Human thymic T cell repertoire is imprinted with strong convergence to shared sequences.

A highly diverse repertoire of T cell antigen receptors (TCR) is created in the thymus by recombination of gene segments and the insertion or deletion of nucleotides at the junctions. Using next-generation TCR sequencing we define here the features of recombination and selection in the human TCRα and TCRβ locus, and show that a strikingly high proportion of the repertoire is shared by unrelated individuals. The thymic TCRα nucleotide repertoire was more diverse than TCRβ, with 4.

Identifying the inheritable component of human thymic T cell repertoire generation in monozygous twins.

We have analyzed T cell receptor repertoires in a unique set of thymus samples from a pair of monozygotic twins. While genetics affect the V(D)J rearrangement and generation of junctional sequences, the thymic selections seem largely stochastic and import no detectable inheritable effect at clonal level.

Epigenetic and transcriptional analysis supports human regulatory T cell commitment at the CD4+CD8+ thymocyte stage.

The natural CD25+ FOXP3+ regulatory T cell (Treg) population is generated as a distinct lineage in the thymus, but the details of Treg development in humans remain unclear, and the timing of Treg commitment is also contested. Here we have analyzed the emergence of CD25+ cells at the CD4+CD8+ double positive (DP) stage in the human thymus. We show that these cells share T cell receptor repertoire with CD25+ CD4 single-positive thymocytes, believed to be committed Tregs.

Common gamma chain cytokines promote regulatory T cell development and survival at the CD4 CD8 stage in the human thymus.

Thymic commitment of human FOXP3 regulatory T cells begins at the double-positive (DP) CD4  CD8 stage. In the current study, we show that interleukin-2 promotes the development of FOXP3 thymocytes and enhances their survival at the DP phase. IL-2 increases the frequency of FOXP3 cells and promotes the Treg phenotype after TCR-mediated positive selection at the most mature DP stage.

T cell receptor diversity in the human thymus.

A diverse T cell receptor (TCR) repertoire is essential for adaptive immune responses and is generated by somatic recombination of TCRα and TCRβ gene segments in the thymus. Previous estimates of the total TCR diversity have studied the circulating mature repertoire, identifying 1 to 3×10(6) unique TCRβ and 0.5×10(6) TCRα sequences.

Interleukin-7 promotes human regulatory T cell development at the CD4+CD8+ double-positive thymocyte stage.

Although mature human FOXP3(+) regulatory T cells are CD127 (IL-7Rα) negative, CD4(+)CD8(+) FOXP3(+) thymocytes express relatively high levels of CD127 and are responsive to IL-7. However, the role of IL-7 in human regulatory T cell development is poorly known. We show that at the CD4(+)CD8(+) stage, FOXP3(+) thymocytes are highly susceptible to apoptosis, and IL-7 selectively rescues them from death, leading to an increased frequency of FOXP3(+) cells.