A human postnatal lymphoid progenitor capable of circulating and seeding the thymus

Identification of a thymus-seeding progenitor originating from human bone marrow (BM) constitutes a key milestone in understanding the mechanisms of T cell development and provides new potential for correcting T cell deficiencies. We report the characterization of a novel lymphoid-restricted subset, which is part of the lineage-negative CD34+CD10+ progenitor population and which is distinct from B cell–committed precursors (in view of the absence of CD24 expression). We demonstrate that these Lin−CD34+CD10+CD24− progenitors have a very low myeloid potential but can generate B, T, and natural killer lymphocytes and coexpress recombination activating gene 1, terminal deoxynucleotide transferase, PAX5, interleukin 7 receptor α, and CD3ε. These progenitors are present in the cord blood and in the BM but can also be found in the blood throughout life. Moreover, they belong to the most immature thymocyte population. Collectively, these findings unravel the existence of a postnatal lymphoid-polarized population that is capable of migrating from the BM to the thymus

A New and Simple TRG Multiplex PCR Assay for Assessment of T-cell Clonality: A Comparative Study from the EuroClonality Consortium

T-cell Receptor Gamma (TRG) rearrangements are commonly used to detect clonal lymphoproliferations in hematopathology, since they are rearranged in virtually all T lymphocytes and have a relatively limited recombinatorial repertoire, which reduces the risk of false negative results, at the cost of potential false positivity. We developed an initial one-tube, 2-fluorochrome EuroClonality TRG PCR multiplex (TRG-1T-2F) which was compared to the original 2-tube, 2-fluorochrome EuroClonality/BIOMED-2 TRG PCR (TRG-2T-2F) and a commercial Invivoscribe one-tube, one-fluorochrome kit (IVS-1T-1F) on a series of 239 samples, including both T-cell malignancies and reactive cases. This initial assay yielded discrepant results between the 10 participating EuroClonality laboratories when using 2 fluorochromes, leading to adoption of a final single color EuroClonality strategy (TRG-1T-1F). Compared to TRG-2T-2F, both TRG-1T-1F and IVS-1T-1F demonstrated easier interpretation and a lower risk of false positive from minor peaks in dispersed repertoires. Both generate smaller fragments and as such are likely to be better adapted to analysis of formalin-fixed paraffinembedded (FFPE) tissue samples. Their differential performance was mainly explained by (i)

Expansion of Regulatory T Cells in Patients with Langerhans Cell Histiocytosis

Frederic Geissmann and colleagues find that Langerhans cell accumulation in Langerhans cell histiocytosis results from survival rather than uncontrolled proliferation, and is associated with the expansion of regulatory T cells

Immunogénétique des leucémies aiguës lymphoblastiques B

Dans les LAL B, il existe une discordance entre leur immunophénotype, par définition immature, et leur profil immunogénétique, plus mature. Nous avons étudié les caractéristiques immunogénétiques d un groupe de LAL B sans réarrangements VDJH détectable afin de savoir si i) ce profil correspond à un immunogénotype mature, ou s il est le résultat de réarrangements ongoing, ii) si des réarrangements ongoing affectent le profil des Ig et des Ig . Nos résultats montrent qu une proportion des LAL B VDJH- et DJH- a un profil immunogénétique mature avec une délétion du locus IgH, sans impact sur le profil des Ig et des Ig . L immunogénotype des LAL B ne reflète donc pas complètement celui de leur contrepartie normale, suggérant que i) la classification phénotypique des LAL B n est peut être pas représentative de l ontogénie B, ii) le système recombinase est continuellement actif dans les blastes leucémiques, sans la sélection de réarrangements fonctionnels. L éventuel caractère pronostique associé à ce profil VDJH- nécessite une étude sur un nombre de patients plus important pour être évaluable.CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF

A New and Simple TRG Multiplex PCR Assay for Assessment of T-cell Clonality: A Comparative Study from the EuroClonality Consortium

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