Hématopoïèse humaine : des cellules CD34 aux lymphocytes T

The functional relationship between hematopoietic stem cells and developing T lymphocytes

In contrast to all other blood and immune cells, T lymphocytes do not develop in the bone marrow (BM), but in the specialized microenvironment provided by the thymus. Similar to the other lineages, however, all T cells arise from multipotent hematopoietic stem cells (HSCs) that reside in the BM. Not all HSCs give rise to T cells; but how many and what kind of developmental checkpoints are located along this intricate differentiation path is the subject of intense research. Traditionally, this process has been studied almost exclusively using mouse cells, but recent advances in immunodeficient mouse models, high-speed cell sorting, lentiviral transduction protocols, and deep sequencing techniques have allowed these questions to be addressed using human cells. Here we review the process of thymic seeding by BM-derived cells and T cell commitment in humans, discussing recent insights into the clonal composition of the thymus and the definition of developmental checkpoints, on the basis of insights from human severe combined immunodeficiency patients.

[CTIP2, a multifunctional protein: cellular physiopathology and therapeutic implications]

The transcription factor CTIP2 (BCL11B) is a multifunctional protein involved in numerous cell physiological processes. To date, many molecular mechanisms underlying this process have been discovered, which highlighted the importance of the epigenetic regulation of genes and the regulation of the elongation factor P-TEFb. Furthermore studies of the deregulation of CTIP2 showed the association of CTIP2 to numerous pathologies including cancer and cardiac hypertrophy. A better comprehension of the physiopathology of these diseases might lead to the design of therapeutical strategies intending to prevent CTIP2 deregulation. Moreover, CTIP2 and its associated proteins constitute potential targets in strategies aiming to reduce and/or purge HIV-1 cell reservoirs.

Cord blood unit bankability can be predicted by prenatal sonographic parameters

OBJECTIVE

To identify possible sonographic prenatal parameters and postnatal parameters in order to obtain more bankable cord blood units (CBUs) containing a high number of primitive progenitor cells, allowing CBUs to be used as a source of haematopoietic progenitors for clinical transplantation.

STUDY DESIGN

Prospective study undertaken in the Department of Gynaecology, Obstetrics and Reproductive Science, Second University of Naples, Italy. In total, 219 unrelated CBU donors were enrolled. Ultrasound parameters (biparietal diameter, head circumference, abdominal circumference, femur length, estimation of fetal weight, umbilical artery pulsatility index), collected at hospital admission, together with birth weight and placental weight, were correlated with bankable CBU parameters (CBU volume, total nucleated cell count, CD34+ cell count).

RESULTS

Femur length and abdominal circumference correlated positively with bankable CBUs. Receiver operating curve analysis showed that these parameters can identify bankable CBUs.

CONCLUSIONS

This is the first prospective study to show the relationship between ultrasonographic fetal parameters at term and the possibility of obtaining high-quality CBUs. As such, cord blood banking could be improved worldwide by performing low-cost ultrasonographic scans.

[CXCR4, a therapeutic target in rare immunodeficiencies?]

Currently, more than 200 primary immunodeficiency diseases have been discovered. In most cases, genetic defects affect the expression or the function of proteins involved in immune development and homeostasis. Some orphan immuno-hematological disorders are characterized by an abnormal leukocyte trafficking, a notion predictive of an anomaly of the chemokine/chemokine receptor system. In this review, we focus on recent advances in the characterization of dysfunctions of the CXCL12 (SDF-1)/CXCR4 signaling axis in two rare human immunodeficiencies, one associated with a loss of CXCR4 function, the Idiopathic CD4(+) T-cell Lymphocytopenia, and the other with a gain of CXCR4 function, the WHIM syndrome.