BACKGROUND: Cord blood banks have to determine the regenerative potential of cord blood units (CBUs) on a representative sample of the cryopreserved product before release to the transplant center. Potency can be measured by using a colony-forming unit (CFU) method, which delays the release of CBU by 7 to 14 days. To accelerate CBU qualification, we have developed a rapid method to assess the response of CD34 cells to interleukin (IL)-3. Flow cytometry was used to measure IL-3-induced STAT5 phosphorylation within CD34-cells. This IL-3 test was compared to the CFU method, as well as the aldehyde dehydrogenase (ALDH) enzyme-based assay. STUDY DESIGN AND METHODS: Ten cryopreservedCBUs were analyzed for their contents in CD34 and CD45 viable cells, total CFUs, ADLH bright cells, and IL-3responsive CD34+ cells. Extreme and mild warming event scenarios were simulated on CBUs and used as poor-quality samples. Segments, tubes, and bags from five CBUs were compared for their potency using IL-3 and CFU methods.From the

The differentiation of human B lymphocytes into plasma cells is one of the most stirring questions with regard to adaptive immunity. However, the terminal differentiation and survival of plasma cells are still topics with much to be discovered, especially when targeting switched memory B lymphocytes. Plasma cells can migrate to the bone marrow in response to a CXCL12 gradient and survive for several years while secreting antibodies. In this study, we aimed to get closer to niches favoring plasma cell survival. We tested low oxygen concentrations and coculture with mesenchymal stem cells (MSC) from human bone marrow. Besides, all cultures were performed using an animal protein-free medium. Overall, our model enables the generation of high proportions of CD38+CD138+CD31+ plasma cells (≥50%) when CD40-activated switched memory B lymphocytes were cultured in direct contact with mesenchymal stem cells. In these cultures, the secretion of CXCL12 and TGF-β, usually found in the bone marrow, was linked to the presence of MSC. The level of oxygen appeared less impactful than the contact with MSC. This study shows for the first time that expanded switched memory B lymphocytes can be differentiated into plasma cells using exclusively a serum-free medium.

BACKGROUND Following solid organ or hematopoietic cell transplantation, refractory opportunistic viral reactivations are a significant cause of morbidity and mortality but can effectively be controlled by virus‐specific T‐cell transfer. Among effective and safe strategies is the use of “third‐party” (neither from the transplant donor nor recipient) virus‐specific T cells that can be manufactured from healthy donors and used as “off‐the‐shelf” therapies. Leukoreduction system chambers (LRSCs), recovered after routine plateletpheresis, were evaluated as a potential source of peripheral blood mononuclear cells (PBMCs) for the manufacturing of clinical‐scale virus‐specific T cell. STUDY DESIGN AND METHODS PBMCs from the same donors obtained either from LRSCs or peripheral blood were compared, focusing on T‐cell function and phenotype as well as the potential to generate cytomegalovirus (CMV)‐specific T‐cell lines from both CMV seropositive and seronegative donors. RESULTS PBMCs from both sources were comparable except for a transient downregulation of CD62L expression on freshly extracted PBMCs from LRSCs. Both nonspecific stimulation using anti‐CD3/CD28 antibodies and CMV peptides revealed that LRSCs or blood T cells were equivalent in terms of expansion, differentiation, and function. Moreover, PBMCs from LRSCs can be used to generate autologous monocyte‐derived dendritic cells to prime and expand CMV‐specific T cells from seronegative donors. CONCLUSION LRSCs are a reliable source of PBMCs for the generation of virus‐specific T cells for immunotherapy. These findings have implications for the development of third‐party therapeutic T‐cell products from well‐characterized blood product donors.

B lymphocyte differentiation into long-lived plasma cells is the keystone event for the production of long-term protective antibodies. CD40-CD154 and CD27-CD70 interactions are involved in human B lymphocyte differentiation into CD38hiCD138+ cells in vivo as well as in vitro. In this study, we have compared these interactions in their capacity to drive switched-memory B lymphocytes differentiation into CD38hiCD138+ plasma cells. The targeted B lymphocytes were isolated from human peripheral blood, expanded for 19 days, and then submitted to CD70 or CD154 interactions for 14 days. The expanded B lymphocytes were constitutively expressing CD39, whereas CD31's expression was noticed only following the in vitro differentiation step (day 5) and was exclusively present on the CD38hi cell population. Furthermore, the generated CD38hiCD138+ cells showed a higher proportion of CD31+ cells than the CD38hiCD138− cells. Besides, analyses done with human blood and bone marrow plasma cells showed that in vivo and de novo generated CD38hiCD138+ cells have a similar CD31 expression profile but are distinct according to their reduced CD39 expression level. Overall, we have evidences that in vitro generated plasma cells are heterogeneous and appear as CD39+ precursors to the ones present in bone marrow niches.