Ex vivo identification and characterization of a population of CD13high CD105+ CD45- mesenchymal stem cells in human bone marrow

Introduction: Mesenchymal stem cells (MSCs) are multipotent cells capable of self-renewal and multilineage differentiation. Their multipotential capacity and immunomodulatory properties have led to an increasing interest in their biological properties and therapeutic applications. Currently, the definition of MSCs relies on a combination of phenotypic, morphological and functional characteristics which are typically evaluated upon in vitro expansion, a process that may ultimately lead to modulation of the immunophenotypic, functional and/or genetic features of these cells. Therefore, at present there is great interest in providing markers and phenotypes for direct in vivo and ex vivo identification and isolation of MSCs. Methods: Multiparameter flow cytometry immunophenotypic studies were performed on 65 bone marrow (BM) samples for characterization of CD13high CD105+ CD45- cells. Isolation and expansion of these cells was performed in a subset of samples in parallel to the expansion of MSCs from mononuclear cells following currently established procedures. The protein expre

Age Distribution of Multiple Functionally Relevant Subsets of CD4+T Cells in Human Blood Using a Standardized and Validated 14-Color EuroFlow Immune Monitoring Tube

CD4+ T cells comprise multiple functionally distinct cell populations that play a key role in immunity. Despite blood monitoring of CD4+ T-cell subsets is of potential clinical utility, no standardized and validated approaches have been proposed so far. The aim of this study was to design and validate a single 14-color antibody combination for sensitive and reproducible flow cytometry monitoring of CD4+ T-cell populations in human blood to establish normal age-related reference values and evaluate the presence of potentially altered profiles in three distinct disease models-monoclonal B-cell lymphocytosis (MBL), systemic mastocytosis (SM), and common variable immunodeficiency (CVID). Overall, 145 blood samples from healthy donors were used to design and validate a 14-color antibody combination based on extensive reagent testing in multiple cycles of design-testing-evaluation-redesign, combined with in vitro functional studies, gene expression profiling, and multicentric evaluation of manual vs. automated gating. Fifteen cord blood and 98 blood samples from healthy donors (aged 0-89 years) were used to establish reference values, and another 25 blood samples were evaluated for detecting potentially altered CD4 T-cell subset profiles in MBL (n = 8), SM (n = 7), and CVID (n = 10). The 14-color tube can identify >= 89 different CD4+ T-cell populations in blood, as validated with high multicenter reproducibility, particularly when software-guided automated (vs. manual expert-based) gating was used. Furthermore, age-related reference values were established, which reflect different kinetics for distinct subsets: progressive increase of naive T cells, T-helper (Th)1, Th17, follicular helper T (TFH) cells, and regulatory T cells (Tregs) from birth until 2 years, followed by a decrease of naive T cells, Th2, and Tregs in older children and a subsequent increase in multiple Th-cell subsets toward late adulthood. Altered and unique CD4+ T-cell subset profiles were detected in two of the three disease models evaluated (SM and CVID). In summary, the EuroFlow immune monitoring TCD4 tube allows fast, automated, and reproducible identification of >= 89 subsets of CD4+ blood T cells, with different kinetics throughout life. These results set the basis for in-depth T-cell monitoring in different disease and therapeutic conditions

Fluorochrome choices for multi-color flow cytometry

Fluorochrome selection is a key step in designing multi-color antibody panels. The list of available fluorochromes is continuously growing, fitting current needs in clinical flow cytometry to simultaneously use more markers to better define multiple leukocyte subpopulations in a single tube. Several criteria guide fluorochrome selection: i) the fluorescence profiles (excitation and emission), ii) relative brightness, iii) fluorescence overlap, iv) fluorochrome stability, and v) reproducible conjugation to antibodies. Here we used 75 samples (45 bone marrow and 30 blood) to illustrate EuroFlow strategies for evaluation of compatible fluorochromes, and how the results obtained guide fluorochrome selection as a critical step in the antibody-panel building process. Our results allowed identification of optimal fluorescence profiles (e.g. higher fluorescence intensity and/or resolution with limited fluorescence overlap into neighbor channels) for brilliant violet (BV)421 and BV510 in the violet laser and allophycocyanin (APC) hilite 7 (H7) or APC C750 in the red laser vs. other candidate fluorochromes generally applied for the same detectors and here evaluated. Moreover, evaluation of the same characteristics for another group of fluorochromes (e.g. BV605, BV650, PE CF594, AF700 or APC AF700) guided selection of the most appropriate fluorochrome conjugates to be combined in a multi-color antibody panel. Albeit this is a demanding approach, it could be successfully applied for selection of fluorochrome combinations for the EuroFlow antibody panels for diagnosis, classification and monitoring of hematological malignancies and primary immunodeficiencies. Consequently, sets of 8-, 10- and 12-color fluorochrome combinations are proposed as frame of reference for initial antibody panel design.This work was supported by CB16/12/00400 grant (CIBER-ONC, Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER) and grant PI16/00787 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain. TK and KR were supported by project NPU LO1604 and EU-Prague project CZ.2.16/3.1.00/24505

Engineered T cells secreting anti-BCMA T cell engagers control multiple myeloma and promote immune memory in vivo.

Multiple myeloma is the second most common hematological malignancy in adults and remains an incurable disease. B cell maturation antigen (BCMA)-directed immunotherapy, including T cells bearing chimeric antigen receptors (CARs) and systemically injected bispecific T cell engagers (TCEs), has shown remarkable clinical activity, and several products have received market approval. However, despite promising results, most patients eventually become refractory and relapse, highlighting the need for alternative strategies. Engineered T cells secreting TCE antibodies (STAb) represent a promising strategy that combines the advantages of adoptive cell therapies and bispecific antibodies. Here, we undertook a comprehensive preclinical study comparing the therapeutic potential of T cells either expressing second-generation anti-BCMA CARs (CAR-T) or secreting BCMAxCD3 TCEs (STAb-T) in a T cell-limiting experimental setting mimicking the conditions found in patients with relapsed/refractory multiple myeloma. STAb-T cells recruited T cell activity at extremely low effector-to-target ratios and were resistant to inhibition mediated by soluble BCMA released from the cell surface, resulting in enhanced cytotoxic responses and prevention of immune escape of multiple myeloma cells in vitro. These advantages led to robust expansion and persistence of STAb-T cells in vivo, generating long-lived memory BCMA-specific responses that could control multiple myeloma progression in xenograft models, outperforming traditional CAR-T cells. These promising preclinical results encourage clinical testing of the BCMA-STAb-T cell approach in relapsed/refractory multiple myeloma.Acknowledgments: We would like to thank the cell Sorting Service of the nUcleUS platform (University of Salamanca, Salamanca, Spain) for technical assistance. Funding: Financial support for this work was obtained from the Spanish Ministry of Science and innovation Mcin/Aei/10.13039/501100011033 (PiD2020- 115444GB- i00 to P.r.- n., PiD2019- 108160rB- i00 to P.M., Ple2021- 0075 to c.B., and PiD2020- 117323rB- 100 and PDc2021- 121711- 100 to l.Á.-V.), partially supported by the european regional Development Fund (erDF); the carlos iii health institute (iSciii) (Pi20/01030 to B.B., Pi19/00132 to l.S., Pi21- 01834 to P.P., Pi20/00822 to c.B., and DTS20/00089 to l.Á.-V.), partially supported by the erDF; the iSciii- ricorS within the next Generation eU program (plan de recuperación, Transformación y resilencia) (rD21/0017/0030 to B.B. and J.M.- l. and rD21/0017/0029 to P.M.); the iSciii- ciBeronc program (cB16/12/00400 to A.o.), the criS cancer Foundation (FcriS- 2021- 001 to J.M.- l. and FcriS- 2021- 0090 to l.Á.-V.), the Spanish Association Against cancer (Aecc) (PrYGn234975Mene to P.M., PrYGn211192BUen to c.B., and ProYe19084AlVA and PrYGn234844AlVA to l.Á.-V.); the Accelerator Award- cancer research UK/Airc/Aecc- incAr (GeAcc18001orF to A.o.), the Fundación “la caixa” (lcF/Pr/hr19/52160011 to P.M. and hr21- 00761 project il7r_lungcan to l.Á.-V.), the european research council (erc) (erc- Poc- 957466 to P.M.) and erc under the eU’s horizon Program (grant agreement 101100665 to P.M.), the Fundación de investigación Biomédica 12 de octubre (programa investiga 2022- 0082) to l.Á.-V.; the Fundación ramón Areces to P.P. l.D.-A. was supported by a rio hortega fellowship from the carlos iii health institute (cM20/00004). A.F. was supported by a postdoctoral fellowship from the Spanish Ministry of Science and innovation (FJc2021- 046789- i). A. Mayado was supported by the ciBeronc (PrF- 2869). A.P.- P. was supported by a grant from the Government of castilla y león (orden eDU/556/2019; Valladolid, Spain). M.G.- r. was supported by an industrial PhD ellowship from the comunidad de Madrid (inD2022/BMD- 23732). o.A.- S. was supported by a PhD fellowship from the complutense University of Madrid. c.D.-A. was supported by a PhD fellowship from the Spanish Ministry of Science and innovation (Pre2018- 083445). l.r.- P. was supported by a PhD fellowship from the immunology chair, Universidad Francisco de Vitoria/Merck. o.h. was supported by an industrial PhD fellowship from the comunidad de Madrid (inD2020/BMD- 17668). A.V. is supported by research institute hospital 12 de octubre (imas12). A.G.- o. is supported by hiGeA 2019/0123 Aie project to J.M.- l.S