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AimsIn the present study we have investigated the comparative switching propensity of murine peritoneal and splenic B cell subpopulations to IgA in presence of retinoic acid (RA) and TGF-β.Methods and ResultsTo study the influence of RA and TGF-β on switching of B cell subpopulations to IgA, peritoneal (B1a, B1b and B2 cells) and splenic (B1a, marginal zone, and B2) B cells from normal BALB/c mice were FACS purified, cultured for 4 days in presence of RA and TGF-β and the number of IgA producing cells was determined by ELISPOT assay or FACS analysis. In presence of TGF-β, peritoneal B1b cells switched to IgA more potently than other peritoneal B cell subpopulations. When TGF-β was combined with retinoic acid (RA), switching to IgA was even more pronounced. Under these conditions, “innate” B cells like peritoneal and splenic B1 cells and MZ B cells produced IgA more readily than B2 cells. Additionally, high frequency of nucleotide exchanges indicating somatic hypermutation in VH regions was observed. Besides IgA induction, RA treatment of sorted PEC and splenic B cells led to expression of gut homing molecules - α4β7 and CCR9. Intraperitoneal transfer of RA-treated B1 cells into Rag1-/- recipients resulted in IgA in serum and gut lavage, most efficiently amongst B1b cell recipients.ConclusionPresent study demonstrates the differential and synergistic effect of RA and TGF-β on switching of different B cell subpopulations to IgA and establishes the prominence of peritoneal B1b cells in switching to IgA under the influence of these two factors. Our study extends our knowledge about the existing differences among B cell subpopulations with regards to IgA production and indicates towards their differential contribution to gut associated humoral immunity.

Chimeric antigen receptor (CAR) T cells are in prime focus of current research in cancer immunotherapy. Facilitating CAR T cell generation is among the top goals. We have recently demonstrated direct in vivo generation of human CD19-CAR T cells by targeting CD8+ cells using lentiviral vectors (LVs). The anti-tumor potency of in vivo generated CAR T cells was assessed in human PBMC-transplanted NSG mice carrying i.v. injected CD19+ Nalm-6 tumor cells. A single injection of CD8-targeted LV delivering CD19-CAR was sufficient to completely eliminate the tumor cells from bone marrow and spleen, whereas control animals contained high levels of CD19+ cells. Tumor elimination was due to in vivo generated CAR+ cells. Notably, these were not only composed of T lymphocytes but also included CAR+ natural killer cells (NK and NKT). This is the first demonstration of tumor elimination by in vivo generated human CAR T cells.

Natural killer (NK) cells are a noteworthy lymphocyte subset in cancer adoptive cell therapy. NK cells initiate innate immune responses against infections and malignancies with natural cytotoxicity, which is independent of foreign antigen recognition. Based on these substantive features, genetically modifying NK cells is among the prime goals in immunotherapy but is currently difficult to achieve. Recently, we reported a fully human CAR19 construct (huCAR19) with remarkable function in gene-modified T-cells. Here, we show efficient and stable gene delivery of huCAR19 to primary human NK cells using lentiviral vectors with transduction efficiencies comparable to those achieved with NK cell lines. These huCAR19 NK cells display specific and potent cytotoxic activity against target cells. To improve homing of NK cells to the bone marrow, we augmented huCAR19 NK cells with the human CXCR4 gene, resulting in transgenically augmented CAR NK cells (TRACKs). Compared to conventional CAR NK cells, TRACKs exhibit enhanced migration capacity in response to recombinant SDF-1 or bone marrow stromal cells while retaining functional and cytolytic activity against target cells. Based on these promising findings, TRACKs may become a novel candidate for immunotherapeutic strategies in clinical applications.

IntroductionIgA is the major class of Ab present in mucosal tissues of mammals. IgA constitutes a key defense mechanism against invasion by inhaled or ingested pathogens. IgA is also found at significant concentrations in the serum of many species, where it mediates the elimination of pathogens that have breached the mucosa [1].Among the various MALTs, IgA-producing cells are present in highest numbers in GALTs constituted by Peyer's patches (PPs), isolated lymphoid follicles (ILFs), and solitary intestinal lymphoid Correspondence: Dr. Bishnudeo Roy e-mail: Bishnudeo.Roy@helmholtz-hzi.de tissue (SILT) [2,3]. B cells, present in the B-cell follicles of such organized structures, form GCs upon Ag encounter. Under the influence of various cellular and molecular factors -T cells and cytokines, for instance -these B cells are thought to switch from IgM to IgA [4].Multiple pathways of IgA induction have been reported. The T-cell-dependent pathway of IgA induction is well known and, it is clear that IgA can also be induced in T-cell-independent (TI) manner (e.g. in T-cell-deficient mice, CD40 −/− mice, CD28 −/− mice, etc.) [5][6][7]. However, the precise contribution of T-cell-dependent and TI pathways to IgA production is not known.An important contribution of B-1 cells to TI responses has been suggested [6,8,9]. Peritoneal cavity (PEC) B-1 cells have also been claimed to contribute significantly to IgA-producing plasma cell (PC) Eur. J. Immunol. 2013Immunol. . 43: 2023Immunol. -2032. Importantly, according to phenotype, origin, and function, PEC B-1 cells can be divided into B-1a and B-1b subpopulations [12,13]. Phenotypically, B-1a cells are characterized as B220 lo CD19 hi IgM hi IgD lo CD43 + Mac-1 + CD5 int . B-1b cells share all the aforementioned markers with B-1a cells except CD5. With respect to differential contribution of these two B-1-cell subtypes to IgA production, recently, we could show that most of the IgA-secreting cells in the PEC of unmanipulated mice belonged to B-1b-cell subpopulation [14]. Additionally, IgA-derived VH regions from B-1b cells also contained frequent single nucleotide exchanges indicative of somatic hypermutation (SHM) [14]. Thus, a contribution of PEC B-1b cells to IgA production and hence to gut-associated immunity is quite likely. However, in spite of evidential suggestions for the contribution of B-1 cells to the intestinal PC pool, their contribution under unmanipulated conditions remains uncertain. This is partly due to the lack of appropriate markers to distinguish PCs according to their origin. In this context, a sequence-based approach to address this question should become very useful.In the present work, to investigate the participation of PEC B-1 cells in the gut-associated IgA production we have made use of the transgenic mouse model known as the L2 mouse line [15]. Mice of this line are characterized by the expression of a transgenic λ light chain obtained from the plasmacytoma MOPC315 (λ2 315 ). PEC of these mice contains almost exclusively CD5 + B-1a cells, whi...