Biomedical subjects

Deepta Bhattacharya

Publications and source records attributed to Deepta Bhattacharya.

6 recordsLinked to original sources

PubMed2006

Rapid lymphocyte reconstitution of unconditioned immunodeficient mice with non-self-renewing multipotent hematopoietic progenitors.

The replacement of abnormal hematopoietic stem cells (HSCs) with normal transplanted HSCs can correct a wide range of hematologic disorders. Here, we provide evidence that transplantation of more differentiated progenitor cells can be used to more rapidly correct lymphoid deficiencies in unconditioned immunocompromised mice. Transplantation of flk2+ multipotent progenitors led to robust B and T cell reconstitution that was maintained for at least 16 weeks. Antigenic challenge at 16 weeks post-transplantation revealed that reconstituted lymphocytes maintained a functional repertoire. In contrast to the persistent lymphocytic engraftment, myeloid chimerism was lost by 12 weeks post-transplantation consistent with the fact that flk2+ progenitors are non-self-renewing. Thus, while more differentiated progenitors are capable of rescuing lymphoid deficiencies, transplantation of HSCs must be used for the correction of non-lymphoid disorders, and, we propose, very long-term immune reconstitution. Based on recent evidence, we discuss novel strategies to achieve the replacement of abnormal HSCs without the use of cytotoxic conditioning regimens.

Animals↗

PubMed2006

Memory T and memory B cells share a transcriptional program of self-renewal with long-term hematopoietic stem cells.

The only cells of the hematopoietic system that undergo self-renewal for the lifetime of the organism are long-term hematopoietic stem cells and memory T and B cells. To determine whether there is a shared transcriptional program among these self-renewing populations, we first compared the gene-expression profiles of naïve, effector and memory CD8(+) T cells with those of long-term hematopoietic stem cells, short-term hematopoietic stem cells, and lineage-committed progenitors. Transcripts augmented in memory CD8(+) T cells relative to naïve and effector T cells were selectively enriched in long-term hematopoietic stem cells and were progressively lost in their short-term and lineage-committed counterparts. Furthermore, transcripts selectively decreased in memory CD8(+) T cells were selectively down-regulated in long-term hematopoietic stem cells and progressively increased with differentiation. To confirm that this pattern was a general property of immunologic memory, we turned to independently generated gene expression profiles of memory, naïve, germinal center, and plasma B cells. Once again, memory-enriched and -depleted transcripts were also appropriately augmented and diminished in long-term hematopoietic stem cells, and their expression correlated with progressive loss of self-renewal function. Thus, there appears to be a common signature of both up- and down-regulated transcripts shared between memory T cells, memory B cells, and long-term hematopoietic stem cells. This signature was not consistently enriched in neural or embryonic stem cell populations and, therefore, appears to be restricted to the hematopoeitic system. These observations provide evidence that the shared phenotype of self-renewal in the hematopoietic system is linked at the molecular level.

B-Lymphocytes↗

PubMed2006

Hematopoietic stem cells: expression profiling and beyond.

This review focuses on the genomics of mouse hematopoiesis, but also draws parallels to other systems and discusses issues common to the analysis of rare populations such as stem cells. As examples from the mouse blood forming system are used to illustrate several points, the authors first give a brief introduction to mouse hematopoiesis as a model system. We review the multiple microarray analyses that have been performed on various mouse hematopoietic subpopulations and comment on both technical and biological aspects of such experiments. The concept of stemness is discussed, and the importance of biological function of gene products, protein-protein interactions and molecular pathways highlighted. Finally, the authors discuss some major unresolved issues in hematopoiesis and discuss the potential uses of future microarray analysis as well as other genomic and functional approaches that might prove useful to further our understanding of hematopoiesis and other stem cell systems.

Animals↗

PubMed2005

Purified hematopoietic stem cell engraftment of rare niches corrects severe lymphoid deficiencies without host conditioning.

In the absence of irradiation or other cytoreductive conditioning, endogenous hematopoietic stem cells (HSCs) are thought to fill the unique niches within the bone marrow that allow maintenance of full hematopoietic potential and thus prevent productive engraftment of transplanted donor HSCs. By transplantation of purified exogenous HSCs into unconditioned congenic histocompatible strains of mice, we show that approximately 0.1-1.0% of these HSC niches are available for engraftment at any given point and find no evidence that endogenous HSCs can be displaced from the niches they occupy. We demonstrate that productive engraftment of HSCs within these empty niches is inhibited by host CD4+ T cells that recognize very subtle minor histocompatibility differences. Strikingly, transplantation of purified HSCs into a panel of severe combined immunodeficient (SCID) mice leads to a rapid and complete rescue of lymphoid deficiencies through engraftment of these very rare niches and expansion of donor lymphoid progenitors. We further demonstrate that transient antibody-mediated depletion of CD4+ T cells allows short-term HSC engraftment and regeneration of B cells in a mouse model of B(-) non-SCID. These experiments provide a general mechanism by which transplanted HSCs can correct hematopoietic deficiencies without any host conditioning or with only highly specific and transient lymphoablation.

Aging↗

PubMed2002

Identification of gene function by cyclical packaging rescue of retroviral cDNA libraries.

Genes regulating responses in mammalian cells are often difficult to identify by functional cloning strategies limited to a single round of selection. Here we describe a strategy, cyclical packaging rescue (CPR), which allows rapid recovery and retransmission of retroviral cDNA libraries. CPR can be used not only with immortalized cell lines such as fibroblasts and Jurkat T cells, but also with primary B lymphocytes, which can be maintained only in short-term cultures. CPR allows for multiple rounds of selection and enrichment to identify cDNAs regulating responses in mammalian cells. Using CPR, five cDNAs were functionally cloned, which conferred protection against tumor necrosis factor alpha (TNFalpha)-induced apoptosis in RelA(-/-) fibroblasts. Three of the genes, RelA, cellular FLICE-like inhibitory protein (c-FLIP), and a dominant-negative mutant of TNF receptor 1 arising through CPR afforded strong protection against apoptosis. Two of the genes identified, Dbs and Fas-associated death domain protein (FADD), previously identified as a proapoptotic molecule, afforded partial protection against TNFalpha-induced apoptosis. These results suggest that CPR is a versatile method that permits functional identification of both wild-type and dominant-negative gene products that regulate cellular responses.

Base Sequence↗

PubMed2002

Regulation of Ig class switch recombination by NF-kappaB: retroviral expression of RelB in activated B cells inhibits switching to IgG1, but not to IgE.

Mutant NF-kappaB-deficient B cells from knockout mice lacking RelA, p105/p50 or the transactivation domain of c-Rel exhibit distinct and selective cell-intrinsic defects in their ability to undergo class switch recombination (CSR) to specific Ig isotypes. This isotype-specific requirement for particular NF-kappaB transcription factors in B cells activated to undergo CSR is intriguing because the NF-kappaB composition in B cells is also highly regulated and can vary significantly depending upon how B cells are activated. These studies prompted us to test by retroviral transduction of normal B cells whether changes in the NF-kappaB composition in activated B cells could modulate cytokine-driven CSR. RelB, RelA, c-Rel, p50 and p52 were first expressed in lipopolysaccharide-activated primary B cells and then induced by cytokine addition to undergo CSR to IgG1, IgE, IgG2a, IgG2b or IgA. Surprisingly, only retroviral expression of RelB altered CSR, resulting in a 3-fold decrease in CSR to IgG1 induced by IL-4. This effect was isotype specific as RelB expression did not affect CSR to IgE within the same culture or to other isotypes tested. The transactivation domain of RelB was required for inhibition of CSR to IgG1. Expression of p50-RelB or p52-RelB dimers joined covalently by a flexible peptide linker also specifically inhibited IgG1 CSR. RelB-mediated inhibition of IgG1 CSR was associated with a decrease in germline gamma1 transcription, but not with changes in proliferation as assayed by CFSE labeling. Thus, RelB complexes can specifically inhibit CSR to IgG1, but not IgE, in activated, primary B cells.

Animals↗