Biomedical subjects

Lynda Bennett

Publications and source records attributed to Lynda Bennett.

7 recordsLinked to original sources

PubMed2006

Hyperthermia enhances CTL cross-priming.

Dendritic cells (DCs) loaded with killed allogeneic melanoma cells can cross-prime naive CD8(+) T cells to differentiate into melanoma-specific CTLs in 3-wk cultures. In this study we show that DCs loaded with killed melanoma cells that were heated to 42 degrees C before killing are more efficient in cross-priming of naive CD8(+) T cells than DCs loaded with unheated killed melanoma cells. The enhanced cross-priming was demonstrated by several parameters: 1) induction of naive CD8(+) T cell differentiation in 2-wk cultures, 2) enhanced killing of melanoma peptide-pulsed T2 cells, 3) enhanced killing of HLA-A*0201(+) melanoma cells in a standard 4-h chromium release assay, and 4) enhanced capacity to prevent tumor growth in vitro in a tumor regression assay. Two mechanisms might explain the hyperthermia-induced enhanced cross-priming. First, heat-treated melanoma cells expressed increased levels of 70-kDa heat shock protein (HSP70), and enhanced cross-priming could be reproduced by overexpression of HSP70 in melanoma cells transduced with HSP70 encoding lentiviral vector. Second, hyperthermia resulted in the increased transcription of several tumor Ag-associated Ags, including MAGE-B3, -B4, -A8, and -A10. Thus, heat treatment of tumor cells permits enhanced cross-priming, possibly via up-regulation of both HSPs and tumor Ag expression.

Amino Acid Sequence↗

PubMed2005

Cross-regulation of TNF and IFN-alpha in autoimmune diseases.

Cytokines, most particularly TNF and type I IFN (IFN-alphabeta), have been long considered essential elements in the development of autoimmunity. Identification of TNF in the pathogenesis of rheumatoid arthritis and TNF antagonist therapy represent successes of immunology. IFN-alphabeta plays a major role in systemic lupus erythematosus (SLE), a prototype autoimmune disease characterized by a break of tolerance to nuclear components. Here, we show that TNF regulates IFN-alpha production in vitro at two levels. First, it inhibits the generation of plasmacytoid dendritic cells (pDCs), a major producer of IFN-alphabeta, from CD34+ hematopoietic progenitors. Second, it inhibits IFN-alpha release by immature pDCs exposed to influenza virus. Neutralization of endogenous TNF sustains IFN-alpha secretion by pDCs. These findings are clinically relevant, as five of five patients with systemic juvenile arthritis treated with TNF antagonists display overexpression of IFN-alpha-regulated genes in their blood leukocytes. These results, therefore, might provide a mechanistic explanation for the development of anti-dsDNA antibodies and lupus-like syndrome in patients undergoing anti-TNF therapy.

Autoimmune Diseases↗

PubMed2005

Analysis of significance patterns identifies ubiquitous and disease-specific gene-expression signatures in patient peripheral blood leukocytes.

The utilization of gene-expression microarrays in patient-based research creates new prospects for the discovery of diagnostic biomarkers and the identification of genes or pathways linked to pathogenesis. Gene-expression signatures in peripheral blood mononuclear cells isolated from over one hundred patients with conditions presenting a strong immunological component (patient with autoimmune, graft versus host and infectious diseases, as well as immunosuppressed transplant recipients) were generated. This dataset provides the opportunity to carry out comparative analyses and define disease signatures in a broader context. Transcriptional changes of 22,283 probe sets were evaluated through statistical group comparison performed systematically for seven diseases versus their respective healthy control group. Patterns of significance were generated by hierarchical clustering of P-values. This approach led to the identification of a SLE-specific "diagnostic signature," formed by genes that did not change compared to healthy subjects in the other six diseases. Conversely, a "sentinel signature" that was common to all seven diseases was characterized. These findings bring new perspectives for the application of blood leukocyte expression signatures for diagnosis and early disease detection.

Adult↗

PubMed2003

TNF skews monocyte differentiation from macrophages to dendritic cells.

Monocytes represent a large pool of circulating precursors of APCs, both macrophages and dendritic cells (DCs). It is thus important to identify the mechanisms by which microenvironment regulates monocyte differentiation. We have previously shown that, upon contact with resting stromal cells such as fibroblasts, monocytes differentiate into macrophages in an IL-6/M-CSF-dependent fashion. Yet, in the inflamed tissue, monocytes need to yield DCs for the adaptive immunity to be induced. Inasmuch as TNF and IL-1 are present at the site of inflammation, we tested their capacity to modulate monocyte differentiation into either macrophages or DCs. TNF, but not IL-1, induce monocytes to become DCs despite the presence of fibroblasts. TNF-induced DCs contain Langerin-positive cells and are able to induce allogenic T cell proliferation. Then, TNF was found to decrease the expression and internalization of the M-CSF receptor, thus overriding the IL-6/M-CSF pathway. Thus, TNF facilitates the induction of adaptive immunity by promoting DC differentiation not only from CD34+ progenitors but also from CD14+ blood precursors.

Cell Differentiation↗

PubMed2003

Human dendritic cell subsets in NOD/SCID mice engrafted with CD34+ hematopoietic progenitors.

Distinct human dendritic cell (DC) subsets differentially control immunity. Thus, insights into their in vivo functions are important to understand the launching and modulation of immune responses. We show that nonobese diabetic/LtSz-scid/scid (NOD/SCID) mice engrafted with human CD34+ hematopoietic progenitors develop human myeloid and plasmacytoid DCs. The skin displays immature DCs expressing Langerin, while other tissues display interstitial DCs. Myeloid DCs from these mice induce proliferation of allogeneic CD4 T cells in vitro, and bone marrow human cells containing plasmacytoid DCs release interferon-alpha (IFN-alpha) upon influenza virus exposure. Injection of influenza virus into reconstituted mice triggers IFN-alpha release and maturation of mDCs. Thus, these mice may provide a model to study the pathophysiology of human DC subsets.

Animals↗

PubMed2003

Interferon and granulopoiesis signatures in systemic lupus erythematosus blood.

Systemic lupus erythematosus (SLE) is a prototype systemic autoimmune disease characterized by flares of high morbidity. Using oligonucleotide microarrays, we now show that active SLE can be distinguished by a remarkably homogeneous gene expression pattern with overexpression of granulopoiesis-related and interferon (IFN)-induced genes. Using the most stringent statistical analysis (Bonferroni correction), 15 genes were found highly up-regulated in SLE patients, 14 of which are targets of IFN and one, defensin DEFA-3, a major product of immature granulocytes. A more liberal correction (Benjamini and Hochberg correction) yielded 18 additional genes, 12 of which are IFN-regulated and 4 granulocyte-specific. Indeed immature neutrophils were identified in a large fraction of SLE patients white blood cells. High dose glucocorticoids, a standard treatment of disease flares, shuts down the interferon signature, further supporting the role of this cytokine in SLE. The expression of 10 genes correlated with disease activity according to the SLEDAI. The most striking correlation (P < 0.001, r = 0.55) was found with the formyl peptide receptor-like 1 protein that mediates chemotactic activities of defensins. Therefore, while the IFN signature confirms the central role of this cytokine in SLE, microarray analysis of blood cells reveals that immature granulocytes may be involved in SLE pathogenesis.

Child↗

PubMed2003

Dendritic cells: controllers of the immune system and a new promise for immunotherapy.

The immune system is controlled by dendritic cells (DCs). Just as lymphocytes comprise different subsets, DCs comprise several subsets that differentially control lymphocyte function. In humans, the myeloid pathway includes Langerhans cells (LCs) and interstitial DCs (intDCs). While both subsets produce IL-12, only intDCs make IL-10 and induce B cell differentiation. Another pathway includes plasmacytoid DCs, which promptly secrete large amounts of IFN-alpha/beta viral encounter. Thus, insights into in vivo DC functions are important to understand the launching and modulation of immunity.

Dendritic Cells↗