Biomedical subjects

Roberta Bianchi

Publications and source records attributed to Roberta Bianchi.

28 records · Page 2Linked to original sources

PubMed2003

Functional plasticity of dendritic cell subsets as mediated by CD40 versus B7 activation.

Murine dendritic cells (DCs) can present Ag in an immunogenic or tolerogenic fashion, the distinction depending on either the occurrence of specialized DC subsets or the maturation or activation state of the DC. Although DC subsets may be programmed to direct either tolerance or immunity, it is not known whether appropriate environmental stimulation can result in complete flexibility of a basic program. Using splenic CD8(-) and CD8(+) DCs that mediate the respective immunogenic and tolerogenic presentation of self peptides, we show that both the in vivo and in vitro activities of either subset can be altered by ligation of specific surface receptors. Otherwise immunogenic CD8(-) DCs become tolerogenic upon B7 ligation by soluble CTLA-4, a maneuver that initiates immunosuppressive tryptophan catabolism. In contrast, CD40 ligation on tolerogenic CD8(+) DCs makes these cells capable of immunogenic presentation. Thus, environmental conditioning by T cell ligands may alter the default function of DC subsets to meet the needs of flexibility and redundancy.

Adjuvants, Immunologic↗

PubMed2003

A defect in tryptophan catabolism impairs tolerance in nonobese diabetic mice.

The predisposition of nonobese diabetic (NOD) mice to develop autoimmunity reflects deficiencies in both peripheral and central tolerance. Several defects have been described in these mice, among which aberrant antigen-presenting cell function and peroxynitrite formation. Prediabetes and diabetes in NOD mice have been targeted with different outcomes by a variety of immunotherapies, including interferon (IFN)-gamma. This cytokine may be instrumental in specific forms of tolerance by virtue of its ability to activate immunosuppressive tryptophan catabolism. Here, we provide evidence that IFN-gamma fails to induce tolerizing properties in dendritic cells from highly susceptible female mice early in prediabetes. This effect is associated with impaired tryptophan catabolism, is related to transient blockade of the Stat1 pathway of intracellular signaling by IFN-gamma, and is caused by peroxynitrite production. However, the use of a peroxynitrite inhibitor can rescue tryptophan catabolism and tolerance in those mice. This is the first report of an experimental autoimmune disease in which defective tolerance is causally linked to impaired tryptophan catabolism.

Animals↗

PubMed2003

Subcellular localization of S100A11 (S100C) in LLC-PK1 renal cells: Calcium- and protein kinase c-dependent association of S100A11 with S100B and vimentin intermediate filaments.

The subcellular localization of the Ca(2+)-modulated protein, S100A11, was investigated in the renal cell line LLC-PK1 by immunofluorescence and confocal laser scanning microscopy under varying experimental conditions. In control cells, S100A11 was detected on the plasma membrane, where the protein co-localized with annexin I (ANXA1) at discrete sites, and found diffusely in the cytoplasm. Elevation of the cytosolic Ca(2+) concentration by means of the Ca(2+) ionophore, ionomycin, caused a significant fraction of S100A11 to associate with vimentin intermediate filament (IF)-bound S100B, another member of the S100 protein family. Under these conditions, ANXA1 underwent a quite different kind of relocation. Translocation of S100A11 onto vimentin IF-bound S100B was also observed upon activation of protein kinase C (PKC). Under these conditions, S100A11 appeared to associate directly with vimentin IFs at cell sites displaying low or no abundance of S100B such as cell processes, and, again, S100A11 and ANXA1 underwent a different relocation. Our data suggest the possibility that the intracellular Ca(2+) level might regulate the subcellular localization of S100A11 and its interaction with definite target proteins, and that S100A11 might serve the function of modulating S100B activities. Interestingly, in spite of the known ability of S100A11 to form heterotetramers with ANXA1, the two proteins underwent a different relocation on elevation of the cytosolic Ca(2+) concentration or activation of PKC, pointing to different regulatory activities of individual proteins in renal cells.

Animals↗

PubMed2003

Tryptophan catabolism in nonobese diabetic mice.

Autoimmune diseases including insulin-dependent diabetes mellitus (IDDM) are characterized by the loss of tolerance to self determinants, activation of autoreactive lymphocytes, and subsequent damage to target organs. Recent evidence suggests that the development of autoimmune diabetes in the nonobese diabetic mouse (NOD), an animal model of IDDM, is under the control of dendritic cells. The potent antigen-presenting capacity of dendritic cells can be strongly influenced by the cell maturation state and by the cytokine milieu, and in fact these cells may acquire disparate functional abilities, from immunity to tolerance. We have previously demonstrated that, in the DBA/2 mouse, IFN-gamma potentiates the tolerogenic potential of a subset of splenic dendritic cells via activation of the enzyme indoleamine 2,3-dioxygenase (IDO) and production of tryptophan catabolites capable of inducing apoptosis in T cells. In the present study, we wanted to examine whether dendritic cells from NOD mice could be subjected to regulation by proinflammatory cytokines in the same fashion as in conventional mice. We found that IFN-gamma does not potentiate the tolerogenic effects of dendritic cells from NOD mice at four weeks of age. This finding correlates with a low expression of IDO activity, thus suggesting that poor expression of IDO by dendritic cells may play a role in the development of diabetes.

Amino Acid Sequence↗

PubMed2002

Subcellular localization of S100A11 (S100C, calgizzarin) in developing and adult avian skeletal muscles.

S100A11 is a member of a multigenic family of Ca(2+)-modulated proteins of the EF-hand type. We studied the subcellular localization of S100A11 in developing and adult avian skeletal muscle cells by confocal laser scanning microscopy and immunogold cytochemistry to get information about possible functional roles of this protein. Analyses of alpha-actinin, S100A1 and S100B were done in parallel for comparison. Low levels of S100A11 were found in skeletal muscle cells at embryonic day (E) 8. At E12, S100A11 was found in myotubes in the form of fine dots located between Z-discs, and on the sarcolemma and its invaginations. At E15, S100A11 was found on the sarcolemma and internal membranes, likely longitudinal tubules, where the protein was co-localized in part with S100A1 and S100B. At E18 and afterwards, co-localization of the three S100 proteins on internal membranes was almost complete. No evidence for association of S100A11 with the contractile elements of the sarcomeres was obtained. Our data suggests that, like S100A1 and S100B, S100A11 might have a role in the regulation of membrane activities, probably in relation to Ca(2+) fluxes in skeletal muscle cells.

Animals↗

PubMed2002

CTLA-4-Ig regulates tryptophan catabolism in vivo.

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) plays a critical role in peripheral tolerance. However, regulatory pathways initiated by the interactions of CTLA-4 with B7 counterligands expressed on antigen-presenting cells are not completely understood. We show here that long-term survival of pancreatic islet allografts induced by the soluble fusion protein CTLA-4-immunoglobulin (CTLA-4-Ig) is contingent upon effective tryptophan catabolism in the host. In vitro, we show that CTLA-4-Ig regulates cytokine-dependent tryptophan catabolism in B7-expressing dendritic cells. These data suggest that modulation of tryptophan catabolism is a means by which CTLA-4 functions in vivo and that CTLA-4 acts as a ligand for B7 receptor molecules that transduce intracellular signals.

Abatacept↗

PubMed2002

CD40 ligand and CTLA-4 are reciprocally regulated in the Th1 cell proliferative response sustained by CD8(+) dendritic cells.

Subsets of murine dendritic cells (DCs) from the spleen differ in their ability to induce proliferative responses in both primary and secondary CD4(+) T cells. Recent evidence indicates that lymphoid-related CD8(+) DCs fail to provide appropriate signals to freshly isolated secondary CD4(+) T cells to sustain their proliferation in vitro. In the present study, we examined peptide-pulsed CD8(-) and CD8(+) DCs for ability to stimulate Th1 and Th2 cell clones with the same Ag specificity. Defective ability to induce proliferation was selectively shown by CD8(+) DCs presenting Ag to the Th1 clone. The deficiency in CD8(+) DCs was overcome by CD40 triggering before peptide pulsing. When exposed to CD8(+) DCs in the absence of CD40 activation, the Th1 clone expressed low levels of CD40 ligand and high levels of surface CTLA-4. Neutralization of CTLA-4 during the DC/T cell coculture resulted in increased CD40 ligand expression and proliferation of T cells. Remarkably, the activation of CD40 on DCs under conditions that would increase Th1 cell proliferation, also resulted in down-regulation of surface CTLA-4. These results confirm differential effects of CD8(+) and CD8(-) DCs in the stimulation of Ag-primed Th cells. In addition, they suggest that reciprocal regulation of CD40 ligand and CTLA-4 expression occurs in Th1 cells exposed to CD8(+) DCs.

Abatacept↗

PubMed2002

IL-23 and IL-12 have overlapping, but distinct, effects on murine dendritic cells.

IL-23 is a recently discovered heterodimeric cytokine that shares biological properties with proinflammatory cytokines. The biologically active heterodimer consists of p19 and the p40 subunit of IL-12. IL-23 has been shown to possess biological activities on T cells that are similar as well distinct from those of IL-12. We have constructed single-chain IL-23 and IL-12 fusion proteins (IL-23-Ig and IL-12-Ig) and have compared the two recombinant proteins for effects on murine dendritic cells (DC). Here we show that the IL-23-Ig can bind a significant proportion of splenic DC of both the CD8alpha(-) and CD8alpha(+) subtypes. Furthermore, IL-23and IL-12-Ig exert biological activities on DC that are only in part overlapping. While both proteins induce IL-12 production from DC, only IL-23-Ig can act directly on CD8alpha(+) DC to promote immunogenic presentation of an otherwise tolerogenic tumor peptide. In addition, the in vitro effects of IL-23-Ig did not appear to require IL-12Rbeta2 or to be mediated by the production of IL-12. These data may establish IL-23 as a novel cytokine with major effects on APC.

Amino Acid Sequence↗

PubMed2002

Mitochondrial functionality and mitochondrial DNA content in lymphocytes of vertically infected human immunodeficiency virus-positive children with highly active antiretroviral therapy-related lipodystrophy.

Mitochondria functionality and apoptosis were studied in peripheral blood lymphocytes (PBL) of human immunodeficiency virus type 1-infected children, with or without lipodystrophy (LD), who were receiving highly active antiretroviral therapy (HAART) and in PBL of healthy control subjects (HCs). By flow cytometry, mitochondrial (mt) membrane potential, mt mass, intra-mt cardiolipin distribution, and early and late apoptosis in fresh PBL or in PBL cultured with different stimuli were assessed. mtDNA content was evaluated in fresh PBL by an original double-competitive quantitative polymerase chain reaction method, which enabled direct quantification of the number of mtDNA copies present in human lymphocytes. PBL from LD-positive and LD-negative children and from HCs were similar in mt functionality and in their tendency to undergo apoptosis. mtDNA content was also similar in PBL of LD-positive children and HCs, suggesting that normal mt functionality and normal tendency to undergo apoptosis are present in PBL of children with HAART-associated LD.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Functional expression of indoleamine 2,3-dioxygenase by murine CD8 alpha(+) dendritic cells.

Immunoregulatory antigen-presenting cells (APC) play an important role in maintaining T cell homeostasis and self-tolerance. In particular, recent evidence demonstrates a role for inhibition of T cell proliferation by macrophage tryptophan catabolism involving the activity of the enzyme indoleamine 2,3-dioxygenase (IDO). Dendritic cells (DC) have also been shown to exert immunoregulatory effects mediated by tryptophan catabolism and to cause T cell apoptosis. In the present study, we have comparatively analyzed the expression of IDO activity by murine macrophages and splenic DC. By means of PCR, Western blotting and measurements of enzyme functional activity, we obtained evidence that, different from macrophages, DC constitutively express IDO. Following activation by IFN-gamma, the latter cells, in particular the CD8 alpha(+) subset, exhibit high functional activity and, unlike macrophages, mediate apoptosis of T(h) cells in vitro. Therefore, in the mouse, CD8 alpha(+) DC may be unique APC capable of fully expressing the IDO mechanism functionally.

Animals↗