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Biomedical subjects

A A Manfredi

Publications and source records attributed to A A Manfredi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Blockade of the Fas-triggered intracellular signaling pathway in human melanomas is circumvented by cytotoxic lymphocytes.

Fas and Fas ligand (FasL) have been found both in lymphoid and in non-lymphoid malignancies, and are thought to play a role in the interplay between tumors and the immune system. Here we investigated Fas/FasL expression, function and intracellular signalling pathways in human melanomas. Of 5 melanoma cell lines, 3 expressed Fas at their surface, and all of them expressed FasL. FasL was functional, since it triggered Fas-induced apoptosis of human T lymphocytes clones. Conversely, cross-linking of Fas molecule with a specific monoclonal antibody failed to induce apoptosis in any of the melanomas tested, or ceramide intracellular accumulation or caspase-3 activation, pointing to an early alteration in the Fas-triggered signaling cascade. All melanomas retained the ability to undergo apoptosis induced by cytotoxic lymphocytes, which was mediated by the granule exocytosis mechanism. This suggests that melanoma cells evade immune-mediated Fas-triggered apoptosis via a selective blockade of the Fas apoptotic pathway. Cytotoxic lymphocytes, however, may circumvent tumor resistance to Fas-induced death via granzyme-mediated apoptosis, further supporting the development of immunotherapeutic strategies in the treatment of cancer.

Antigens, CD↗
PubMed1999

Dendritic cell presentation of antigens from apoptotic cells in a proinflammatory context: role of opsonizing anti-beta2-glycoprotein I antibodies.

OBJECTIVE: To verify whether opsonization of apoptotic cells skews the outcome of apoptotic cell antigen presentation by dendritic cells (DCs). METHODS: RMA cells, which were engineered with a mutant ovalbumin (OVA) protein and were devoid of the leader secretory sequence (OVA-RMA), underwent ultraviolet irradiation to induce apoptosis. Binding of anti-beta2-glycoprotein I antibodies (anti-beta2GPI) and phagocytosis of apoptotic cells were assessed by flow cytometry and confocal microscopy. Presentation of processing antigens and major histocompatibility complex (MHC) class II-restricted or MHC class I-restricted antigens was assessed using OVA-specific T cell hybridomas. RESULTS: Anti-beta2GPI facilitated presentation of epitopes from internalized apoptotic cells to MHC class II-restricted, but not to class I-restricted, T lymphocytes. DCs challenged with supernatants of apoptotic cells did not activate OVA-specific T cells, making it unlikely that anti-beta2GPI complexed with antigen released from dying cells plays a role in antigen presentation. DCs challenged with low numbers of anti-beta2GPI-opsonized apoptotic cells secreted interleukin-1beta (IL-1beta), tumor necrosis factor alpha, and IL-10 in an autocrine/paracrine manner. CONCLUSION: Opsonization influences the outcome of the disposal of low numbers of apoptotic cells by DCs. This implies that soluble factors bound to apoptotic cells modulate their immunogenicity.

Antibodies↗
PubMed1999

Delayed clearance of apoptotic lymphoma cells allows cross-presentation of intracellular antigens by mature dendritic cells.

Single cells are deleted from the midst of living tissue during normal turnover and embryogenesis. This event is not associated with inflammation or autoimmunity. Little is known of the clearance of apoptotic cells during dangerous situations, accompanied by extensive cell death and tissue damage: when macrophages are overwhelmed by apoptotic cells, other phagocytes, including immature dendritic cells (DCs), may become involved. DCs efficiently present antigens derived from the processing of internalized apoptotic bodies to class I- and class II-restricted T cells. Antigen presentation results either in T cell activation or in their functional blockade. The outcome is influenced by pro-inflammatory maturative signals: efficient T cell cross-priming requires fully mature DCs. Here we discuss in vitro data suggesting that the number of apoptotic cells that die at a given time influences DC maturation and therefore their ability to uptake antigens from apoptotic cells and cross-activate T lymphocytes.

3T3 Cells↗
PubMed1999

Central nervous system involvement in systemic lupus erythematosus patients without overt neuropsychiatric manifestations.

OBJECTIVE: To verify whether features of CNS involvement can be detected in SLE patients without overt neuropsychiatric manifestations. METHODS: 114 SLE patients who had never received a diagnosis of neuropsychiatric lupus (never-NPSLE) were studied and compared to 65 SLE patients with known neuropsychiatric involvement (NPSLE). The study relied on evaluation of neurocognitive functions by means of a battery of neuropsychological tests, on psychiatric and neuropsychological assessments and on neuroimaging studies (computed tomography, magnetic resonance, single photon emission computed tomography (SPECT)). RESULTS: Clinical features, including disease duration/activity and pharmacological therapy, of never-NPSLE and NPSLE patients were similar. Short-term and long-term memory, visuo-spatial and verbal information processing were similarly compromised in never-NPSLE and in NPSLE patients; only attention was significantly more compromised in NPSLE patients. Psychiatric morbidity was higher than expected in never-NPSLE patients, although less than in the control neuropsychiatric group. Ischemic lesions, multiple small high intensity lesions and cortical atrophy, detected by CT and MR scans, as well as abnormal SPECT were also frequently detected in never-NPSLE patients. Interestingly, left parietal and occipital area hypoperfusion by SPECT was significantly more frequent in the patients with impaired visuo-spatial intelligence and short-term memory. CONCLUSIONS: Most abnormalities detected by available diagnostic tools and characteristics of neuropsychiatric SLE are also present in non-symptomatic patients. They may derive from an unexpected widespread involvement of the CNS and are not per se sufficient, in the absence of clinical manifestations, for a diagnosis of neuropsychiatric SLE.

Adult↗
PubMed1998

Bystander apoptosis triggers dendritic cell maturation and antigen-presenting function.

Physiologic cell death via apoptosis occurs without inflammation or autoimmunity. Here, we investigated the outcome of the interaction of apoptotic cells with dendritic cells (DCs), which are potent professional APCs. DCs internalized apoptotic cells and processed them for presentation to both MHC class I- and class II-restricted T cells with an efficiency that was dependent upon the number of apoptotic cells. The latter event was accompanied by the autocrine/paracrine secretion of IL-1beta and TNF-alpha, with eventual DC maturation. High numbers of apoptotic cells, mimicking a failure of their in vivo clearance, are therefore sufficient to trigger DC maturation and the presentation of intracellular Ags from apoptotic cells, even in the absence of exogenous "danger" signals.

Animals↗
PubMed1998

Mycobacterium tuberculosis exploits the CD95/CD95 ligand system of gammadelta T cells to cause apoptosis.

Vgamma9/Vdelta2+ T cells specifically recognize Mycobacterium tuberculosis in vitro and are precociously recruited in early mycobacterial lesions. Even if gammadelta T cells are only fortuitously detected in granulomas or bronchoalveolar lavages of patients with active pulmonary tuberculosis, a role in shaping the mature alphabeta T cell response against M. tuberculosis is substantiated. Here we provide a molecular explanation for this paradox: the engagement of the gammadelta TCR by mycobacterial antigens induced the expression of CD95 ligand (CD95L) by chronically activated CD95+/CD95L- gammadelta T lymphocytes. The receptor was functional, as CD95/CD95L interaction triggered the bystander death of CD95+ cells by apoptosis. Cell death was abolished by CD95-blocking antibodies. The transient accumulation at the site of infection of CD95L+ gammadelta lymphocytes, capable of interacting with CD95+ leukocytes attracted by the response towards the pathogen, may determine the characteristics of the ensuing granulomatous disease.

Apoptosis↗
PubMed1998

Apoptotic cell clearance in systemic lupus erythematosus. I. Opsonization by antiphospholipid antibodies.

OBJECTIVE: To verify whether antiphospholipid antibodies (aPL) recognize and opsonize apoptotic human cells. METHODS: Apoptosis was induced via CD95 crosslinking or ultraviolet irradiation. IgG and anti-beta2-glycoprotein I (anti-beta2-GPI) antibodies were purified from patient sera by affinity chromatography. The aPL that bound to apoptotic cells were assessed by flow cytometry, and the subdomains recognized were identified by confocal microscopy. Human macrophages were derived from monocytes, and their ability to phagocytose 3H-labeled apoptotic bodies, whether opsonized or not opsonized by aPL, was assessed. Tumor necrosis factor alpha (TNF alpha) secretion was evaluated by enzyme-linked immunosorbent assay. RESULTS: The aPL, but not control Ig or Ig from aPL-negative patients, bound to apoptotic cells, but not to viable cells. Nuclear antigens were not recognized. Opsonization of apoptotic cells by aPL substantially enhanced recognition and binding by scavenger macrophages, with massive TNF alpha secretion. CONCLUSION: Antiphospholipid antibodies facilitate apoptotic cell clearance by macrophages and trigger TNF alpha release, possibly enhancing the immunogenicity of the autoantigens they contain.

Antibodies, Antiphospholipid↗
PubMed1998

Apoptotic cell clearance in systemic lupus erythematosus. II. Role of beta2-glycoprotein I.

OBJECTIVE: To analyze the contribution of beta2-glycoprotein I (beta2-GPI) to apoptotic cell recognition by antiphospholipid antibodies (aPL) and macrophages from patients with autoimmune disease. METHODS: Phosphatidylserine expression by Jurkat cells undergoing apoptosis upon CD95 crosslinking or ultraviolet irradiation was verified by confocal microscopy of cells stained with fluorescein isothiocyanate-labeled annexin V. Beta2-GPI was purified by heparin/cationic-exchange chromatography and was biotinylated or used to purify beta2-GPI-specific antibodies by affinity chromatography. Binding to apoptotic cells was assessed by flow cytometry. The clearance of 3H-labeled, apoptotic cells by macrophages was assessed by beta counting. RESULTS: The array of epitopes generated by beta2-GPI association with apoptotic cells specifically targets their recognition and is required for their opsonization by human aPL. Nevertheless, beta2-GPI is not required for apoptotic cell clearance by human macrophages in the absence of aPL. CONCLUSION: The proinflammatory clearance of aPL-opsonized apoptotic cells, but not the nonphlogistic clearance of apoptotic cells by scavenger macrophages, depends on beta2-GPI.

Antibodies, Antiphospholipid↗
PubMed1998

Dendritic cells preferentially internalize apoptotic cells opsonized by anti-beta2-glycoprotein I antibodies.

Dendritic cells (DC) are potent antigen-presenting cells involved in the initiation of immune responses, including those directed towards self antigens. Immature DC capture soluble antigens by macropinocytosis or c-type lectin receptor-mediated endocytosis and particulate by phagocytosis, including Fc receptor-mediated phagocytosis. Apoptosis is accompanied by the clustering of intracellular autoantigens, which are also selectively cleaved and phos-phorylated, and by the exposure of anionic phospholipids (phosphatidyl-serine, PS). Anti-phospholipid antibody (aPL) detection correlates with an increased risk of developing autoimmune syndromes. In this study apoptosis was induced by UV irradiation, growth factor deprivation or exposure to protein synthesis inhibitors of murine cells and verified by confocal microscopy and flow cytometry. Apoptotic cells were recognized by a panel of anti-beta2-glycoprotein I (beta2-GPI) aPL monoclonal antibodies, but not by isotype-matched antibodies. The binding restricted to membrane domains, corresponding to apoptotic blebs, was not affected by the stimulus initiating apoptosis and was specific, since it required the association of the beta2-GPI co-factor to the apoptotic membrane. aPL-binding successfully transformed apoptotic cells in an efficient phagocytic substrate for murine immature DC, possibly skewing their immunogenicity in vivo.

Animals↗
PubMed1998

Heterogeneity and susceptibility to apoptosis of human renal carcinoma cells in vitro.

Tumors are heterogeneous in terms of morphology and susceptibility to drugs or radiation. Among primary and metastatic cells of a human renal carcinoma, a population (type II) of larger cells with prominent nucleoli, eosinophilic globules of intermediate filaments in paranuclear bundles, margination of subcellular organelles and peripheral pools of glycogen was evident. Paranuclear structures were recognized by monoclonal antibodies specific for cytokeratin 8, 18 and 19, but not by vimentin specific antibodies. We propagated a cell line in vitro (referred to as BKR cells), and observed culture in vitro, the almost complete disappearance of the type II cells. Pharmacological agents that influence cell differentiation, such as retinoic acid, rescued the expression of type II cells in vitro. Long-term treatments with insulin or alpha-interferon, but not with the epithelial growth factor (EGF), similarly differentiated BKR cells and abated their susceptibility to spontaneous and actinomycin-D induced apoptosis. These data support the contention that differentiation of tumor cells is actively maintained in vivo and further strengthen the caveat on tumor lines stabilized in vitro, that poorly represent the morphologic and antigenic heterogeneity of neoplasms in vivo.

Apoptosis↗
PubMed1997

Processing of engulfed apoptotic bodies yields T cell epitopes.

Programmed death via apoptosis is the metazoan physiologic mode of cell death. Apoptotic cells are recognized by scavenger phagocytes via a number of membrane receptors and engulfed. Thereafter, little is known of their fate, or that of phagocytes. Here, we have traced apoptotic cells upon their engulfment by macrophages. After 3 h, apoptotic cells were contained in discrete well-defined vacuoles. Upon overnight chase, several small vesicles, possibly originating from the fragmentation of original vacuoles, were evident all over the macrophage body. Furthermore, Ags were diffused in the cytosol of some cells, which raises the possibility that epitopes from engulfed apoptotic cells may associate with macrophage MHC class I molecules and be recognized by T lymphocytes. Indeed, Ag-specific CTLs recognize and specifically lyse syngeneic macrophages upon phagocytosis of MHC class I-positive or -negative apoptotic cells, provided that they contain the relevant Ags. Synthesis and membrane expression of class I molecules by macrophages, together with functional transporters associated with Ag presentation, were necessary for recognition and lysis. The indirect presentation of epitopes from engulfed apoptotic cells by scavenger Ag-presenting phagocytes may, in the absence of "danger" signals, have implications for the establishment of central and peripheral self-tolerance.

Animals↗
PubMed1997

Autocrine nitric oxide modulates CD95-induced apoptosis in gammadelta T lymphocytes.

Gammadelta T lymphocytes play an important early role in the defense against pathogens. Their function is terminated by acquisition of susceptibility to CD95-triggered apoptosis. Here we show that the regulation of this process depends on the activity of the endothelial NO synthase expressed by gammadelta T lymphocytes, which is modulated in an activation-dependent way. The effects of nitric oxide thus generated, mediated via cGMP generation, are exerted at at least two sites along the CD95 signaling cascade: one at, or upstream, and the other downstream of ceramide generation. At either site, nitric oxide/cGMP action is sufficient for protection from apoptosis. The effect of NO is selective for apoptosis induced by CD95 cross-linking, since it does not affect apoptotic program triggered by other stimuli. The evidence here reported demonstrates a new physiological role for nitric oxide, acting as a survival factor for T lymphocytes.

Apoptosis↗
PubMed1997

Rejection of a nonimmunogenic melanoma by vaccination with natural melanoma peptides on engineered antigen-presenting cells.

Naturally processed peptides, obtained by acid extraction of tumor cells, contain Ags able to activate specific CTL in vitro. We recently reported that the nonprofessional APC, RMA-S, expressing the B7.1 molecule (RMA-S/B7), pulsed with naturally processed peptides from the nonimmunogenic B16F1 melanoma (B16F1a.e.) primed syngenic CD8+ T cells against the tumor in vitro. Here, we show the rejection of B16F1 melanoma by C57BL/6 mice after immunization with RMA-S/B7 cells pulsed with B16F1a.e. This response is critically dependent on both CD4+ and CD8+ cells, but not on NK cells. However, only CD8+ T cells exert anti-B16F1 cytolitic activity in vitro. Moreover, RMA-S/B7 cells pulsed with B16F1a.e. can be used to prevent the growth of 24-h preestablished melanomas. These results may have important implications for the clinical use of natural peptide fractions of tumor cells as therapeutic cancer vaccines.

Animals↗
PubMed1997

Quantitative cytometry of MHC class I digestion from living cells.

Digestion of crude membrane preparations with papain releases the extracellular portion of major histocompatibility complex (MHC) class I molecules. MHC class I molecules are integral membrane glycoprotein complexes formed by the noncovalent association of 2 invariant molecules, the heavy chain and the beta2-microglobulin (beta2-m), to a wide array of peptides. The cleaved soluble moiety retains the antigenic properties of the intact membrane-bound complex. Here we show that MHC class I digestion may be carried out on living cells, and we quantitate the surface expression of MHC complexes by a combined cytometric/high performance liquid chromatographic (HPLC) approach. Papain digestion results in time- and dose-dependent disappearance of membrane MHC-associated-fluorescence as detected by FACS analysis with MHC-specific monoclonal antibodies (mAbs). beta2-m and peptides became detectable by HPLC analysis and western blotting in the digestion buffer and were quantitated by comparison with purified standards. The cytometric assessment of the digestion allows one to simultaneously monitor efficacy and toxicity of the treatment. The procedure we describe allows to selectively retrieve by affinity chromatography MHC from the cell membrane, avoiding any contamination due to intracellular, "immature" MHC molecules.

Animals↗
PubMed1996

Spontaneous apoptosis of thymocytes is uncoupled with progression through the cell cycle.

Most developing lymphocytes spontaneously die in the thymus during positive and negative selection of the T cell repertoire. By evaluating the expression of the proliferation antigens Ki-67 and PCNA, we demonstrated here that more than 95% of thymocytes are potentially proliferating. The coincidence within the same cell population of death and proliferation is thus apparent in developing thymocytes. Using dual-parameter cytometric techniques to evaluate in single cells the amount of DNA versus light-scattering values, we found that spontaneous thymocyte apoptosis occurs with similar frequency in all the cycle phases, whereas apoptosis induced by the anti-topoisomerase-II, etoposide (which is the consequence of irreversible DNA damage), takes place with higher frequency in S and G2 phases (i.e., in those cycle phases in which DNA is subjected to torsional constraints). The capability of thymocytes to enter apoptosis was also monitored by digesting DNA in situ with DNase I (a nuclease that cleaves DNA mimicking the nuclear damage common to most apoptotic suicides). We also show that endonuclease-mediated DNA digestion occurs to a similar extent in cells with different DNA contents, i.e., in cycle phases in which the superstructural organization of chromatin is markedly different.

Animals↗
PubMed1996

CD95 engagement releases calcium from intracellular stores of long term activated, apoptosis-prone gammadelta T cells.

Engagement of the CD95 (Apo-1, Fas) membrane receptor is known to induce apoptosis in a variety of sensitive cells, even in the absence of extracellular Ca2+. The signal transduction events implicated in this pathway are poorly understood. We have recently characterized normal human Vgamma9/Vdelta2+ T cell clones that maintain similar levels of CD95 membrane expression throughout the culture. Here we show that 3 wk of culture after in vitro restimulation are necessary for the cells both to die and to acquire the ability to mobilize intracellular Ca2+ upon CD95 ligation. Buffering of intracellular Ca2+ by accumulation of the chelator 1,2-bis(2-amino phenoxy)ethane-N,N,N1,N-tetraacetic acid protects from CD95-triggered apoptosis, suggesting that the two phenomena are causally related. As intracellular Ca2+ release by inhibition of endoplasmic reticulum ATPases induces apoptosis in both recently and long term activated gamma delta cells, the molecular regulation of activation-dependent apoptosis is likely to involve events upstream of CD95-dependent Ca2+ release. The CD95-triggered increase in the intracellular Ca2+ concentration depends on depletion of the same intracellular Ca2+ stores mobilized by ligation of the TCR, and Ca2+ release does not depend on inositol 1,4,5-trisphosphate generation.

Apoptosis↗
PubMed1996

Particulate naturally processed peptides prime a cytotoxic response against human melanoma in vitro.

For an efficient antitumor cytotoxic response, tumor antigenic peptides need to be presented by professional antigen-presenting cells in association with MHC class I molecules. We established in vitro short-term human CTL lines from healthy and melanoma-bearing subjects, using as antigen-presenting cells autologous adherent cells after phagocytosis of latex beads coated with melanoma peptides. Melanoma peptides were obtained by acid extraction of melanoma cells that matched with donor peripheral blood mononuclear cells, at least for one HLA-A allele. The cytotoxic activity of the lines was specific for the melanoma from which peptides were obtained and for melanoma sharing HLA alleles. These results demonstrate that a complex mixture of naturally processed melanoma peptides conjugated to a phagocytic substrate that targets them into the MHC class I pathway of adherent cells can prime a CTL response in healthy subjects in vitro, and that peptides from allogeneic tumors may be used to propagate CTL in melanoma patients. Our data support the feasibility of active and passive vaccination procedures with nonliving vaccines in cancer patients.

Animals↗