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PubMed2002

Adrenomedullin has multiple roles in disease stress: development and remission of the inflammatory response.

The upregulation of adrenomedullin (AM) gene expression and increases in systemic circulatory as well as localized tissue AM concentrations is well coordinated with the onset and progression of trauma, infection, and sepsis. As such, the coordinated change in AM suggests a key role for this peptide in the inflammatory response. By clinical definition, the process of inflammation constitutes an orchestrated cascade of localized tissue and systemic responses to immunological challenges. Classical responses to the onset of disease stresses are manifested in the timely elaboration of humoral, blood-borne signal effectors (such as adrenocortical and locally produced tissue hormones, immune cytokines, and inorganic signals such as nitric oxide) as well as patterned migration and infiltration of circulating bone marrow-derived cells (mononuclear cells such as monocyte-macrophages and polymorphonuclear cells like neutrophils) largely associated with or delivered through the vascular system. The body's attempts to combat acute infection to restore homeostatic equilibrium are further compromised by underlying disease situations. Atherosclerosis, diabetes, and cardiovascular disease, as well as nutritional metabolic derangements and persistent subclinical infection perturb the regulatory feedback loops necessary for proper control of response effectors like hormones and cytokines. When imbalances occur, tissue necrosis can ensue as driven by free radical damage to cell components. A true appreciation of the inflammatory response can only be grasped through an integrative approach in which the relationship between the different physiological systems is viewed in terms of a changing, dynamic interaction. In essence, the inflammatory response can be thought of in three phases: a period of severity assessment, a period of remediation, and a period of homeostatic restoration. Indeed, AM has differential effects on cellular metabolism, immune function, endocrine function, and cardiovascular function. This peptide appears to play a pivotal role in both reprioritizing the biological needs of tissues and organs during the three phases of inflammatory response as well as a role in restoring homeostatic equilibrium to the body.

Adrenomedullin↗
PubMed1999

Outcome prediction by traditional and new markers of inflammation in patients with sepsis.

Patients (n=242) admitted to intensive care unit for longer than 48 hours were categorised for sepsis according to American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) Consensus Conference criteria. Body temperature, leukocyte count, C-reactive protein (CRP) and procalcitonin (PCT) as well as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, IL-10 and HLA-DR expression on monocytes were determined. Data of one randomly chosen day per patient entered analysis. Immunologic mediators contributing significantly to outcome were determined by logistic regression analysis. Area under the curves (AUC) of receiver operating characteristic curves of clinical markers of inflammation predicting prognosis were compared with AUC of relevant immunologic mediators. TNF-alpha, IL-6 and HLA-DR expression on monocytes were significantly associated with outcome; the AUC's were 0.835, 0.844 and 0.761 respectively. AUC's for clinical markers were 0.878, 0.811, 0.620 and 0.614 for PCT, CRP, leukocyte count and body temperature respectively. PCT had the highest AUC compared to other clinical markers. These data indicate that PCT might be a better marker than the classic criteria of inflammation, CRP, leukocyte count, and body temperature to identify patients endangered by severe infection or sepsis.

Adult↗
PubMed2006

CD40 ligand binds to alpha5beta1 integrin and triggers cell signaling.

It was originally thought that the critical role of the CD40 ligand (CD40L) in normal and inflammatory immune responses was mainly mediated through its interaction with the classic receptor, CD40. However, data from CD40L(-/-) and CD40(-/-) mice suggest that the CD40L-induced inflammatory immune response involves at least one other receptor. This hypothesis is supported by the fact that CD40L stabilizes arterial thrombi through an alphaIIbbeta3-dependent mechanism. Here we provide evidence that soluble CD40L (sCD40L) binds to cells of the undifferentiated human monocytic U937 cell line in a CD40- and alphaIIbbeta3-independent manner. Binding of sCD40L to U937 cells was inhibited by anti-CD40L monoclonal antibody 5C8, anti-alpha5beta1 monoclonal antibody P1D6, and soluble alpha5beta1. The direct binding of sCD40L to purified alpha5beta1 was confirmed in a solid phase binding assay. Binding of sCD40L to alpha5beta1 was modulated by the form of alpha5beta1 expressed on the cell surface as the activation of alpha5beta1 by Mn(2+) or dithiothreitol resulted in the loss of sCD40L binding. Moreover, sCD40L induced the translocation of alpha5beta1 to the Triton X-100-insoluble fraction of U937 cells, the rapid activation of the MAPK pathways ERK1/2, and interleukin-8 gene expression. The binding of sCD40L to CD40 on BJAB cells, an alpha5beta1-negative B cell line, and the resulting activation of ERK1/2 was not inhibited by soluble alpha5beta1, suggesting that sCD40L can bind concomitantly to both receptors. These results document the existence of novel CD40L-dependent pathways of physiological relevance for cells expressing multiple receptors (CD40, alpha5beta1, and alphaIIbbeta3) for CD40L.

Animals↗
PubMed1985

Acute phase response in infectious disease.

In considering the pathology associated with infectious diseases, the most common host response to such infection is inflammation. The mechanism(s) whereby inflammation is initiated and the cell types involved will dictate the kinds of acute phase plasma changes that can be seen associated with the infection. Bacteria seem to initiate the classical type of inflammatory response and plasma protein changes similar to those seen in experimental inflammation induced by chemical means. Viruses, on the other hand, in the absence of cytopathology do not appear to induce the same kind of inflammatory changes and avoid the induction of the acute phase protein response since they may not initiate activation of monocytes and/or macrophages. Those viruses that do cause macrophage activation would be expected to have acute phase protein changes associated with that activation. Parasites, however, appear to initiate the acute phase plasma response only when their migration leads to tissue destruction and local inflammation such as caused by parasitemia with Trypanosoma cruzi in the mouse or with migration of Nippostrongylus brasiliensis in the rodent. Human parasitic diseases require much more investigation in order to clarify the role played by acute phase proteins in the subsequent establishment of the host-parasite relationship. We postulate that the macrophage or monocyte on interaction with the infectious pathogen becomes activated and secretes a number of factors, including interleukin 1 and hepatocyte-stimulating factor, which have a marked effect on the total acute phase reaction. In addition to an effect on phagocytic and immune systems, the mediators cause hepatocytes to markedly increase the secretion of plasma acute phase proteins. Some of these proteins return to the site of inflammation and interact with the infectious pathogen and/or cells and proteins of the host, thereby affecting the final outcome of inflammation. We also propose that the initial interaction of an organism such as a parasite and the mammalian host involves early recognition by the macrophage, thereby initiating both the humoral and cellular acute phase reactions and subsequently affects the immune response against the parasite. Variations in the acute phase reaction may help to explain differences in susceptibility to infectious organisms and the presence or lack of host killing mechanisms for the parasite.

Acute-Phase Proteins↗
PubMed1991

Immunohistology of human allergic late-phase skin reactions.

Human late-phase allergic skin reactions (LPSR) are characterised histologically by a mixed infiltrate of granulocytes and mononuclear cells. Quantitative immunohistology reveals a correlation between the numbers of CD4+ T-cells and the number of activated eosinophils at LPSR sites. These CD4+ T-cells are predominantly CD45RO+ and belong to the 'memory' T-cell subset. Immunofluorescence studies indicate that type III (immune complex) mechanisms make no significant contribution to the LPSR. On the other hand, the LPSR and classical delayed-type hypersensitivity (DHT) both have a marked CD4+ T-cell component. T-cell infiltration is a more diffuse process in DTH than in the LPSR; between 24 and 48 h, DTH sites show a further increase in T-cell numbers with the appearance of CD8+ T-cells and an influx of monocytes. Activated eosinophils are present in the early stages of both LPSR and DTH, but are more prominent in the LPSR. These different patterns of cellular infiltration and activation are probably due to differences in the cytokine secretion pattern of the infiltrating T-cells. Detailed analysis of this hypothesis will require the use of in situ hybridization techniques.

Eosinophils↗
PubMed2004

Effect of complement inhibition and heparin coating on artificial surface-induced leukocyte and platelet activation.

BACKGROUND: Exposure of blood to artificial surfaces, as in cardiopulmonary bypass, induces an inflammatory response involving complement, leukocyte and platelet activation. To elucidate the specific role of complement in this process, studies were performed on blood circulated in polyvinyl chloride tubing in the absence and presence of complement inhibitors. Parallel experiments were performed with heparin-coated polyvinyl chloride tubing, which is known to prevent complement and cell activation. METHODS: A novel experimental model was used, based on human whole blood anticoagulated with lepirudin. Complement activation products, myeloperoxidase, lactoferrin, and thrombospondin were quantified in enzyme immunoassays. Leukocyte CD11b expression and leukocyte-platelet conjugates were detected by flow cytometry. RESULTS: Increased levels of C3 activation products, alternative pathway convertase, and the terminal SC5b-9 complex, combined with unchanged levels of C1rs-C1-inhibitor complexes and marginal changes in C4 activation demonstrated that complement was activated through the alternative pathway. Granulocyte and monocyte CD11b expression and granulocyte-platelet conjugate formation were efficiently attenuated by blocking either factor D, C3, C5, or C5a receptor. In contrast, monocyte-platelet conjugate formation and release of myeloperoxidase, lactoferrin, and thrombospondin were not reduced by complement inhibition. Heparin-coated polyvinyl chloride tubing efficiently reduced all inflammatory markers studied, except for C1rs-C1-inhibitor complexes, which increased, consistent with the enhancing effect of heparin on C1-inhibitor function. This effect did not, however, reduce fluid-phase classic pathway activation induced by heat-aggregated immunoglobulin G. CONCLUSIONS: Leukocyte and platelet activation in response to artificial materials occur by mechanisms that vary in their dependence on complement. Heparin coating precludes both the complement-dependent and complement-independent reactions.

CD11 Antigens↗
PubMed2001

Human relaxin gene 3 (H3) and the equivalent mouse relaxin (M3) gene. Novel members of the relaxin peptide family.

We have identified a novel human relaxin gene, designated H3 relaxin, and an equivalent relaxin gene in the mouse from the Celera Genomics data base. Both genes encode a putative prohormone sequence incorporating the classic two-chain, three cysteine-bonded structure of the relaxin/insulin family and, importantly, contain the RXXXRXX(I/V) motif in the B-chain that is essential for relaxin receptor binding. A peptide derived from the likely proteolytic processing of the H3 relaxin prohormone sequence was synthesized and found to possess relaxin activity in bioassays utilizing the human monocytic cell line, THP-1, that expresses the relaxin receptor. The expression of this novel relaxin gene was studied in mouse tissues using RT-PCR, where transcripts were identified with a pattern of expression distinct from that of the previously characterized mouse relaxin. The highest levels of expression were found in the brain, whereas significant expression was also observed in the spleen, thymus, lung, and ovary. Northern blotting demonstrated an approximately 1.2-kb transcript present in mouse brain poly(A) RNA but not in other tissues. These data, together with the localization of transcripts in the pars ventromedialis of the dorsal tegmental nucleus of C57BLK6J mouse brain by in situ hybridization histochemistry, suggest a new role for relaxin in neuropeptide signaling processes. Together, these studies describe a third member of the human relaxin family and its equivalent in the mouse.

Amino Acid Sequence↗
PubMed2006

Receptor-type protein tyrosine phosphatase gamma (PTPgamma), a new identifier for myeloid dendritic cells and specialized macrophages.

Protein tyrosine phosphatase (PTPgamma) is a receptor-like molecule with a known role in murine hematopoiesis. We analyzed the regulation of PTPgamma expression in the human hematopoietic system, where it was detected in human peripheral blood monocytes and dendritic cells (DCs) of myeloid and plasmacytoid phenotypes. Its expression was maintained during in vitro monocyte differentiation to dendritic cells (moDC) and was further increased after maturation with bacterial lipopolysaccharide (LPS), CD40L, and TNFalpha. But PTPgamma was absent when monocytes from the same donor were induced to differentiate in macrophages. B and T lymphocytes did not express PTPgamma. Rather, PTPgamma mRNA was expressed in primary and secondary lymphoid tissues, and the highest expression was in the spleen. PTPgamma was detected by immunohistochemistry in subsets of myeloid-derived DCs and specialized macrophages (tingible bodies, sinus and alveolar macrophages). Classic macrophages in infective or reactive granulomatous reactions did not express PTPgamma. Increased PTPgamma expression was associated with a decreased ability to induce proliferation and interferon-gamma secretion in T cells by moDCs from patients with advanced pancreatic cancer. Taken together, these results indicate that PTPgamma is a finely regulated protein in DC and macrophage subsets in vitro and in vivo.

Aged↗
PubMed1998

Alternative macrophage activation-associated CC-chemokine-1, a novel structural homologue of macrophage inflammatory protein-1 alpha with a Th2-associated expression pattern.

We have cloned a novel human CC-chemokine, alternative macrophage activation-associated CC-chemokine (AMAC)-1. The isolated cDNA clone (803 bp) shows a single open reading frame of 267-bp coding for 89 amino acid residues; mature AMAC-1 protein is predicted to consist of 69 amino acids with a m.w. of 7855. Sequence alignment and 3D-modeling show the typical structural characteristics of CC-chemokines with special features in the receptor-activating domain. AMAC-1 is most closely related to MIP-1 alpha with a cDNA and protein sequence homology of 55% and 59%, respectively. However, the expression pattern of AMAC-1 is directly opposite to that of MIP-1 alpha. While MIP-1 alpha is induced by classical macrophage mediators such as LPS and is inhibited by IL-4 and glucocorticoids, AMAC-1 is specifically induced in macrophages by alternative macrophage mediators such as IL-4, IL-13, and IL-10. Expression of AMAC-1 is inhibited by IFN-gamma while glucocorticoids exert a slightly positive synergistic effect in combination with IL-4. Peripheral blood monocytes do not express AMAC-1; time course experiments show that monocyte-to-macrophage differentiation is a prerequisite for AMAC-1 expression. Expression of AMAC-1 by granulocyte-macrophage CSF/IL-4-induced, monocyte-derived dendritic cells is complex; in mature adherent dendritic cells, however, only minor AMAC-1 mRNA expression was found. In vivo, AMAC-1 is expressed by alveolar macrophages from healthy persons, smokers, and asthmatic patients. In conclusion, AMAC-1 is a novel CC-chemokine whose expression is induced in alternatively activated macrophages by Th2-associated cytokines; thus, AMAC-1 may be involved in the APC-dependent T cell development in inflammatory and immune reactions.

Amino Acid Sequence↗
PubMed2005

Polarized monocyte response to cytokine stimulation.

BACKGROUND: Mononuclear phagocytes (MPs) stand at the crossroads between the induction of acute inflammation to recruit and activate immune effector cells and the downmodulation of the inflammatory process to contain collateral damage. This decision is extensively modulated by the cytokine microenvironment, which includes a broad array of cytokines whose direct effect on MPs remains largely unexplored. Therefore, we tested whether polarized responses of MPs to pathogens are related to the influence of selected cytokines or represent a mandatory molecular switch through which most cytokines operate. RESULTS: Circulating CD14+ MPs were exposed to bacterial lipopolysaccharide (LPS) followed by exposure to an array of cytokines, chemokines and soluble factors involved in the immune response. Gene expression was studied by global transcript analysis. Two main classes of cytokines were identified that induced a classical or an alternative pathway of MP activation. Expression of genes affected by NFkappaB activation was most predictive of the two main classes, suggesting that this pathway is a fundamental target of cytokine regulation. As LPS itself induces a classical type of activation, the most dramatic modulation was observed toward the alternative pathway, suggesting that a broad array of cytokines may counteract the pro-inflammatory effects of bacterial components. CONCLUSIONS: This analysis is directly informative of the primary effect of individual cytokines on the early stages of LPS stimulation and, therefore, may be most informative of the way MP maturation may be polarized at the early stages of the immune response.

Adult↗
PubMed1999

Lymphocyte-specific protein 1: a specific marker of human leucocytes.

While both murine and human homologues of the LSP1 gene (lymphocyte-specific gene 1) and its protein products have been identified, studies on human LSP1 have been limited. The present report describes a detailed immunocytochemical study of the distribution and localization of human LSP1 in both normal and neoplastic cells and tissues. The specificity of the monoclonal anti-LSP1 reagent was confirmed by expression cloning and transfection studies. The intracellular 60 000 MW LSP1 protein was found to be present in peripheral blood B cells, monocytes and granulocytes but absent in a subpopulation of circulating T cells (10-15% of CD3-positive T cells). The presence of LSP1 protein in medullary thymocytes, but only in scattered cortical thymocytes, provided additional evidence for heterogeneity of expression in T cells. Novel observations also included the presence of LSP1 in plasma cells, dendritic cells and Langerhans' cells. The leucocyte-restricted distribution of LSP1 protein means that it may play an important role in haematopathology. LSP1 protein was detected in a wide range of leukaemias and lymphomas, particularly of B-cell origin, and in tumour cells in classical Hodgkin's disease. Of interest was the indication of a reciprocal relationship in the expression of LSP1 and ALK (anaplastic lymphoma kinase) proteins in patients with anaplastic large cell lymphoma. As the anti-LSP1 reagent used in the present study recognizes a formalin-resistant epitope it should be of considerable value in the diagnosis of routinely fixed material.

Anaplastic Lymphoma Kinase↗
PubMed1999

Molecular and functional characterization of IRp60, a member of the immunoglobulin superfamily that functions as an inhibitory receptor in human NK cells.

In this study we describe the functional and molecular characterization of IRp60 (inhibitory receptor protein 60), an inhibitory receptor expressed on all human NK cells. The IRp60 molecule has been identified by the generation of three novel monoclonal antibodies (mAb). Cross-linking of IRp60 by specific mAb strongly inhibits the spontaneous cytotoxicity of NK cells as well as the NK-mediated cytolytic activity induced via different non-HLA-specific or HLA-specific activating receptors. IRp60 is a 60-kDa glycoprotein that, upon sodium pervanadate treatment, becomes tyrosine phosphorylated and associates with the SH2-containing phosphatases SHP-1 and SHP-2. The IRp60 gene is located on human chromosome 17 and encodes a molecule belonging to the immunoglobulin (Ig) superfamily characterized by a single V-type Ig-like domain in the extracellular portion. The cytoplasmic tail contains three classical immunoreceptor tyrosine-based inhibitory motifs. Southern blot analysis revealed cross-hybridization with monkey and mouse genomic DNA, thus suggesting that IRp60 may be conserved among different species. Moreover, based on the use of different anti-IRp60 mAb, we could identify two IRp60 allelic variants. Since IRp60 is also expressed by other cell types, including T cell subsets, monocytes and granulocytes, it may play a more general role in the negative regulation of different leukocyte populations.

Amino Acid Sequence↗
PubMed2006

Cross-talk with myeloid accessory cells regulates human natural killer cell interferon-gamma responses to malaria.

Data from a variety of experimental models suggest that natural killer (NK) cells require signals from accessory cells in order to respond optimally to pathogens, but the precise identity of the cells able to provide such signals depends upon the nature of the infectious organism. Here we show that the ability of human NK cells to produce interferon-gamma in response to stimulation by Plasmodium falciparum-infected red blood cells (iRBCs) is strictly dependent upon multiple, contact-dependent and cytokine-mediated signals derived from both monocytes and myeloid dendritic cells (mDCs). Contrary to some previous reports, we find that both monocytes and mDCs express an activated phenotype following short-term incubation with iRBCs and secrete pro-inflammatory cytokines. The magnitude of the NK cell response (and of the KIR(-) CD56(bright) NK cell population in particular) is tightly correlated with resting levels of accessory cell maturation, indicating that heterogeneity of the NK response to malaria is a reflection of deep-rooted heterogeneity in the human innate immune system. Moreover, we show that NK cells are required to maintain the maturation status of resting mDCs and monocytes, providing additional evidence for reciprocal regulation of NK cells and accessory cells. However, NK cell-derived signals are not required for activation of accessory cells by either iRBCs or bacterial lipolysaccharide. Together, these data suggest that there may be differences in the sequence of events required for activation of NK cells by non-viral pathogens compared to the classical model of NK activation by virus-infected or major histocompatibility complex-deficient cells. These findings have far-reaching implications for the study of immunity to infection in human populations.

Animals↗
PubMed2005

Administration of yeast glucan enhances survival and some non-specific and specific immune parameters in carp (Cyprinus carpio) infected with Aeromonas hydrophila.

Effects of beta-glucan administration on survival and immune modulations were studied in Cyprinus carpio against the bacterial pathogen, Aeromonas hydrophila. Beta-glucan was extracted from Saccharomyces cervisiae and purified. A virulent strain of the pathogen A. hydrophila was collected from infected fish. Different concentrations of beta-glucan were administered to test animals on day 1, 3 and 5 through different routes (intraperitoneal injection (ip), bathing and oral administration). Control and test animals were challenged by ip injection of LD50 concentration of A. hydrophila on day 7 and mortality was observed and Relative Percent Survival (RPS) was calculated. Intraperitoneal injection of 500 microg of glucan significantly enhanced the RPS; bathing and oral administration of glucan did not influence the RPS. On day 7, test animals injected with 100, 500 and 1000 microg of glucan had a significant increase in total blood leucocyte counts and an increase in the proportion of neutrophils and monocytes. Superoxide anion production by kidney macrophages was also elevated. RT-PCR and northern blot analysis of interleukin-1 mRNA showed elevated expression in kidney on day 7 in fish injected with glucan. Glucan had an adjuvant effect on antibody production as pretreatment by injection of 100-1000 microg glucan/fish resulted in the highest antibody titer against A. hydrophila following vaccination. Classical and alternative complement pathways were not affected by glucan administration by any of the three routes.

Aeromonas hydrophila↗
PubMed2005

Role of aldosterone in diabetic nephropathy.

In the last 10 years, many studies have focused on the non-classical action of aldosterone. One of the most important new aspects of aldosterone is its pathogenic role as proinflammatory and profibrotic molecules. It has been reported that aldosterone induces myocardial fibrosis and vascular inflammation through up-regulation of various proinflammatory and profibrotic cytokines. We investigated the effect of aldosterone and spironolactone, which is a non-selective mineralocorticoid receptor antagonist, on monocyte chemoattractant peptide (MCP-1) and collagen synthesis in cultured mesangial and tubular epithelial cells. In addition, to evaluate the effect of spironolactone on diabetic nephropathy, we used Otsuka Long-Evans Tokushima Fatty (OLETF) rats which are known type 2 diabetic animal models. Spironolactone treatment did not induce any significant change in blood glucose levels and blood pressure. However, spironolactone therapy significantly inhibited urinary albumin and MCP-1 excretion. Spironolactone treatment also suppressed renal mRNA expression for MCP-1, macrophage migration inhibitory factor (MIF) as well as intrarenal protein synthesis for ED-1 and MIF. Morphologically, spironolactone treatment significantly prevented glomerulosclerosis, collagen deposition and connective tissue growth factor (CTGF) expression in diabetic rats. In cultured cell experiments, aldosterone directly increased the MCP-1, collagen secretion and spironolactone treatment abolished aldosterone-induced MCP-1 and collagen synthesis. Surprisingly, aldosterone treatment did not induce any significant change in TGFbeta1 gene transcription. Finally, we found that NF-kB activity was increased after stimulation with aldosterone and spironolactone therapy inhibited their activation. In addition, prior treatment with pyrrolidine dithiocarbamate (PDTC), which is a NF-KB inhibitor, inhibited aldosterone-induced MCP-1 protein secretion. These results suggest that aldosterone blockade could play a role in preventing the progression of diabetic nephropathy via anti-inflammatory and antifibrotic mechanisms.

Albuminuria↗
PubMed1998

Cellular activity of murine phagocytes isolated from peripheral blood by a discontinuous gradient.

A mixture of Ficoll 400 and sodium diatrizoate (Hypaque) at a density of 1.077 g/ml has been used to isolate the mononuclear cells from the remaining haematic cells. A simple, inexpensive and classical method was established to obtain substantially erythrocyte-free polymorphonuclear cell preparations from mouse peripheral blood, using a mixture of the same substances but at a density of 1.119 g/ml. This method along with that at a density of 1.077 g/ml allows two cellular bands to appear which contain mononuclear and polymorphonuclear (PMN) cells, respectively. Using this method, the counts of monocytes isolated from peripheral blood are significantly greater than those obtained by a one-step Ficoll-Hypaque procedure. On the contrary, the counts of PMN cells are significantly smaller than when sedimentation in dextran (6% solution) is used after gradient centrifugation. In this paper, chemiluminescence assay has been used to analyze the possible variations in phagocytic activity of cells isolated by both procedures, since it appears to be one of the most sensitive methods available for this purpose. The results obtained show a slightly greater activation in monocytes and PMN cells isolated by one-step Ficoll-Hypaque procedure, in comparison with another method which uses both Ficoll-Hypaque 1077 and Ficoll-Hypaque 1119, although statistical differences were not significant.

Animals↗
PubMed2005

Differential capability for phagocytosis of apoptotic and necrotic leukemia cells by human peripheral blood dendritic cell subsets.

CD11c+ dendritic cells (DC) and plasmacytoid DC (PDC) are the two major DC subsets in human peripheral blood. For the purpose of immunotherapy with DC, it is important to investigate the phagocytosis of killed tumor cells by different DC subsets. Using immature monocyte-derived DC (iMoDC) as reference, we have compared the ability of CD11c+ DC and PDC to phagocytose apoptotic and necrotic K562 leukemia cells. Freshly isolated CD11c+ DC phagocytosed apoptotic and necrotic K562 cells, whereas PDC did not show any evidence of uptake of dead cells. Blocking studies showed that CD36 is importantly involved in uptake of apoptotic and necrotic material. CD91 and CD11c were also involved. In addition, we found that beta5 integrin was expressed on CD11c+ DC but not in its classical association with alphaV. Uptake of apoptotic K562 cells by CD11c+ DC was increased following incubation with granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-4, alone or in combination with transforming growth factor-beta1, to levels comparable with those observed for iMoDC. Phagocytosis of dead cellular material by the GM-CSF/IL-4-treated CD11c+ DC was largely restricted to a subset expressing low levels of human leukocyte antigen-DR and CD83. Thus, the relationship between phagocytosis of antigenic material and expression of maturation-related cell-surface molecules is similar for CD11c+ DC and MoDC. We conclude that CD11c+ DC in peripheral blood are precursor cells, which under the influence of cytokines, differentiate to cells with DC phenotype and function.

Apoptosis↗