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The article presents a list of forthcoming papers related to immunology. Some of the papers include "Inhibitory p41 Isoform of Invariant Chain and Its Potential Target Enzymes Cathepsins L and H in Distinct Populations of Macrophages in Human Lymph Nodes," by V. Zavašnik-Bergant, A. Schweiger, T. Bevec, R. Golouh, V. Turk, J. Kos, and " Echinococcus Multilocularis Proliferation in Mice and Respective Parasite 14-3-3 Gene Expression is Mainly Controlled by an CD4 + T cell Mediated Immune Response," by W. Dei, A. Waidvogel, M. Siles-Lucas, Bruno Gottistein.

Diabetes mellitus (DM) is a metabolic inflammatory disease with a high incidence worldwide. Patients with DM are at a high risk for all types of infections. Type 1 DM is characterised with immune destruction of pancreatic β cells, while type 2 diabetes is characterised with insulin resistance and β cell dysfunction, both of which result in disorders of glucose and lipid metabolism. This metabolic disorder causes functional defects of immune cells, aberrant production of inflammatory cytokines, dysregulated immune responses, advanced pathophysiological injury of the body, and increased mortality in populations with DM upon infections. Starting with the change of natural immune system in patients with DM, this paper focused on the enhanced severity of infections in DM and the underlying innate immune alterations in preclinical and clinical studies, aiming to better understand the influence of DM on the susceptibility, pathophysiology, and clinical outcomes in infections. [ABSTRACT FROM AUTHOR]

It is known that two major cytotoxins, lymphotoxin (LT) and tumour necrosis factor (TNF), are produced by T cells and macrophages, respectively. We report in this paper that a human T-cell hybridoma, AC5-8, produces TNF in addition to LT depending on the kind of stimuli used. When phorbol myristate acetate (PMA) and concanavalin A (Con A) or PMA alone were used to induce AC 5-8 cells to secrete a cytotoxin, we found that the cytotoxin secreted was antigenically indistinguishable from LT. On the other hand, when AC5-8 cells were activated by PMA and A23 187, they secreted another cytotoxin which was antigenically indistinguishable from TNF, in addition to LT. These two cytotoxins could be separated by affinity chromatography on a column of Con A-Sepharose. A cytotoxin, which did not bind to the Con A-Sepharose column and showed about 70- 95% of the total cytotoxic activity secreted from AC5-8 cells stimulated with PMA and A23 187, was found to be antigenically identical to TNK. The other cytotoxin, which bound to the Con A-Sepharose column and showed only 5 - 30% of the total activity induced by PMA and A23 187, was found to be antigenically identical to LT. [ABSTRACT FROM AUTHOR]

In a previous paper, we have described a cell-surface associated adhesive glycoprotein (AF) that has been separated and highly purified from rat ascites hepatoma AH136B cells. AF was found to induce the aggregation and adhesiveness of hepatoma cells. AF was also shown to have a mitogenic activity on rat T lymphocytes, and to stimulate them to produce a lymphokine chemotactic for macrophages. In the present paper, we have examined the effects of AF on natural killing (NK) activity by rat spleen cells against NK-sensitive YAC-1 cells using 51Cr-release cytotoxicity assay. NK activity of spleen cells was potentiated by AF treatment in a dose-dependent manner. A short incubation with AF was sufficient for the potentiation of NK activity, whereas the potentiation by OK-432, which is well known as a potentiator of anti-tumour activity, required a longer stimulation. Macrophage depletion from spleen cells resulted in the decreased potentiating effects of OK-432, whereas the depletion failed to influence the effects of AF. In subsequent experiments, it was found that AF could potentiate NK activity of the NK-cell enriched fraction. We further found that culture supernatants from spleen cells and peritoneal exudate cells treated with OK-432 potentiate the NK activity, whereas those from AF-treated cells fail. It was thus suggested that AF acts directly on the cells responsible for NK activity, and that the mechanisms of AF-induced potentiation of NK activity differ from those of OK-432-induced potentiation. [ABSTRACT FROM AUTHOR]

Removal of apoptotic cells from inflammatory sites by macrophages is an important step in the resolution of inflammation. However, the effect of inflammatory modulators on phagocytic clearance of apoptotic cells remains to be clarified. In this paper, we demonstrate that lipopolysaccharide (LPS), a potent inflammatory agent, inhibits the phagocytosis of apoptotic neutrophils by mouse peritoneal macrophages. This inhibition can be attributed to both LPS-mediated induction of tumour necrosis factor (TNF-α) and suppression of growth arrest-specific gene 6 (Gas6) in macrophages. We found that LPS-induced TNF-α production inhibited phagocytic ability of macrophages in an autocrine manner. In contrast, Gas6 expression in macrophages was blocked by LPS, which also contributes to the inhibition of macrophage phagocytosis by LPS. Our data suggest that phagocytic clearance of apoptotic neutrophils by macrophages can be regulated by local pro- and anti-inflammatory factors in two opposite states. [ABSTRACT FROM AUTHOR]

Mannose-binding lectin (MBL) exists in the serum as a complex with MBL-associated serine protease (MASP). A recent paper described how MASP-free recombinant rat MBL stimulates the phagocytosis of Escherichia coli and Staphylococcus aureus by rat Kupffer cells through an increase in the level of a phagocytosis receptor. We have examined the effect of human MBL on the phagocytic action of human macrophages. Purified recombinant human MBL stimulated the phagocytosis of E. coli by THP-1 macrophages, leaving that of latex beads, apoptotic human cells, zymosan particles or S. aureus unchanged. This stimulatory effect was observed when either phagocytes or targets were preincubated with MBL. Furthermore, MBL bound to THP-1 macrophages as well as to E. coli, but not to S. aureus, through lipid A. These results indicated that human MBL in the absence of MASP stimulates macrophage phagocytosis of E. coli by bridging targets and phagocytes. [ABSTRACT FROM AUTHOR]

The mechanisms which generate heterogeneity amongst resident tissue macrophages (Mø) are poorly understood. In a previous study we described a novel mouse Mø haemagglutinin, which binds unopsonized sheep erythrocytes. This sheep erythrocyte receptor (SER) is expressed at high levels on stromal Mø from bone marrow and lymph nodes, but at low levels on Mø from serous cavities and broncho-alveolar spaces. In this paper we demonstrate that a species-restricted factor in mouse serum is required in vitro for optimal maintenance of SER on resident bone marrow Mø and for its induction on Mø populations which normally lack this receptor. Using thioglycollate-elicited peritoneal Mø, induction of SER by mouse serum was doses dependent, reached maximal levels by 3- 4 days, required the continuous presence of mouse serum, and was fully reversible. Reexpression following trypsinization was inhibited by cycloheximide, showing that protein synthesis by Mø was necessary. Using a quantitative microtitre plate assay to measure levels of the inducing activity (SER-IA) in different samples, it was found to be heatelabile, non-dialysable, precipitable by polyethylene glycol and inactivated at pH 4 but not at pH 96. On gel filtration of mouse serum, a single major peak of activity was obtained with an apparent MW of around 70,000. SER-IA appears to be unrelated to a variety of factors and cytokines which affect Mø function, including colony-stimulating factors I (CSF-1). The possible role of SER-IA in regulating the differential expression of SER in vivo is discussed. [ABSTRACT FROM AUTHOR]

Pretreatment of EL4 cells with 12-O-tetradecanoyl phorbol- 13-acetate (TPA) for 30 mm renders them resistant to lysis by activated macrophages (Mø). This resistance was augmented two to three-fold when TPA-trated EL4 cells were incubated for 2-6 hr prior to co-culture with Mø. Preincubation of TPA-treated cells for 24 hr could result in 100% resistance. In this paper we show that an endogenous ligand for protein kinase C, oleolyl-2-acetate glycerol (OAG), was capable of inducing tumour cell resistance to Mø kill and, similar to the effects seen with TPA, OAG did not affect the selective binding of tumour cells to activated Mø. Another important observation on the mechanism of TPA induction of tumour cell resistance was that once the target cells were progranuned to die after a minimal contact with activated Mø of 4-6 hr, TPA treatment was ineffective in altering the percent lysis 20 hr later. To investigate whether any possible correlation exists between TPA-induced protein phosphorylation and acquisition of resistance, EL4 cells were labelled with 32P and treated simultaneously with TPA, and cellular proteins were resolved by two adimensional gel electrophoresis. Eight polypeptides (MW 24,000-70,000, p1 48-61) showed consistent increased phosphorylation as a result of WA treatment. One-minute exposure with TPA resulted in enhanced phosphorylation of only four peptides (MW 39,000, 58,000, 63,000, 70,000) while all eight polypeptides showed increased phosphorylation by 10 mm. [ABSTRACT FROM AUTHOR]

The expression of a diverse array of receptors for sulphated polysaccharides on lymphocytes has been demonstrated by Parish & Snowden (1985). This paper presents evidence to suggest that other cell types, namely macrophages, polymorphonuclear leucocytes, mast cells and fibroblasts, can bind similar polysaccharides. Using a rosetting assay and eleven structurally unique polysaccharides, each cell type was observed to bind a characteristic array of these polysaccharides. Analysis of the polysaccharide reactivity of macrophages revealed that BCG-activated and thioglycollate-elicited macrophages express an expanded repertoire of reactivity compared to resident peritoneal macrophages. For example, only thioglycollate-elicited macrophages, but not resident and BCG-activated peritoneal macrophages, reacted with the glycosaminoglycans, chondroitin-4-sulphate, chondroitin-6-sulphate and dermatan sulphate, while both BCG- and thioglycolate-activated, but not resident peritoneal macrophages, bound pentosan polysulphate-coupled sheep erythrocytes. The expression of the receptors for chondroitin-4- and -6-sulphate was observed to be cyclic and peaked at 2 and 5-6 days after thioglycollate treatment. Preliminary analyses of the functional significance of the observed binding of polysaccharides to macrophages revealed that heparin, fucoidan and kappa-carrageenen were specifically endocytosed. However, endocytosis of all other test polysaccharides was not observed. Finally, polysaccharide-coupled sheep erythrocytes were not phagocytosed, even though they interacted strongly with the macrophage surface. The possible relevance of these observations to an inflammatory response and as a means of identifying cellular subsets is discussed. [ABSTRACT FROM AUTHOR]

In this paper we describe production of alloantisera specific for determinants encoded by I-J gene loci expressed on macrophages. B10.A(3R) (l-Jb) mice were hyperimmunized with pure populations of macrophages grown in vitro from bone marrow stem cells of congenic B10.A(5R) mice. The antisera contained predominantly IgM antibody that was non-adherent to protein-A-Sepharose with a minor component of IgGI, and IgG2a antibodies that were adherent to protein.A-Sepharose. The protein- A non-adherent antibody completely blocked the in vitro generation of humoral immune responses to sheep erythrocytes by spleen cell from B10.A(5R) mice and from inbred strains that share the I-Jk haplotypes, but did not alter the responses of spleen cells of the I-Jb haplotype. In the presence of complement. both protein-A adherent and protein-A non-adherent antibodies eliminated the capacity of B10.A(5R) spleen cells to generate humoral and proliferative responses, but the functional activity of B10.A(3R) cells was unaffected. These data indicate the I-Jk specificity of the antisera. The capacity of the anti-macrophage antibody to block humoral immune induction was removed by absorption with bone marrow-derived macrophages from B10.A(5R) mice, but not from B10.A(3R) mice. Further, the B10.A(5R) macrophages completely restored the humoral responses of antibody- and complement-treated B10.A(5R) spleen cells, but B10.A(3R) macrophages showed only partial restoration that was consistent with a factor-mediated allogeneic effect. These data demonstrate the specificity of our anti-I-J sera for macrophages and indicate that bone marrow-derived macrophages express surface I-J encoded molecules. [ABSTRACT FROM AUTHOR]

The experiments described in this paper were designed to determine the degradation of soluble IgG aggregates (AIgG) bearing C3b by guinea-pig peritoneal macrophages with different numbers of functional C3b receptors. The number of functional Fc receptors for AIgG containing 40 molecules of IgG per aggregate (AIgG40) were kept constant during these experiments. By increasing the concentration of trypsin for the treatment of normal peritoneal macrophages a dose-dependent inactivation of C3b receptors was achieved as determined by the binding of tetrameric [125I]-C3b([125I]-AC3b). Normal peritoneal macrophages bound 148,500 AIgG40 and 60,300 AC3b per cell. Treatment of the macrophages for 15 rain at 37° with incremental amounts of trypsin from 60 to 1000 µg/ml did not affect the binding of AIgG40 to macrophages but caused a dose-related loss of up to 95% of AC3b binding, indicating functional inactivation of C3b receptors. Degradation of trichloroacetic acid non-precipitable protein of [125I]-AIgG40 by 106 macrophages was 38±6% in medium alone and 60 ±8% in the presence of 10% fresh guinea-pig serum (NGPS) after 60 rain at 37°. The inactivation of 25%, 50%, 72% and 94% of C3b receptors by trypsin did not affect the degradation of AIgG40 in medium alone, but decreased degradation from 69% to 58%, 47%, 32% and 13% of AIgG40 respectively, in the presence of 10% GPS. Macrophages (106) in medium alone degraded 40%, 47%, 65% and 68% of AIgG40 beating 0, 5, 10, 16 and 20 C3b molecules per aggregate, indicating a dose-dependent enhancement of degradation by bound C3b; conversely, inactivation of 95% of C3 receptor on the macrophages resulted in 39%, 30%, 12%, 5% and 6% degradation of these AIgG40-C3b, indicating a dose-related inhibition by aggregate-bound C3b in the absence of cellular C3 receptor. These experiments stress the importance of Fc and C3b receptor co-operation and immune complex bound C3b. [ABSTRACT FROM AUTHOR]

Murine lymphocytes spontaneously bind autologous and allogeneic erythrocytes via receptors that primarily recognize self H-2L molecules on the erythrocyte surface. Normal mouse serum contains a factor, termed autorosette inhibition factor (AIF), that very effectively blocks autorosette formation. This paper describes experiments that determine the origin and nature of serum AIF. It was found that AIF lacks strain and species , serum from several mammalian and nonmammalian species inhibiting the autorosetting of BALB/c thymocytes. However, mouse strains differed in the levels of AIF in their serum. Furthermore, AIF appears to directly interact with autorosetting roceptors on lymphocytes as thymocytes from the BALB/c-H-2dm2 mutant strain, which lack autorosetting receptors, were unable to absorb the factor. Several lines of experimental evidence indicated that AIF is secreted by a population of short-lived, radiosensitive macrophages (or monocytes). Firstly, in vivo administration of the anti-macrophage agents carrageenan and silica profoundly depressed AIF levels in serum. Secondly, in vitro culturing of different lymphoid cells revealed that AIF is secreted by an adherent population of peritoneal cells. Thirdly, total body irradiation experiments demonstrated that AIF production is dependent upon a radiosensitive cell that is bone marrow derived. Finally, AIF was purified to homogeneity from mouse plasma and shown to be a single polypeptide chain with a molecular weight of 84,000. [ABSTRACT FROM AUTHOR]

Results of in vivo and in vitro experiments suggest that the early suppression of brucella growth in double stranded polyadenylic-polyuridylic acid(poly A: U-) treated mice was due to a non-specific activation of macrophages by poly A: U. Poly A: U administered intraperitoneally at the time of brucella infection failed to enhance T-cell mediated responses to the organism, namely delayed-type hypersensitivity to brucellin and adoptive transfer of immunity to the infection. Poly A: U did not augment the protective antibodies formed in response to infection. Although poly A:U has been previously found to suppress brucellosis in athymic (nude) mice, it did not enhance the thymus-dependent antibody response to sheep erythrocytes in brucella-infected nudes, suggesting that it did not significantly enhance maturation of their helper T-cell percursors. Increased macrophage spreading, an indication of activation, was seen immediately after administration of poly A: U and Brucella abortus. Later on the infection spreading was suppressed, a phenomenon which appears to relate to the biphasic effect of poly A: U in vivo described in the accompanying paper. Peritoneal macrophages treated in vitro with poly A: U were stimulated to spread on plastic surfaces, even when T lymphocytes were removed with anti-Thy-1 serum and complement. [ABSTRACT FROM AUTHOR]

Lymph node and spleen cells from normal mice were cultured for 3 days with polyoma virus-induced tumour, Ehrlich's ascites turnout or leukaemia L 1210 cells. This resulted in in vitro immunization of the lymphocytes, which were then transferred to irradiated target cells labelled with 51Cr. Normal, i.e. non-immune thioglycollate-stimulated peritoneal macrophages were also added to some tubes. Non-immune macrophages mixed with immunized lymphocytes showed a significantly increased ability to destroy tumour ceils as compared with macrophages in the absence of immunized lymphocytes. The immunized lymphocytes were almost entirely inactive alone. When the number of macrophages was kept constant the cytotoxicity was dependent on the number of viable immunized lymphocytes placed on the target cells. Immunized lymphocytes, in the presence of macrophages, only exhibited strong killing of the target cells against which they had been immunized; some lysis of ‘bystander’ cells was, however, seen provided specific target cells were present. Macrophage monolayers exposed to immunized lymphocytes upon contact with specific antigen became ‘armed’ and showed a significant cytotoxicity for specific target cells. When immunized lymphocytes and normal macrophages were treated with actinomycin D and puromycin, cytotoxicity was inhibited in the immunized lymphocytes but not in the macrophages. The possible mechanism of normal macrophage cooperation with immunized lymphocytes in the cytotoxic killing reaction is discussed. Results presented in this paper favour the view that immunologically specific cytophilic factor (presumptive cytophilic antibody) is involved in the macrophage-mediated cytotoxicity in the system studied. [ABSTRACT FROM AUTHOR]

We have previously reported an experimental autoimmune model induced by the local infection of Listeria monocytogenes. The unilateral inoculation of virulent Listeria into a testis of a normal mouse induced a delayed-type hypersensitivity response against testicular antigen and caused autoimmune orchitis in the contralateral testis. The orchitis was transferred to naive mice by T cells from the intratesticularly infected mice. In this paper, we demonstrated that avirulent Listeria, which lacks the expression of listeriolysin O, failed to induce any anti-testicular responses or contralateral orchitis even when it was inoculated at a high dose into the testis. Furthermore, the intraperitoneal inoculation of virulent Listeria with testicular antigen induced the antitesticular responses and orchitis although intraperitoneal inoculation of testicular antigen with avitulent Listeria failed to induce them. The difference between virulent and avirulent Listeria in the induction of anti-testicular responses was supposed to be dependent on the difference in macrophage activation by the two bacterial strains because, first, the anti-testicular responses were elicited in normal mice when macrophages from virulent Listeria-infected mice were intraperitoneally transferred with testicular antigen although no viable bacteria were detected from the macrophages, and secondly, in contrast, the intraperitoneal co-inoculation of macrophages from avirulent Listeria-infected mice and testicular antigen failed to elicit any antitesticular responses. Finally, we found that the virulent Listeria-induced macrophages expressed a higher level of CD80 (BT-1) and CD86 (B7-2) molecules than did the avirulent Listeria-induced macrophages and naive peritoneal macrophages. These results thus suggest that virulent Listeria activates macrophages to induce autoreactive T cells while avirulent Listeria does not. The up-regulation of B7 molecules by virulent Listeria infection is a candidate of the mechanism for the activation of autoreactive T cells. [ABSTRACT FROM AUTHOR]

Invariant chain (Ii) plays an important role in major histocompatibility complex (MHC) class II antigen processing and presentation and is constitutively synthesized in B lymphocytes, in macrophages, dendritic cells and in some epithelial cells. It has been shown that interferon-γ, tumour necrosis factor-α and interleukin-4 co-regulate Ii and MHC class II expression in various cell types. We describe here a novel regulation of Ii expression in macrophages. Treatment of the premature monocytic cell lines WEHI 265.1, M1 and WEHI-3B with recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) strongly enhances Ii expression while class II expression is not induced. In contrast, GM-CSF did not enhance Ii in mature macrophage cell lines. The increase of Ii expression m WEHI 265.1 cella takes several days. This long induction time, and a difference in activity between GM-CSF-conditioned medium and GM-CSF, together suggest that GM-CSF stimulates WEHI 265.1 cells to secrete a factor that modulates Ii expression. These results may imply a class II-independent function of Ii, which we discuss in this paper. [ABSTRACT FROM AUTHOR]

Peripheral lung tissue contains large numbers of T cells, strategically located for immune surveillance at the blood-air interface. Given the intensity of antigenic exposure at this site, it is clear that local T-cell activation events require strict control, in order to maintain tissue homeostasis. How this control is achieved in this unique tissue microenvironment is unknown, and the present study sought to elucidate the process via detailed analysis of the surface phenotypic characteristics of freshly isolated lung T cells. We report below that these cells display typical characteristic of ‘postactivation’, notably elevated basal Ca2+ concentrations, down-modulated T-cell receptors, expression of Ia and ‘late’ activation antigens and concomitant CD4/CD8. However, levels of interleukin-2 receptor and CD2 expression were below those expected of ‘activated’ T-cell populations, and virtually all of the cells were found to be in the G0/G1 phases of the cell cycle. These properties bear a remarkable similarity to those of T cells activated in the presence of endogenous tissue (alveolar) macrophages from the lung (see accompanying paper). We hypothesize that they reflect the in vivo operation of an endogenous macrophage-mediated T-cell anergy-induction process, the function of which is to limit the local clonal expansion of T cells in peripheral lung tissue after in situ activation. [ABSTRACT FROM AUTHOR]

Alveolar macrophages (AM) are recognized as archetypal ‘activated’ macrophages with respect to their capacity to suppress T-cell responses to antigen or mitogen, and this function has been ascribed an important role in the maintenance of local immunological homeostasis at the delicate blood: air interface. The present study demonstrates that this suppression involves a unique form of T-cell anergy, in which ‘AM-suppressed’ T cells proceed normally through virtually all phases of the activation sequence including Ca2+ flux, T-cell receptor (TCR) modulation, cytokine [including interleukin-2 (IL-2)] secretion and IL-2 receptor (IL-2R) expression. However, the ‘suppressed’ T cells fail to up-regulate CD2, and do not re-express normal levels of TCR-associated molecules after initial down-modulation; moreover, they are unable to transduce IL-2 signals leading to phosphorylation of IL-2R-associated proteins, and remained locked in G0/G1. The induction of this form of anergy is blocked by an NO-synthase inhibitor, and is reversible upon removal of AM from the T cells, which then proliferate in the absence of further stimulation. We hypothesize that this mechanism provides the means to limit the magnitude of local immune responses in this fragile tissue microenvironment, while preserving the capacity for generation of immunological memory against locally encountered antigens via clonal expansion of activated T cells after their subsequent migration to regional lymphoid organs. In an accompanying paper, we demonstrate that a significant proportion of T cells freshly isolated from lung exhibit a comparable surface phenotype. [ABSTRACT FROM AUTHOR]

Liposomes containing the drug dichloromethylene diphosphonate (Cl2MDP) can eliminate phagocytic cells, such as macrophages, when injected in vivo. In this paper we report that Cl2MDP-containing liposomes have been used experimentally to determine the extent to which cutaneous macrophages participate (1) in the induction of contact hypersensitivity (CH) when hapten is painted on normal murine skin, and (2) in the induction of CH or tolerance when hapten is painted on murine skin that has been exposed to ultraviolet B (UVB) radiation. Intradermal (i.d.) injections of Cl2MDP-containing liposomes were found to have no deleterious effects on CH induction via normal skin, whether the amount of hapten (dinitrofluorobenzene) applied to the cutaneous surface was optimal or excessive. Moreover, Cl2MDP-containing liposomes did not deplete the epidermis of Langerhans' cells. However, similar i.d. injections of Cl2MDP-containing liposomes did prevent the induction of CH when hapten was painted on UVB-irradiated skin of BALB/c mice, a strain that develops CH when hapten is applied to UVB-exposed skin. These findings indicate that the antigen-presenting cell (APC) function found in skin of UVB-resistant mice following exposure to UVB radiation can be attributed to macrophages. This explains why these mice develop and display CH after UVB radiation. By contrast, i.d. injections of Cl2MDP-containing liposomes failed to prevent the induction of the tolerance when hapten was applied to the surface of UVB-exposed skin of UVB-susceptible mice, such as C57BL/6. Since the dermis of UVB-exposed skin of these mice is known to contain a novel population of cells that can provide a tolerance-conferring signal, the current findings rule out macrophages as the responsible cell type. [ABSTRACT FROM AUTHOR]

This paper describes the ultrastructural location of labelled antigens and carbon in the spleens of rats from 4 minutes to 5 days after injection. Particular attention was focused on the sites of deposition 4 minutes after intra-arterial injection of microgram quantities of 125I-labelled Salmonella flagellar antigens, crayfish haemocyanin and BSA, using colloidal carbon for comparison. The combination of radioautography with both light and electron microscopy showed the importance of antigen binding by lymphocytes in the marginal zone of the spleen. Macrophage sequestration of antigens was not prominent in the spleen, although it occurred in the liver with the flagellar antigens and haemocyanin. In the spleen marginal zone, avid antigen-binding cells were found in situ 4 minutes after the injection of labelled haemocyanin. These appear to be the counterpart in vivo of antigen-binding lymphocytes prepared in vitro. Such cells also occurred infrequently after the injection of labelled polymerized flagellin, but were not found with either BSA or carbon. The apparent movement of flagellar antigen from the marginal zone to the white pulp between 1 and 2 hours after injection was seen to involve lymphocyte-associated antigen. The follicular antigen localization occurring from 1 day onwards after injection was on the dendritic reticular cells of germinal centres, as has been described in lymph nodes after subcutaneous injection. Carbon particles were rapidly sequestered in macrophages of the spleen and liver, although some particles were found between cells in the marginal zone for as long as 2 hours after injection. By 2 and 5 days, however, all the carbon was in phagocytes, even in the white pulp. Differences between the localization of antigens and carbon were clear, even in the ultrastructural sites of their location in tingible body macrophages of germinal centres. The unexpected emphasis of lymphocyte association with labelled antigens in the spleen marginal zone has allowed a revision of the mechanism previously proposed for the movement of antigens within the microenvironments of the spleen. [ABSTRACT FROM AUTHOR]

Exosomes are extracellular vesicles released by all cell types; perform several important functions such as cell‐to‐cell communication, growth, differentiation and so on. Exosomes elicit several signalling mechanisms as they carry information in the form of DNA, RNA or protein docked on them. We show that exosomes released from Mycobacterium tuberculosis (Mtb)‐infected macrophages not only induce differentiation of naïve monocytes but also generate functionally active macrophages via MAPK‐dependent signalling mechanism through MK‐2 and NF‐κβ activation which is completely different from the differentiation induced by exosomes from uninfected macrophages. Further, we elucidate unequivocally the signalling mechanism behind the enhanced release of exosome generation from infected macrophages driven by AKT phosphorylation involving Rab7a and Rab11a. Genes of both ESCRT‐dependent and ‐independent pathways are found to be involved in enhanced exosomes release and are modulated by AKT. However, interestingly, the genes of the ESCRT‐independent pathway are dependent on NF‐κβ activation while the genes of the dependent pathway are not, suggesting two parallel signalling cascades operating in tandem. [ABSTRACT FROM AUTHOR]

Published data for the Streptococcus pneumoniae virulence factor Pneumolysin (Ply) show contradictory effects on the host inflammatory response to infection. Ply has been shown to activate the inflammasome, but also can bind to MRC‐1 resulting in suppression of dendritic cell inflammatory responses. We have used an in vitro infection model of human monocyte‐derived macrophages (MDM), and a mouse model of pneumonia to clarify whether pro‐ or anti‐inflammatory effects dominate the effects of Ply on the initial macrophage inflammatory response to S. pneumoniae, and the consequences during early lung infection. We found that infection with S. pneumoniae expressing Ply suppressed tumour necrosis factor (TNF) and interleukin‐6 production by MDMs compared to cells infected with ply‐deficient S. pneumoniae. This effect was independent of bacterial effects on cell death. Transcriptional analysis demonstrated S. pneumoniae expressing Ply caused a qualitatively similar but quantitatively lower MDM transcriptional response to S. pneumoniae compared to ply‐deficient S. pneumoniae, with reduced expression of TNF and type I IFN inducible genes. Reduction of the MDM inflammatory response was prevented by inhibition of SOCS1. In the early lung infection mouse model, the TNF response to ply‐deficient S. pneumoniae was enhanced and bacterial clearance increased compared to infection with wild‐type S. pneumoniae. Overall, these data show Ply inhibits the initial macrophage inflammatory response to S. pneumoniae, probably mediated through SOCS1, and this was associated with improved immune evasion during early lung infection. [ABSTRACT FROM AUTHOR]

Trained immunity (TRAIM) may be defined as a form of memory where innate immune cells such as monocytes, macrophages, dendritic and natural killer (NK) cells undergo an epigenetic reprogramming that enhances their primary defensive capabilities. Cross‐pathogen protective TRAIM can be triggered in different hosts by exposure to live microbes or microbe‐derived products such as heat‐inactivated Mycobacterium bovis or with the glycan α‐Gal to elicit protective responses against several pathogens. We review the TRAIM paradigm using two models representing distinct scales of immune sensitization: the whole bacterial cell and one of its building blocks, the polysaccharides or glycans. Observations point out to macrophage lytic capabilities and cytokine regulation as two key components in non‐specific innate immune responses against infections. The study of the TRAIM response deserves attention to better characterize the evolution of host–pathogen cooperation both for identifying the aetiology of some diseases and for finding new therapeutic strategies. In this field, the zebrafish provides a convenient and complete biological system that could help to deepen in the knowledge of TRAIM‐mediated mechanisms in pathogen–host interactions. [ABSTRACT FROM AUTHOR]

The NLRP3 inflammasome is a multiprotein complex that regulates caspase‐1 activation and subsequent interleukin (IL)‐1β and IL‐18 release from innate immune cells in response to infection or injury. Derivatives of the metabolites itaconate and fumarate, dimethyl itaconate (DMI), 4‐octyl itaconate (4OI) and dimethyl fumarate (DMF) limit both expression and release of IL‐1β following NLRP3 inflammasome activation. However, the direct effects of these metabolite derivatives on NLRP3 inflammasome responses require further investigation. Using murine bone marrow‐derived macrophages, mixed glia and organotypic hippocampal slice cultures (OHSCs), we demonstrate that DMI, 4OI and DMF pretreatments inhibit pro‐inflammatory cytokine production in response to lipopolysaccharide (LPS), as well as inhibit subsequent NLRP3 inflammasome activation induced by nigericin. DMI, 4OI, DMF and monomethyl fumarate (MMF), another fumarate derivative, also directly inhibited biochemical markers of NLRP3 activation in LPS‐primed macrophages, mixed glia, OHSCs and human macrophages in response to nigericin and imiquimod, including ASC speck formation, caspase‐1 activation, gasdermin D cleavage and IL‐1β release. DMF, an approved treatment of multiple sclerosis, as well as DMI, 4OI and MMF, inhibited NLRP3 activation in macrophages in response to lysophosphatidylcholine, which is used to induce demyelination, suggesting a possible mechanism for DMF in multiple sclerosis through NLRP3 inhibition. The derivatives also reduced pro‐IL‐1α cleavage in response to the calcium ionophore ionomycin. Together, these findings reveal the immunometabolic regulation of both the priming and activation steps of NLRP3 activation in macrophages. Furthermore, we highlight itaconate and fumarate derivatives as potential therapeutic options in NLRP3‐ and IL‐1α‐driven diseases, including in the brain. [ABSTRACT FROM AUTHOR]

Retinal neovascularization (RNV), a pathological process shared among diabetic retinopathy, retinopathy of prematurity and other retinopathies, has been widely studied, but the mechanism remains unclear. In this study, the mechanism by which the interleukin (IL)‐23/IL‐17 axis regulates RNV in oxygen‐induced retinopathy (OIR) model mice and in cell experiments in vitro was characterized. In the retinas of OIR mice, IL‐23/IL‐17 axis activation was increased and regulated RNV formation, and this effect was accompanied by increased macrophage recruitment and nucleotide‐binding domain leucine‐rich repeat and pyrin domain containing receptor 3 (NLRP3) inflammasome activation. Moreover, inhibiting the IL‐23/IL‐17 axis reduced the number of macrophage and the expression and activation of NLRP3 inflammasome. On the other hand, recombinant (r) IL‐23p19 and rIL‐17A promoted the expression and activation of NLRP3 inflammasome, and the proliferation and migration of macrophages. Furthermore, macrophage elimination decreased the activation of IL‐23/IL‐17 axis and the expression and activation of NLRP3 inflammasome. In summary, our experiments showed that the IL‐23/IL‐17 axis promoted the formation of RNV by activating the NLRP3 inflammasome in retinal macrophages of an OIR mouse model. [ABSTRACT FROM AUTHOR]

Summary: Dysfunction of the immune system underlies a plethora of human diseases, requiring the development of immunomodulatory therapeutic intervention. To date, most strategies employed have been focusing on the modification of T lymphocytes, and although remarkable improvement has been obtained, results often fall short of the intended outcome. Recent cutting‐edge technologies have highlighted macrophages as potential targets for disease control. Macrophages play central roles in development, homeostasis and host defence, and their dysfunction and dysregulation have been implicated in the onset and pathogenesis of multiple disorders including cancer, neurodegeneration, autoimmunity and metabolic diseases. Recent advancements have led to a greater understanding of macrophage origin, diversity and function, in both health and disease. Over the last few years, a variety of strategies targeting macrophages have been developed and these open new therapeutic opportunities. Here, we review the progress in macrophage reprogramming in various disorders and discuss the potential implications and challenges for macrophage‐targeted approaches in human disease. [ABSTRACT FROM AUTHOR]

In this paper we describe the effect of depletion of splenic macrophages on the uptake, and immune response against, different formulations of rabies virus antigen. Splenic macrophages were removed by intravenous injection with clodronate liposomes. β-propiolacton inactivated rabies virus (RV-BPL) and immune-stimulating complexes (iscom) containing these antigens were given to macrophage-depleted and control mice. In the absence of phagocytic cells in the spleen, antigen is still trapped in the red pulp and to a lesser extent in the peri-arteriolar lymphocyte sheaths (PALS) for both antigen formulations. The localization pattern in the main area of immune response induction, namely the follicles, was unaltered after macrophage depletion. Functionally, the depletion of splenic and liver macrophages had no influence on the induction of specific antibody responses in both RV-BPL or RV-iscom immunized mice, even though the latter presentation form was clearly associated with specific localization in the marginal metallophillic macrophages. In RV-BPL immunized mice, macrophage depletion had no influence on proliferative T-cell responses. However, macrophage-depleted mice that were immunized with RV-iscom showed a significant decrease in proliferative T-cell responses. These results confirm existing ideas on the spleen as a physical filter rather than an induction site for humoral responses and shed new light on the efficient role of iscoms as antigen-presenting moieties in relation to their specific in vivo localization patterns and partial macrophage dependency. [ABSTRACT FROM AUTHOR]

Macrophages are cytotoxic to chicken embryonic fibroblasts without either previous activation or lymphocyte assistance, This cytotoxic activity (xenolysis) is expressed by non-activated macrophages from athymic mice as well as by pure macrophage populations. Neither macrophage lysate nor supernatants of macrophages cultivated with fibroblasts cause xenolysis. Unlike macrophage tumoricidal activity, killing of xenogeneic cells is not dependent on specific serum factors and is expressed by macrophages from a lipopolysaccharide (LPS) unresponsive strain (C3H/HeJ). Xenolysis is expressed also by trypsin-treated macrophages and by macrophages from 5-day-old cultures. Killing of chicken fibroblasts by macrophages is not affected by hydrocortisone (100 μg/ml) gold salt (1 mg/ml) and colchicine (100 μg/ml), On the other hand, cytochalasin B (10 μg/ml) completely abolishes the killing, probably by interfering with macrophage mobility and extension of filopodia toward the targets. It is suggested that the xenolytic activity of macrophages represents a primitive trait of phagocytes which assists the body in defence against multicellular parasites. [ABSTRACT FROM AUTHOR]

Experiments are described which show that effete red cells will not adhere to autochthonous macrophages which have been treated with trypsin. If, following trypsin treatment, the macrophages are incubated in the presence of normal guinea-pig serum, activity is restored and the adherence reaction with effete red cells can again be demonstrated. Activity is not restored by incubation with Hanks's solution following trypsin treatment. These results suggest that the adherence reaction is mediated by a component of normal guinea-pig serum which becomes adsorbed to the macrophage surface. Evidence is presented suggesting that the linkage between the serum component and the macrophage surface is protein in nature. The active component is removed from guinea-pig serum by absorption with effete red cells. [ABSTRACT FROM AUTHOR]

Peritoneal exudate lymphocytes (PEL) of guinea-pigs injected with Freund's complete adjuvant (FCA) were capable of liberating skin reactive factor (SRF) and macrophage migration-inhibitory factor (MIF) when cultured for 24 hours in the presence of sheep red cells (SRC) preincubated with lymph node cells (LNC) of guinea-pigs immunized with SRC in FCA. Similar release of soluble mediators was found in the following situations: (a) incubation of non-immune PEL with SRC sensitized with the exclusion peak of Sephadex G-200 fractionated immune LNC supernatant; (b) incubation of non-immune LNC with complexes of SRC and anti-SRC IgG, prepared from serum of animals immunized with SRC in CFA, and (c) incubation of non-immune LNC with a mixture of SRc urea extract and anti-SRC IgG. SRC incubated for 24 hours with immune LNC and freed of lymphocytes by selective filtration through a Millipore filter, were able to provoke an inflammatory reaction in the skin of normal guinea-pigs, which was delayed in character. These findings are interpreted as suggestive evidence for the non-identity of the mediator-producing and antigen-reactive cells and as support for the hypothesis that a complex composed of antigen and an antibody-like material, secreted by stimulated antigen-reactive lymphocutes, is responsible for the release of soluble mediators in cell-mediated immune reactions. [ABSTRACT FROM AUTHOR]

Summary: Toll‐like receptor (TLR) 4 signalling is critical for innate immunoinflammatory response and widely triggers the development of various types of clinical diseases. MicroRNA‐7 (miR‐7) is well documented to play an important regulatory role in various biological events. However, the exact role of miR‐7 in TLR4 signalling pathway remains to be fully elucidated. In the present study, we found that miR‐7 expression in TLR4 signalling‐activated bone marrow‐derived macrophages (BMDMs) stimulated by LPS was dramatically increased. Importantly, miR‐7 deficiency significantly enhanced the production of related inflammatory cytokines including IL‐1β, IL‐6 and IL‐12, as well as TNF‐α, on LPS‐activated BMDMs, accompanied by elevated transduction of TLR4 signalling including Myd88‐dependent and Myd88‐independent pathways, whereas miR‐7 overexpression significantly decreased the transduction of TLR4 signalling and the production of related inflammatory cytokines. Mechanistically, we identified family with sequence similarity 177, member A (FAM177A) as a novel target molecule of miR‐7. Furthermore, down‐regulation of FAM177A using RNAi could impair the transduction of TLR4 signalling. Finally, down‐regulation of FAM177A also reversed the effect of miR‐7 deficiency on TLR4 signalling transduction and production of related inflammatory cytokines on BMDMs. Therefore, we provide the new evidence that miR‐7 acts as a novel negative fine‐tuner in regulating TLR4 signalling pathways by targeting FAM177A, which might throw light on the basal understanding on the regulatory mechanism of TLR4 signalling and benefit the development of therapeutic strategies against related clinical diseases. [ABSTRACT FROM AUTHOR]

Summary: Hydrogen sulphide (H2S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H2S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H2S in particular, is increasingly being appreciated. Endogenous H2S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H2S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H2S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H2S studies in macrophages, and to discuss with focus on the therapeutic potential of H2S donors by targeting macrophages. The feasibility of H2S signalling component as a macrophage biomarker under disease conditions would be also discussed. [ABSTRACT FROM AUTHOR]

Summary: Macrophages are particularly abundant and play an important role throughout the tumor progression process, namely, tumor‐associated macrophages (TAM) in the tumor microenvironment. TAM can be polarized to disparate functional phenotypes, the M1 and M2 macrophages. M1‐like type macrophages are defined as pro‐inflammatory cells involved in killing cancer cells, while M2‐like type cells can specially promote tumor growth and metastasis, tissue remodeling and immunosuppression. In this study, we first found that integrin β3 was highly expressed on the surface of TAM, both in vivo and in vitro, that displayed the M2‐like characteristics. Under intervention of CYC or triptolide, the integrin β3 inhibitors, the M2 polarization of TAM could be inhibited. Moreover, in the cell model of M2 polarization, either blockade or knockout/knockdown of integrin β3 could also suppress macrophage M2 polarization, which suggested that the M2 polarization was dependent on integrin β3. Using knockdown of peroxisome proliferator‐activated receptor‐γ (PPARγ), an M2 regulator, we found that expression and activation of PPARγ participated in M2 polarization that was mediated by integrin β3. Finally, to verify the activity of integrin β3 inhibitors on TAM in vivo, 4T1 tumor‐bearing mice were treated with CYC or triptolide; in response, the M1/M2 ratio of TAM was up‐regulated, while the infiltration of total lymphocytes into tumor tissue was not altered. In general, our study found a connection between integrin β3 and macrophage polarization, which provides a strategy for facilitating M2 to M1 repolarization and reconstructing the tumor immune microenvironment. [ABSTRACT FROM AUTHOR]

Summary: The skin is the outermost layer of the body with an extensive surface area of approximately 1·8 m2, and is the first line of defence against a multitude of external pathogens and environmental insults. The skin also has important homeostatic functions such as reducing water loss and contributing to thermoregulation of the body. The structure of the skin and its cellular composition work in harmony to prevent infections and to deal with physical and chemical challenges from the outside world. In this review, we discuss how the structural cells such as keratinocytes, fibroblasts and adipocytes contribute to barrier immunity. We also discuss specialized immune cells that are resident in steady‐state skin including mononuclear phagocytes, such as Langerhans cells, dermal macrophages and dermal dendritic cells in addition to the resident memory T cells. Ageing results in an increased incidence of cancer and skin infections. As we age, the skin structure changes with thinning of the epidermis and dermis, increased water loss, and fragmentation of collagen and elastin. In addition, the skin immune composition is altered with reduced Langerhans cells, decreased antigen‐specific immunity and increased regulatory populations such as Foxp3+ regulatory T cells. Together, these alterations result in decreased barrier immunity in the elderly, explaining in part their increased susceptiblity to cancer and infections. [ABSTRACT FROM AUTHOR]

Summary: High salt consumption has since long been associated with elevated blood pressure and cardiovascular disease. Recently, mouse studies suggested that a high dietary salt intake exacerbates the clinical manifestations of autoimmunity. Using naïve cells ex vivo after pre‐exposure of mice to high salt intake, we showed that increased salt exposure affects the viability and effector functions of immune cells. CD4+ T‐cells evidenced a pro‐inflammatory phenotype characterized by increased secretion of IFNγ and IL‐17A, when exposed to high salt concentrations in vitro. Interestingly, this phenotype was associated with osmotic pressure, as replacing salt for d‐mannitol resulted in similar observations. However, high salt intake did not alter the development of T‐cell‐dependent autoimmunity. Instead, recruitment of peritoneal macrophages was increased in mice pre‐exposed to high salt concentrations. These cells had an increased production of both TNFα and IL‐10, suggesting that salt stimulates expansion and differentiation of different subsets of macrophages. Moreover, mice pre‐exposed to high salt intake developed exacerbated symptoms of colitis, when induced by dextran sulphate sodium. The aggravated colitis in salt‐exposed animals was associated with a higher frequency of CD4+ T‐cells and CD11b+ CD64+ macrophages producing TNFα. These phenotypes correlated with elevated titres of faecal IgA and higher lymphocytic cellularity in the colon, mesenteric lymph nodes and spleen. In conclusion, we report here that high salt intake affects both lymphoid and myeloid cells ex vivo. However, the effects of high salt intake in vivo seem less pronounced in terms of CD4+ T‐cell responses, whereas macrophage‐dependent pathologies are significantly influenced. [ABSTRACT FROM AUTHOR]

Summary: Macrophage activation is characterized by pronounced metabolic adaptation. Classically activated macrophages show decreased rates of mitochondrial fatty acid oxidation and oxidative phosphorylation and acquire a glycolytic state together with their pro‐inflammatory phenotype. In contrast, alternatively activated macrophages require oxidative phosphorylation and mitochondrial fatty acid oxidation for their anti‐inflammatory function. Although it is evident that mitochondrial metabolism is regulated during macrophage polarization and essential for macrophage function, little is known on the regulation and role of peroxisomal β‐oxidation during macrophage activation. In this study, we show that peroxisomal β‐oxidation is strongly decreased in classically activated bone‐marrow‐derived macrophages (BMDM) and mildly induced in alternatively activated BMDM. To examine the role of peroxisomal β‐oxidation in macrophages, we used Mfp2−/− BMDM lacking the key enzyme of this pathway. Impairment of peroxisomal β‐oxidation in Mfp2−/− BMDM did not cause lipid accumulation but rather an altered distribution of lipid species with very‐long‐chain fatty acids accumulating in the triglyceride and phospholipid fraction. These lipid alterations in Mfp2−/− macrophages led to decreased inflammatory activation of Mfp2−/− BMDM and peritoneal macrophages evidenced by impaired production of several inflammatory cytokines and chemokines, but did not affect anti‐inflammatory polarization. The disturbed inflammatory responses of Mfp2−/− macrophages did not affect immune cell infiltration, as mice with selective elimination of MFP2 from myeloid cells showed normal monocyte and neutrophil influx upon challenge with zymosan. Together, these data demonstrate that peroxisomal β‐oxidation is involved in fine‐tuning the phenotype of macrophages, probably by influencing the dynamic lipid profile during macrophage polarization. [ABSTRACT FROM AUTHOR]

Inflammatory responses mediated by macrophages are part of the innate immune system, whose role is to protect against invading pathogens. Lipopolysaccharide ( LPS) found in the outer membrane of Gram-negative bacteria stimulates an inflammatory response by macrophages. During the inflammatory response, extracellular LPS is recognized by Toll-like receptor 4, one of the pattern recognition receptors that activates inflammatory signalling pathways and leads to the production of inflammatory mediators. The innate immune response is also triggered by intracellular inflammasomes, and inflammasome activation induces pyroptosis and the secretion of pro-inflammatory cytokines such as interleukin-1 β ( IL-1 β) and IL-18 by macrophages. Cysteine-aspartic protease (caspase)-11 and the human orthologues caspase-4/caspase-5 were recently identified as components of the 'non-canonical inflammasome' that senses intracellular LPS derived from Gram-negative bacteria during macrophage-mediated inflammatory responses. Direct recognition of intracellular LPS facilitates the rapid oligomerization of caspase-11/4/5, which results in pyroptosis and the secretion of IL-1 β and IL-18. LPS is released into the cytoplasm from Gram-negative bacterium-containing vacuoles by small interferon-inducible guanylate-binding proteins encoded on chromosome 3 ( GBPchr3)-mediated lysis of the vacuoles. In vivo studies have clearly shown that caspase-11 −/− mice are more resistant to endotoxic septic shock by excessive LPS challenge. Given the evidence, activation of caspase-11 non-canonical inflammasomes by intracellular LPS is distinct from canonical inflammasome activation and provides a new paradigm in macrophage-mediated inflammatory responses. [ABSTRACT FROM AUTHOR]

Macrophages and dendritic cells ( DCs) in murine spleen are essential for the maintenance of immune homeostasis by elimination of blood-borne foreign particles and organisms. It has been reported that splenic DCs, especially CD8 α+ CD103+ DCs, are responsible for tolerance to apoptosis-associated antigens. However, the molecular mechanism by which these DCs maintain immune homeostasis by blood-borne apoptotic cell clearance remains elusive. Here, we found that the CCL22/ CCR4 axis played a critical role in the maintenance of immune homeostasis during apoptotic cell clearance by splenic CD8 α+ CD103+ DCs. The present results revealed that systemic administration of apoptotic cells rapidly induced a large number of CCL22 and CCR4+ regulatory T (Treg) cells in the spleen of C57 BL/6J mice. Further study demonstrated that CD8 α+ CD103+ DCs dominantly produce much higher CCL22 than CD8 α+ CD103− DCs. Moreover, the transient deletion of CD8 α+ CD103+ DCs caused a decrease in CCL22 levels together with CCR4+ Treg cell percentage. Subsequently, the levels of some pro-inflammatory cytokines, such as interleukin-17 and interferon- γ in the spleen with the absence of CD8 α+ CD103+ DCs increased in response to the administration of apoptotic cells. Hence, intravenous injection of apoptotic cells induced a subsequent increase in CCL22 expression and CCR4+ Treg cells, which contribute to the maintenance of immune homeostasis at least partially by splenic CD8 α+ CD103+ DCs. [ABSTRACT FROM AUTHOR]

The precise mechanisms responsible for immunosenescence still remain to be determined, however, considering the evidence that disruption of the organization of primary and secondary lymphoid organs results in immunodeficiency, we propose that this could be involved in the decline of immune responses with age. Therefore, we investigated the integrity of the splenic microarchitecture in mice of increasing age and its reorganization following immune challenge in young and old mice. Several differences in the anatomy of the spleen with age in both the immune and stromal cells were observed. There is an age-related increase in the overall size of the white pulp, which occurs primarily within the T-cell zone and is mirrored by the enlargement of the T-cell stromal area, concurrent to the distinct boundary between T cells and B cells becoming less defined in older mice. In conjunction, there appears to be a loss of marginal zone macrophages, which is accompanied by an accumulation of fibroblasts in the spleens from older animals. Furthermore, whereas the reorganization of the white pulp is resolved after several days following antigenic challenge in young animals, it remains perturbed in older subjects. All these age-related changes within the spleen could potentially contribute to the age-dependent deficiencies in functional immunity. [ABSTRACT FROM AUTHOR]

Understanding the nature of adjuvants and the immune priming events in autoimmune diseases, such as rheumatoid arthritis, is a key challenge to identify their aetiology. Adjuvants are, however, complex structures with inflammatory and immune priming properties. Synthetic polymers provide a possibility to separate these functions and allow studies of the priming mechanisms in vivo. A well-balanced polymer, poly-N-isopropyl acrylamide (PNiPAAm) mixed with collagen type II (CII) induced relatively stronger autoimmunity and arthritis compared with more hydrophilic (polyacrylamide) or hydrophobic (poly-N-isopropylacrylamide-co-poly-N-tertbutylacrylamide and poly-N-tertbutylacrylamide) polymers. Clearly, all the synthesized polymers except the more hydrophobic poly-N-tertbutylacrylamide induced arthritis, especially in Ncf1-deficient mice, which are deficient in reactive oxygen species (ROS) production. We identified macrophages as the major infiltrating cells present at PNiPAAm-CII injection sites and demonstrate that ROS produced by the macrophages attenuated the immune response and the development of arthritis. Our results reveal that thermo-responsive polymers with high immune priming capacity could trigger an autoimmune response to CII and the subsequent arthritis development, in particular in the absence of NOX2 derived ROS. Importantly, ROS from macrophages protected against the autoimmune priming, demonstrating a critical regulatory role of macrophages in immune priming events. [ABSTRACT FROM AUTHOR]

Dengue virus ( DENV) infection causes dengue fever, dengue haemorrhagic fever, or dengue shock syndrome. Mast cells have been speculated to play a role in DENV disease although their precise roles are unclear. In this study, we used mast cell-deficient KitW-sh/W-sh mice to investigate the involvement of mast cells after intradermal DENV infection. An approximately two- to three-fold higher level of DENV NS3 antigen was detected at the skin inoculation site in DENV-infected KitW-sh/W-sh mice than in DENV-infected wild-type ( WT) mice (using a dose of 1 × 109 plaque-forming units/mouse). Moreover, as an indicator of heightened pathogenesis, a more prolonged bleeding time was observed in DENV-infected KitW-sh/W-sh mice than in WT mice. Monocytes/macrophages are considered to be important targets for DENV infection, so we investigated the susceptibility and chemokine response of DENV-infected peritoneal macrophages from KitW-sh/W-sh and WT mice both ex vivo and in vivo. There was a tendency for higher DENV infection and higher secretion of CCL2 ( MCP-1) from peritoneal macrophages isolated from KitW-sh/W-sh mice than those from WT mice. In vivo studies using intradermal inoculation of DENV showed about twofold higher levels of infiltrating macrophages and CCL2 ( MCP-1) at the inoculation site in both mock control and DENV-inoculated KitW-sh/W-sh mice than in corresponding WT mice. In summary, compared with WT mice, KitW-sh/W-sh mice show enhanced DENV infection and macrophage infiltration at the skin inoculation site as well as increased DENV-associated bleeding time. The results indicate an intriguing interplay between mast cells and tissue macrophages to restrict DENV replication in the skin. [ABSTRACT FROM AUTHOR]

Macrophages play important roles in the innate immune system during infection and systemic inflammation. When bacterial lipopolysaccharide ( LPS) binds to Toll-like receptor 4 on macrophages, several signalling cascades co-operatively up-regulate gene expression of inflammatory molecules. The present study aimed to examine whether salt-inducible kinase [ SIK, a member of the AMP-activated protein kinase ( AMPK) family] could contribute to the regulation of immune signal not only in cultured macrophages, but also in vivo. LPS up-regulated SIK3 expression in murine RAW264.7 macrophages and exogenously over-expressed SIK3 negatively regulated the expression of inflammatory molecules [interleukin-6 ( IL-6), nitric oxide ( NO) and IL-12p40] in RAW264.7 macrophages. Conversely, these inflammatory molecule levels were up-regulated in SIK3-deficient thioglycollate-elicited peritoneal macrophages ( TEPM), despite no impairment of the classical signalling cascades. Forced expression of SIK3 in SIK3-deficient TEPM suppressed the levels of the above-mentioned inflammatory molecules. LPS injection (10 mg/kg) led to the death of all SIK3-knockout ( KO) mice within 48 hr after treatment, whereas only one mouse died in the SIK1- KO ( n = 8), SIK2- KO ( n = 9) and wild-type ( n = 8 or 9) groups. In addition, SIK3- KO bone marrow transplantation increased LPS sensitivity of the recipient wild-type mice, which was accompanied by an increased level of circulating IL-6. These results suggest that SIK3 is a unique negative regulator that suppresses inflammatory molecule gene expression in LPS-stimulated macrophages. [ABSTRACT FROM AUTHOR]

Summary: When monocytes migrate from blood into tissues they differentiate into macrophage‐like cells. The outcome of this differentiation process is strongly influenced by the tissue environment, and the macrophages produced help control the immunological properties of the tissue. The process of monocyte–macrophage differentiation is therefore potentially attractive when seeking therapeutic targets to amplify or modulate the inflammatory response. Here we highlight recent research in this area, identifying the gene Paqr11 as an important factor in monocyte differentiation, and therefore an important potential target for reducing macrophage‐mediated inflammation in arthritis. [ABSTRACT FROM AUTHOR]

Prions are a unique group of pathogens, which are considered to comprise solely of an abnormally folded isoform of the cellular prion protein. The accumulation and replication of prions within secondary lymphoid organs is important for their efficient spread from the periphery to the brain where they ultimately cause neurodegeneration and death. Mononuclear phagocytes ( MNP) play key roles in prion disease pathogenesis. Some MNP appear to facilitate the propagation of prions to and within lymphoid tissues, whereas others may aid their clearance by phagocytosis and by destroying them. Our recent data show that an intact splenic marginal zone is important for the efficient delivery of prions into the B-cell follicles where they subsequently replicate upon follicular dendritic cells before infecting the nervous system. Sialoadhesin is an MNP-restricted cell adhesion molecule that binds sialylated glycoproteins. Sialoadhesin is constitutively expressed upon splenic marginal zone metallophilic and lymph node sub-capsular sinus macrophage populations, where it may function to bind sialylated glycoproteins, pathogens and exosomes in the blood and lymph via recognition of terminal sialic acid residues. As the prion glycoprotein is highly sialylated, we tested the hypothesis that sialoadhesin may influence prion disease pathogenesis. We show that after peripheral exposure, prion pathogenesis was unaltered in sialoadhesin-deficient mice; revealing that lymphoid sequestration of prions is not mediated via sialoadhesin. Hence, although an intact marginal zone is important for the efficient uptake and delivery of prions into the B-cell follicles of the spleen, this is not influenced by sialoadhesin expression by the MNP within it. [ABSTRACT FROM AUTHOR]

The rapid differentiation of monocytes into macrophages ( MΦ) and dendritic cells is a pivotal aspect of the innate immune response. Differentiation is triggered following recognition of microbial ligands that activate pattern recognition receptors or directly by pro-inflammatory cytokines. We demonstrate that interleukin-1β ( IL-1β) induces the rapid differentiation of monocytes into CD209+ MΦ, similar to activation via Toll-like receptor 2/1, but with distinct phenotypic and functional characteristics. The IL-1β induced MΦ express higher levels of key markers of phagocytosis, including the Fc-receptors CD16 and CD64, as well as CD36, CD163 and CD206. In addition, IL-1β-induced MΦ exert potent phagocytic activity towards inert particles, oxidized low-density lipoprotein and mycobacteria. Furthermore, IL-1β-induced MΦ express higher levels of HLA- DR and effectively present mycobacterial antigens to T cells. Therefore, the ability of IL-1β to induce monocyte differentiation into MΦ with both phagocytosis and antigen-presenting function is a distinct part of the innate immune response in host defence against microbial infection. [ABSTRACT FROM AUTHOR]

Hepatitis C virus (HCV) is remarkably efficient at evading host immunity to establish chronic infection. During chronic HCV infection, interleukin-12 (IL-12) produced by monocytes/macrophages (M/Mφ) is significantly suppressed. Programmed death-1 (PD-1), an inhibitory receptor on immune cells, plays a pivotal role in suppressing T-cell responses during chronic viral infection. To determine whether PD-1 regulates IL-12 production by M/Mφ during chronic HCV infection, we examined the expressions of PD-1, its ligand PDL-1, and their relationship with IL-12 production in M/Mφ from HCV-infected, HCV-resolved, and healthy subjects by flow cytometry. Toll-like receptor (TLR) -mediated IL-12 production by M/Mφ was selectively suppressed, while PD-1/PDL-1 expressions were up-regulated, in HCV-infected subjects compared with HCV-resolved or healthy subjects. Up-regulation of PD-1 was inversely associated with the degree of IL-12 inhibition in HCV infection. Interestingly, the reduced response of M/Mφ from HCV-infected individuals to TLR ligands appeared not to be the result of a lack of the ability to sense pathogen, but to an impaired activation of intracellular janus kinase/signal transducer and activator of transfection (STAT) pathway as represented by inhibited STAT-1 phosphorylation in M/Mφ from HCV-infected individuals compared with HCV-negative subjects. Successful HCV treatment with pegylated interferon/ribavirin or blocking PD-1/PDL-1 engagement ex vivo led to reduced PD-1 expression and improved IL-12 production as well as STAT-1 activation in M/Mφ from HCV-infected individuals. These results suggest that the PD-1 inhibitory pathway may negatively regulate IL-12 expression by limiting STAT-1 phosphorylation in M/Mφ during chronic HCV infection. [ABSTRACT FROM AUTHOR]

Macrophages (Mϕ) are professional antigen-presenting cells, but when they accumulate at sites of inflammation, they can inhibit T-cell proliferation. In experimental autoimmune uveoretinitis, this limits the expansion of T cells within the target organ. To define requirements for the elaboration of this outcome, we have generated populations of Mϕ in vitro that could also regulate T-cell responses; stimulating CD4+ T-cell activation and cytokine production, but simultaneously suppressing T-cell proliferation. When T cells are removed from the influence of such cells, normal T-cell responses are restored. We show that tumour necrosis factor 1 (TNFR1) signalling is a critical checkpoint in the development of such Mϕ, as TNFR1−/− Mϕ are unable to suppress T-cell proliferation. This deficit in antigen-presenting cells results in a lack of production of prostaglandin E2 (PGE2) and nitric oxide, which are critical effector mechanisms that inhibit T-cell division. However, TNFR1 signalling is not required for the inhibitory function of Mϕ because we could circumvent the requirement for this receptor, by maturing Mϕ in the presence of exogenous interferon-γ and PGE2. This produced TNFR1−/− Mϕ that inhibited T-cell proliferation and indicates that TNFR1 delivers a signal that is necessary for the development but not the execution of this function. [ABSTRACT FROM AUTHOR]

Toll-like receptor-3 (TLR-3) recognizes double-stranded RNA and induces multiple intracellular events responsible for innate anti-viral immunity against a number of viral infections. Activation of TLR-3 inhibits human immunodeficiency virus (HIV) replication, but the mechanism(s) underlying the action of TLR-3 activation on HIV are largely unknown. Here we demonstrate that treatment of monocyte-derived macrophages with poly I:C, a synthetic ligand for TLR-3, significantly inhibited HIV infection and replication. Investigation of the mechanisms showed that TLR-3 activation resulted in the induction of type I interferon inducible antiviral factors, including APOBEC3G and tetherin, the newly identified anti-HIV cellular proteins. In addition, poly I:C-treated macrophages expressed increased levels of CC chemokines, the ligands for CCR5. Furthermore, TLR-3 activation in macrophages induced the expression of cellular microRNAs (miRNA-28, -125b, -150, -223 and -382), the newly identified intracellular HIV restriction factors. These findings indicate that TLR-3-mediated induction of multiple anti-HIV factors should be beneficial for the treatment of HIV disease where innate immune responses are compromised by the virus. [ABSTRACT FROM AUTHOR]

While it is known that the anti-inflammatory effects of interleukin (IL)-4 require new protein synthesis, the exact mechanisms by which IL-4 suppresses the production of pro-inflammatory cytokines by human monocytes and macrophages is unclear. IL-4 rapidly induced suppressor of cytokine signalling-1 (SOCS1) mRNA and protein, which peaked at 60 min, much earlier than lipopolysaccharide (LPS)-induced SOCS1 mRNA and protein which were consistently maximal 4 hr post-exposure. SOCS1 is a molecule generally considered to be induced for negative feedback of inflammatory processes. We investigated whether the early induction of SOCS1 by IL-4 was responsible for the suppression of LPS-induced tumour necrosis factor (TNF)-α production by IL-4. IL-4 suppressed LPS-induced TNF-α in freshly isolated monocytes at the level of transcription but acted by a different, possibly translational, mechanism in monocytes cultured overnight in macrophage colony-stimulating factor (M-CSF). Despite different modes of regulation by IL-4, the kinetics and magnitude of induction of SOCS1 mRNA and protein by IL-4 in the two cell types were identical. There was no significant difference in the suppression by IL-4 of LPS-induced TNF-α production by bone-marrow derived macrophages from wild-type mice, Ifnγ−/− mice and mice lacking SOCS1 ( Socs1−/− Ifnγ−/−). These data suggest that SOCS1 is not involved in the suppression of LPS-induced TNF-α production by IL-4. [ABSTRACT FROM AUTHOR]