In vitro prevention and reversal of lipopolysaccharide desensitization by IFN-gamma, IL-12, and granulocyte-macrophage colony-stimulating factor

LPS tolerance is characterized by a diminished monocytic synthesis of TNF-alpha and, interestingly, IL-10 after LPS restimulation. We wondered whether granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-12, and IFN-gamma can prevent or reverse this down-regulation of TNF-alpha and IL-10 production. The LPS-induced TNF-alpha amounts in desensitized PBMC treated with GM-CSF, IFN-gamma, or IL-12 and in naive, non-cytokine-primed cultures were similar, while much more TNF-alpha was induced in cytokine-primed naive cells. The effect of IL-12 was dependent on the presence of nonmonocytic cells and could be completely blocked with an IFN-gamma antiserum. Treatment of LPS-desensitized pure monocytes with IFN-gamma or GM-CSF resulted in a very high TNF-alpha expression and no difference to cytokine-primed naive monocytes was evident any longer. While IFN-gamma and IL-12 decreased IL-10 expression in naive PBMC, it was increased by both and by GM-CSF in LPS-tolerant cultures. Again, only IL-12 was dependent on the presence of nonmonocytic cells. For prevention of LPS tolerance, similar results were obtained. Recently, we have shown that IL-10 and TGF-beta mediate LPS desensitization in vitro and can be used to establish LPS hyporesponsiveness in the absence of LPS. IFN-gamma and GM-CSF prevented and reversed down-regulation of TNF-alpha and IL-10 synthesis also in the model of IL-10/TGF-beta1-induced LPS hyporesponsiveness, while IL-12 was ineffective because of its obvious inability to induce IFN-gamma. In summary, after LPS desensitization/hyporesponsiveness, IFN-gamma and GM-CSF tended to normalize pro- and anti-inflammatory monocytic behavior. Our results suggest that during LPS desensitization/hyporesponsiveness, monocytes acquire a hitherto unknown functional state with an altered reaction to biologic response modifiers.     

Antigen-driven but not lipopolysaccharide-driven IL-12 production in macrophages requires triggering of CD40

We demonstrated that two distinct pathways exist for the induction of IL-12 in APC. The first pathway for IL-12 production occurred during responses to T cell-dependent Ags such as OVA and required triggering of CD40 molecules on the APC. IL-12 production in this T cell-dependent system increased in direct proportion to Ag concentration and required TCR ligation but not CD28 costimulation. The second pathway occurred when bacterial products such as LPS or heat-killed Listeria monocytogenes were used to activate macrophages to produce IL-12 in the complete absence of T cells. In this second pathway, IL-12 production was completely independent of CD40 triggering. In both pathways, the presence of IFN-gamma was not required for induction of IL-12 synthesis when splenic adherent cells (SAC) from normal mice were used. However, addition of IFN-gamma to cultures of Th2 T cells and SAC increased IL-12 production two- to fivefold, and addition of rTNF-alpha with IFN-gamma further enhanced IL-12 production. The addition of TNF-alpha in the absence of IFN-gamma, however, had no effect on IL-12 production in the T cell-dependent pathway. Similarly, addition of TNF-alpha in the presence or the absence of IFN-gamma to cultures of LPS or heat-killed Listeria and SAC did not increase IL-12 production, but addition of IFN-gamma alone greatly enhanced IL-12 production, consistent with the idea that bacterial stimuli induce significant quantities of endogenous TNF-alpha production. These results indicate that the requirements for the induction of IL-12 production in T cell-dependent and T cell-independent responses differs mainly with regard to CD40 triggering. Furthermore, these results suggest that IL-12 production can be induced by bacterial products in patients with hyper-IgM syndrome who lack CD40 ligand expression and in those treated with soluble gp39 to interrupt CD40-CD40 ligand interactions.     

RNA-binding protein conserved in both microtubule- and microfilament-based RNA localization

IL-12 is a key cytokine in the development of Th1 responses. IL-12 production by antigen-presenting cells (APC) can be induced by the interaction between CD40 on the APC and CD40 ligand (CD40L) expressed on T cells after activation. Our previous study indicated that in dendritic cells (DC), the only APC that can activate naive T(h) cells efficiently, the mere CD40 engagement is insufficient to induce IL-12 production. The aim of the present study was to dissect the conditions for efficient IL-12 production by DC further. Using populations of naive and memory Th cells, recombinant CD40L, neutralizing and blocking antibodies, and by determining IFN-gamma production and CD40L expression levels, we here show that T cell-induced IL-12 production by DC results from the action of two signals, mediated by CD40L and IFN-gamma, and that the inability of naive T(h) cells to induce IL-12 production resides in their inability to produce IFN-(gamma). Other factors than CD40L and IFN-gamma can provide the required signals for IL-12 production by DC, as either factor could be replaced by lipopolysaccharide (LPS). The two-signal requirement proved unique for the production of IL-12, since either CD40 engagement or LPS was sufficient for the efficient production of tumor necrosis factor-alpha, IL-8 and the p40 subunit of IL-12, and may be considered as a safety mechanism for optimal control of potentially harmful T(h)1 responses.     

Evidence for a unique elastic sheath surrounding the vesicular arteries of the rabbit urinary bladder--studies of the microvasculature with microscopy and vascular corrosion casting

AD is associated with a bias of the T helper cells to show increased IL-4 and reduced interferon-gamma (IFN-gamma) production. The production of IFN-gamma and IL-4 and the development of Th cells into either high IFN-gamma or high IL-4 producers is strongly influenced by factors produced by antigen-presenting cells (APC), like IL-12 and prostaglandin E2 (PGE2). IL-12 selectively enhances IFN-gamma production and favours the development of IFN-gamma-producing Th cells, whereas PGE2 selectively inhibits IFN-gamma production by Th cells. The aim of this study was to test whether the increased IL-4/IFN-gamma production ratio by Th cells in AD can be explained by an increased PGE2/IL-12 production ratio by the APC. Monocytes were used as APC source. PGE2 and IL-12 production by lipopolysaccharide (LPS)-stimulated monocytes from 12 AD patients and 12 non-atopic controls was determined using two complementary experimental systems, whole blood cultures and purified monocytes. In addition, we determined IL-6 production as a measure of monocyte activation, and IL-10 production because IL-12 production by monocytes is highly influenced by endogenously produced IL-10. The monocytes from AD patients showed normal production levels of IL-6 and IL-10, a two-fold, but non-significant decrease in IL-12 production, and a significantly (three-fold) higher PGE2 production than those from non-atopic controls. Here we show for the first time that enhanced PGE2 production by monocytes in AD is not accompanied by a general rise in cytokine production. We conclude that AD is indeed associated with an increased PGE2/IL-12 production ratio by monocytes.     

Regulation of IFN-gamma production in granulocyte-macrophage colony-stimulating factor-deficient mice

Granulocyte-macrophage colony-stimulating factor-deficient (GM-CSF-/-) mice produce far lower serum levels of IFN-gamma in response to LPS than GM-CSF+/+ mice. CD4+ and CD8+ T cells from LPS-injected GM-CSF-/- mice showed a deficiency in IFN-gamma production and proliferative activity in response to IL-2 and IL-12, whereas IFN-gamma production by NK cells was not compromised. These defects of T cells were reversed by administration of GM-CSF in vivo, but not by supplementation with GM-CSF in vitro. GM-CSF-/- mice do not have an intrinsic defect in IFN-gamma production, because IL-12 injection induces the same high levels of IFN-gamma in GM-CSF-/- and GM-CSF+/+ mice. To investigate the inhibitory effect of LPS on GM-CSF-/- T cells and the indirect restorative activity of GM-CSF, we tested the action of supernatants from cultured dendritic cells (DC). A factor or factors in the DC supernatant normalized serum IFN-gamma levels and T cell responses in LPS-injected GM-CSF-/- mice. IL-18 reproduced some but not all of these in vivo and in vitro effects of DC supernatants. Our results indicate that GM-CSF is important in protecting T cells from inhibitory signals generated during immunization or exposure to LPS, and that this effect of GM-CSF is indirect and mediated by factors produced by DC.     

Effects of macrophage colony-stimulating factor (M-CSF) on lipopolysaccharide (LPS)-induced mediator production from monocytes in vitro

M-CSF is a macrophage-lineage-specific growth factor that causes proliferation and differentiation of progenitor cells in the bone marrow. To investigate the effects of M-CSF on more matured cells, human monocytes were cultured in the presence or absence of M-CSF for 6 days. Addition of M-CSF at more than 10(2) U/ml resulted in higher viability and caused morphological differentiation to large macrophage-like cells. LPS-induced mediator production was also compared between M-CSF-treated and control cell. Monocytes were incubated with or without M-CSF for 3 days, and were stimulated with 1 microgram/ml of LPS for 2 days. IL-1 beta was not detected in the both culture supernatants, and PGE2 production was not influenced by M-CSF. However, amounts of G-CSF, GM-CSF, IL-6, and TNF-alpha produced in response to 1 microgram/ml of LPS were 1.5 to 2 times greater from monocytes treated with 10(4) U/ml of M-CSF than from control cells. The priming effect of M-CSF on LPS-induced cytokine production was found to require 3-day preincubation, and reached a maximum at the concentration of 10(4) U/ml. M-CSF-treated cells responded to a 10 times lower concentration of LPS than control cells in terms of cytokine production. M-CSF was also shown by flowcytometric analysis to influence the expression of CD14, a receptor for LPS, which might render monocytes more sensitive to LPS.     

IFN-alpha priming of human monocytes differentially regulates gram-positive and gram-negative bacteria-induced IL-10 release and selectively enhances IL-12p70, CD80, and MHC class I expression

Administration of IFN-gamma and IFN-alpha may protect or induce autoimmune diseases. Although the in vitro regulation of monokine secretion by IFN-gamma have been extensively studied, the regulatory function of IFN-alpha has not yet been elucidated. We compared IFN-alpha and IFN-gamma, added alone or simultaneously before bacterial stimulation, for the control of monokine release and the expression of costimulatory molecules by human monocytes. Our data show that: 1) IFN-alpha primes monocytes for increased production of IL-10 in response to Staphylococcus aureus Cowan I strain (SAC) but not to LPS, leading to a lack of IFN-alpha priming for TNF-alpha secretion; 2) pretreatment of monocytes with IFN-alpha inhibits LPS- or SAC-induced IL-12p40 production but unexpectedly enhances the release of the biologically active form of IL-12 (IL-12p70); 3) IFN-alpha and IFN-gamma exert an antagonistic effect on LPS- and SAC-induced IL-10 as well as IL-12p40 release, whereas they further enhance IL-12p70 production when added simultaneously; 4) in contrast to IFN-alpha, IFN-gamma primes monocytes to enhance LPS- or SAC-induced TNF-alpha and IL-12 production, but surprisingly, it increases IL-10 production by monocytes following LPS but not SAC stimulation; and finally, 5) IFN-alpha pretreatment selectively up-regulates CD80 and MHC class I expression on monocytes. It is proposed that the outcome of the immune response at the site of inflammation may depend on both the type of bacterial injury (gram-positive or -negative) and of locally produced IFNs, and that the differential and opposite effects of type I and type II IFNs on monocytes may account for the beneficial or detrimental effects of IFN-alpha therapy.     

Alleviation of lipopolysaccharide-induced acute liver injury in Propionibacterium acnes-primed IFN-gamma-deficient mice by a concomitant reduction of TNF-alpha, IL-12, and IL-18 production

The present study was designed to investigate the role of IFN-gamma in LPS-induced liver injury following priming with Propionibacterium acnes. At 1 week after priming BALB/c mice with P. acnes, a large number of macrophages (Mphi) and lymphocytes predominantly infiltrated the portal area, resulting in the intrahepatic formation of granulomas consisting of epithelioid and lymphoid cells. In comparison, in IFN-gamma gene-disrupted BALB/c mice (IFN-gamma knockout mice), the number of infiltrated Mphi was decreased, with a significant reduction in the number and size of granulomas. Subsequent elicitation with a low dose of LPS induced massive hepatic necrosis in wild-type BALB/c mice, with a marked increase in the serum levels of TNF-alpha, IL-12, and IL-18 and subsequently of alanine transferase. In contrast, IFN-gamma knockout mice developed scattered focal necrosis of the liver with significantly lower levels of serum alanine transferase as well as drastic decreases in TNF-alpha, IL-12, and IL-18 production. The administration of an anti-IFN-gamma neutralizing mAb at the eliciting phase significantly alleviated liver injury and reduced serum IL-12 and IL-18 levels. Thus, endogenously produced IFN-gamma is involved in the pathogenesis of this liver injury model by regulating Mphi infiltration and granuloma formation in the priming phase as well as cytokine production in the eliciting phase.     

Erratum to "Immunocytochemical detection of cytokines and chemokines in Langerhans cells and in vitro derived dendritic cells"

We have developed a direct immunocytochemical technique to identify cytokine and chemokine production in epidermal Langerhans cells (LC) and in vitro derived CD14-, CD1a+, CD83+, CD40+ dendritic cells (DC) at the single cell level. Formaldehyde fixation combined with saponin permeabilization preserved cellular morphology and generated a characteristic juxtanuclear staining signal due to the accumulation of cytokine to the Golgi organelle. This approach was used for the assessment of TNF-alpha, IL-6, IL-8, IL-10, IL-12, GM-CSF, MIP-1alpha, MIP-1beta and RANTES producing cells. In contrast, a diffuse cytoplasmic staining was evident for IL-1ra, IL-1alpha and IL-1beta production. IL-1ra and IL-1alpha were expressed in 10-25% of unstimulated cultured cells, while all the other cytokines were undetectable. IL-1ra, IL-1alpha and IL-1beta were also the dominating cytokines, expressed in up to 85% of the DC, after 3 h of LPS stimulation. A significantly lower number of cells (0-5%) synthesized TNF-alpha, IL-6, IL-10, IL-12 and GM-CSF. The incidence of chemokine producing cells (IL-8, RANTES, MIP-1alpha, MIP-1beta) peaked 10 h after LPS stimulation in up to 60% of the DC. Both immature CD83- and mature CD83+ DC as well as LC had a similar cytokine production pattern. Thus, in comparison to monocytes, LPS stimulation of DC generated a lower incidence of TNF-alpha, IL-6, IL-10 and IL-12 producing cells while IL-1 was expressed in a comparable number of cells.     

Reduced IL-12 production by monocytes upon ultraviolet-B irradiation selectively limits activation of T helper-1 cells

The capacity of APC to stimulate the proliferation of human peripheral blood T cells decreases upon ultraviolet-B (UVB) irradiation. The aim of this study was to investigate whether all T cell subsets are equally sensitive to this reduced APC function. Established human Th1, Th2, and Th0 clones were stimulated with monocytes in a soluble CD3 mAb-mediated assay that is dependent on the presence of APC. Monocytes were exposed to low nonlethal doses of UVB radiation before coculture with T cells. UVB irradiation inhibited the capacity of monocytes to stimulate the proliferation and IFN-gamma production of Th1 cells in a dose-related fashion. In contrast, UVB-treated monocytes induced normal proliferation and IL-4 production in Th2 cells. Stimulation of Th0 cell proliferation by UVB-irradiated monocytes was normal, but a preferential suppression of IFN-gamma production was observed, thus leading to a more Th2-like cytokine response. The loss of Th1 proliferation upon stimulation with UVB-irradiated monocytes could be overcome by rIL-2; however, IFN-gamma production remained suppressed. IFN-gamma production could be completely restored by rIL-12, whereas the addition of IL-1 beta, TNF-alpha, or indomethacin had no such effect, nor did the addition of mAb to CD28, added to compensate for the reduced B7 expression of UVB-irradiated monocytes. Monocytes exposed to UVB radiation exhibited reduced expression of mRNA for the IL-1 2 subunits p35 and p40 and suppressed production of the IL-12 p70 protein. Our results thus indicate that UVB irradiation of APC selectively impairs Th1-like responses, a phenomenon caused by the UVB-induced suppression of monocyte IL-12 production.     

Regulation of T helper cell differentiation in vivo by soluble and membrane proteins provided by antigen-presenting cells

The aim of this study was to test whether the nature of the antigen-presenting cell (APC) can influence the Th1/Th2 balance in vivo. Our data show that dendritic cells (DC), pulsed extracorporeally with antigen, induced the development of cells secreting IL-2, IFN-gamma and IL-4 upon antigen rechallenge in vitro. Priming with peritoneal macrophages sensitized cells that produced IL-4 but not IFN-gamma. To identify the factors involved in T helper development, mice were primed with APC with or without treatment with neutralizing antibodies to costimulatory molecules or cytokines. Our results indicate that priming with DC or macrophages is strictly dependent on the CD28-CTLA4/B7 interaction. Of note, CD86 provides the initial signal to induce naive T cells to become IL-4 producers, whereas CD80 is a more neutral differentiation signal. IL-12, released by the DC, appears as a potent and obligatory inducer of differentiation for IFN-gamma-producing cells. IL-6, although produced by both APC populations, is necessary to direct activation of the Th2-type response by macrophages but not by DC.     

Regulation of monocyte IL-12 production: augmentation by lymphocyte contact and acute ethanol treatment, inhibition by elevated intracellular cAMP

IL-12, a monocyte-derived cytokine, is pivotal in activation of cellular immune response and inflammation. Both inflammatory response and cellular immunity are impaired by acute ethanol consumption. Here, we found that in vitro acute ethanol treatment (25-100 mM) results in a dose-dependent and significant increase of IL-12 in IFN-gamma (100 U/ml) plus Staphylococcal enterotoxin B (SEB; 1 microg/ml) stimulated monocytes and mononuclear cells but not in unstimulated cells from non-alcoholic blood donors. There was significantly greater IL-12 production in the MNC population compared to isolated Mphi (P < 0.001). Prevention of monocyte surface contact with either purified T lymphocytes or monocyte-depleted MNC resulted in a significant, 65+/-20%, decrease in IL-12 production regardless of IFN-gamma, SEB or ethanol stimulation suggesting that Mphi T-cell surface contact provides an additional signal for IL-12 production. In addition to cell surface contact, soluble mediators, particularly IL-10 and PGE2 may regulate IL-12 production. The cyclooxygenase inhibitor, Indomethacin (10(-6)M), augmented both IL-12 and IL-10 levels in isolated monocytes and mononuclear cells whether induced by medium, SEB or SEB plus 25 mM ethanol suggesting that regulation of IL-12 production via the cyclooxygenase pathway is independent of IL-10. Finally, elevation of intracellular cAMP levels by dbcAMP treatment consistently inhibited IL-12 as well as IL-10 production in monocytes induced by IFN-gamma or IFN-gamma plus 25 mM ethanol. These data suggest that augmentation of monocyte IL-12 by acute ethanol is not mediated via the cAMP pathway.     

Inhibition of IL-10 expression by IFN-gamma up-regulates transcription of TNF-alpha in human monocytes

Stimulation of human monocytes with LPS induces expression of multiple cytokines, including TNF-alpha, IL-1 beta, IL-6, and IL-10, IL-10 expression is delayed relative to that of TNF-alpha, IL-1 beta, and IL-6. Furthermore, IL-10 feedback inhibits expression of TNF-alpha, IL-1 beta, and IL-6, thus providing an efficient autocrine mechanism for controlling proinflammatory cytokine production in monocytes. The Th1-type lymphokine, IFN-gamma, markedly up-regulates TNF-alpha production in monocytes. However, the precise mechanism by which IFN-gamma mediates this effect is unknown. We examined the effects of IFN-gamma on IL-10 expression in LPS-stimulated monocytes, and the relationship between IL-10 and TNF-alpha production in these cells. LPS stimulation induced rapid, ordered expression of multiple cytokines. Steady-state mRNA levels for TNF-alpha increased rapidly, reached maximal levels by 2 to 3 h poststimulation, and then declined sharply. IL-1 beta and IL-6 mRNA levels also increased markedly following stimulation with LPS, but decreased more slowly than did TNF-alpha. Down-regulation of mRNA for TNF-alpha, IL-1 beta, and IL-6 coincided with a delayed and more gradual increase in IL-10 mRNA levels. Furthermore, neutralization of IL-10 with anti-IL-10 Abs prolonged TNF-alpha mRNA expression, and significantly increased net TNF-alpha production. IFN-gamma suppressed expression of IL-10 mRNA and protein in a dose-dependent manner. Moreover, inhibition of IL-10 production correlated with a marked increase in both the magnitude and duration of TNF-alpha expression. Thus, potentiation of TNF-alpha production by IFN-gamma in monocytes is coupled to inhibition of endogenous IL-10 expression.     

T cell-derived IL-4 and dendritic cell-derived IL-12 regulate the lymphokine-producing phenotype of alloantigen-primed naive human CD4 T cells

Previous studies on human Th subset development were restricted to the analysis of naive T cells activated with anti-CD3 mAb in the absence of physiologic APC. In this study, we have analyzed the role of cytokines and physiologic APC on T cell maturation in an Ag-specific system, in which naive neonatal CD4 T cells were primed with allogeneic dendritic cells (DC). We found that the cytokine profile of primed cells was dependent upon 1) the ratio between T cells and allogeneic DC and 2) the endogenous production of IL-4 and IL-12. Neutralization of IL-4 during primary MLR increased IFN-gamma production at priming and shifted the phenotype of primed cells from Th0 to Th1. These effects were IL-12 dependent, in that they were suppressed by anti-IL-12 Abs. The production of IL-12 in primary MLR was further evidenced by the presence of IL-12 p40 in the culture supernatant fluids. IL-12 production was suppressed by exogenous IL-4 and increased by anti-IL-4 blocking mAbs, indicating that endogenous IL-4 down-regulated IL-12 production by DC. Finally, IL-12 was produced as a result of T cell/DC interaction involving the CD40/CD40 ligand and CD28/B7 costimulation pathways, as revealed by the inhibitory effect of anti-CD40 ligand mAb and CTLA-4Ig. These observations suggest that in neutral conditions, Ag presentation by DC results in the coordinate production of naive T cell-derived IL-4 and DC-derived IL-12 that in concert shape the cytokine profile of Th cells.     

Phagocytosis of Leishmania mexicana amastigotes by macrophages leads to a sustained suppression of IL-12 production

Healing of leishmaniases is dependent on activation of parasitized macrophages (Mphi) by IFN-gamma, which is secreted by Leishmania-specific Th1 cells. IL-12 enhances IFN-gamma production by Th1 cells and is crucial for cure. The host cells of Leishmania sp., Mphi, are a main source of IL-12 in vivo. We report that infection of quiescent murine Mphi with L. mexicana or L. major amastigotes does not induce IL-12 production. Moreover, infection suppresses IL-12 secretion by Mphi activated by LPS, by CD40 cross-linking or cognate interaction with Th1 cells. IL-12 secretion is also suppressed in Mphi activated after phagocytosis of latex beads. Suppression is independent of engagement of CR3 or FcgammaR during phagocytosis, is not mediated by IL-10 and does not alter steady state IL-12p40 mRNA levels. In addition, suppression of IL-12 secretion does not depend on Mphi activation concurrent to infection. In contrast, NO production was not inhibited. Thus, Mphi effector functions are differentially affected and this may be a general effect of phagocytosis of non-activating particles. The possible implications of this effect on the infection are discussed.     

Modulation of endotoxin- and enterotoxin-induced cytokine release by in vivo treatment with beta-(1,6)-branched beta-(1,3)-glucan

Leukocytes activated by endotoxin or enterotoxins release proinflammatory cytokines, thereby contributing to the cascade of events leading to septic shock. In the present studies, we analyzed the effects of in vivo administration of a soluble immunomodulator, beta-(1,6)-branched beta-(1,3)-glucan (soluble beta-glucan), on toxin-stimulated cytokine production in monocytes and lymphocytes isolated from treated mice. In vitro stimulation of lymphocytes isolated from soluble beta-glucan-treated mice with lipopolysaccharide (LPS) resulted in enhanced production of interleukin-6 (IL-6) and suppressed production of tumor necrosis factor alpha (TNF-alpha), while stimulation of these cells with staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin 1 (TSST-1) resulted in enhanced production of gamma interferon (IFN-gamma) and suppressed production of IL-2 and TNF-alpha compared to that in cells isolated from untreated mice. In vitro stimulation of monocytes isolated from soluble beta-glucan-treated mice with LPS also resulted in suppressed TNF-alpha production, while stimulation of these cells with SEB or TSST-1 resulted in suppressed IL-6 and TNF-alpha production compared to that in cells isolated from untreated mice. Thus, the overall cytokine pattern of leukocytes from soluble beta-glucan-treated mice reflects suppressed production of proinflammatory cytokines, especially TNF-alpha. Taken together, our results suggest that treatment with soluble beta-glucan can modulate the induction cytokines during sepsis, resulting in an overall decrease in host mortality.     

Significance of platelet-derived endothelial cell growth factor in the angiogenesis of human gastric cancer

Most patients with primary IgA nephropathy (IgAN) have a significantly higher memory repertoire of IgA1-producing B lymphocytes in their bone marrow together with high plasma levels of IgA1. The connection between the mucosal immune system and the bone marrow compartment is probably based on traffic of either antigen-presenting cells (APC) or antigen-specific lymphocytes. Cytokines play an important role in the proliferation and differentiation of lymphoid cells. In order to mimic the in vivo situation as much as possible, we assessed cytokine production profiles ex vivo in 23 IgAN patients and matched controls, using lipopolysaccharide (LPS)- or phytohaemagglutinin (PHA)-stimulated whole blood (WB) cultures. Interferon-gamma (IFN-gamma), IL-2, IL-6, IL-10 and tumour necrosis factor-alpha (TNF-alpha) production in culture supernatants were determined by cytokine-specific ELISAs. Compared with controls, PHA-stimulated cultures resulted in significantly higher IL-10 (P<0.001), IL-2 (P<0.005) and IFN-gamma (P<0.001) levels in IgAN patients, but no significant differences in TNF-alpha or IL-6 levels were found. In LPS-stimulated cultures, the only significant difference (P<0.001) between the two groups was the increased IL-10 production in IgAN patients. The enhanced cytokine production in stimulated WB cultures suggests altered monocyte-related T cell responses in patients with IgAN. Increased IL-10 production may eventually result in an increased number of IgA-producing B lymphocytes in the bone marrow. In addition, high levels of endogenous IL-10 may down-regulate the effector functions of monocytes, or possibly APC in general, and consequently the IgA response at the mucosal level.     

Ligation of CD40 on dendritic cells triggers production of high levels of interleukin-12 and enhances T cell stimulatory capacity: T-T help via APC activation

We investigated the possibility that T helper cells might enhance the stimulatory function of dendritic cells (DCs). We found that ligation of CD40 by CD40L triggers the production of extremely high levels of bioactive IL-12. Other stimuli such as microbial agents, TNF-alpha or LPS are much less effective or not at all. In addition, CD40L is the most potent stimulus in upregulating the expression of ICAM-1, CD80, and CD86 molecules on DCs. These effects of CD40 ligation result in an increased capacity of DCs to trigger proliferative responses and IFN-gamma production by T cells. These findings reveal a new role for CD40-CD40L interaction in regulating DC function and are relevant to design therapeutic strategies using cultured DCs.     

Type I IFNs inhibit human dendritic cell IL-12 production and Th1 cell development

We have investigated the role of type I IFNs (IFN-alpha and -beta) in human T cell differentiation using anti-CD3 mAb and allogeneic, in vitro-derived dendritic cells (DC) as APCs. DC were very efficient activators of naive CD4+ T cells, providing necessary costimulation and soluble factors to support Th1 differentiation and expansion. Addition of IFN-alphabeta to DC/T cell cultures resulted in induction of T cell IL-10 production and inhibition of IFN-gamma, TNF-alpha, and LT secretion. Diminished T cell IFN-gamma production correlated with IFN-alphabeta-mediated inhibition of the p40 chain of the IL-12 heterodimer secreted by DC. Suppression of p40 IL-12 and IFN-gamma was not due to increased levels of IL-10 in these cultures, and production of IFN-gamma could be restored by exogenous IL-12. These data indicate that type I IFNs inhibit DC p40 IL-12 expression, which is required for development of IFN-gamma-producing CD4+ T cells. Furthermore, when T cells were restimulated without IFN-beta, these cells induced less p40 IL-12 from DC, suggesting that the functional properties of T cells may regulate DC function. Thus, IFN-alphabeta inhibits both IL-12-dependent and independent Th1 cytokine production and provides a mechanism for inhibition of IL-12-mediated immunity in viral infections.