Intensity of Fc-dependent phagocytosis of peritoneal macrophages and monocytes in peripheral blood in progeny of female rats with a chronic liver disorders]

The Fc-dependent phagocytosis of peritoneal macrophages and monocytes in the peripheral blood of the female rat progeny with a chronic autoimmune liver disease in the period of an early postnatal ontogenesis has been studied. The obtained results show a decrease of the Fc-dependent processes of macrophages. It is confirmed by a depression of the receptor expression, a decrease in the number of EA-rosettes, reduction of the macrophage affinity and inhibition of absorption of sensibilized erythrocytes.     

Enhancement of macrophage Fc-dependent phagocytosis by resident thymocytes: effect of a unique heat-stable lymphokine

Lymphocytes, activated by lectins or specific antigens, have been shown to enhance macrophage phagocytosis through the elaboration of a heat-labile soluble factor(s). Recent evidence from our laboratory revealed that resident (nonactivated) murine thymocytes and splenic lymphocytes increase peritoneal macrophage glucose metabolism through the elaboration of a heat-stable soluble factor(s). Therefore, we investigated the effect of resident lymphocyte subpopulations on macrophage Fc-dependent phagocytosis. Thioglycollate-elicited and resident peritoneal macrophages from BALB/c mice were cultured in serum-free media with syngeneic resident thymocytes or splenic T lymphocytes. Macrophage Fc-dependent phagocytosis was assayed by measuring the ingestion of 51CrSHEA. After 4 days in vitro, resident thymocytes produced a mean 160 (+/- 31) and 136% (+/- 22) increase in Fc-dependent phagocytosis by thioglycollate-elicited (thio-macrophages) and resident peritoneal macrophages, respectively. Splenic T lymphocytes increased thio-macrophage phagocytosis by 112% (+/- 41) under similar conditions. Macrophage Fc-dependent phagocytosis was increased after 24 hr of co-culture by supernatant derived from resident thymocytes and could be further enhanced by supernatant from Con A-activated thymocytes. Supernatant from guinea pig embryo fibroblasts did not increase macrophage phagocytosis. The soluble factor(s) was produced by resident thymocytes after 24 hr of preculture. This factor was active despite heating at 100 degrees C for 30 min whereas the effect of Con A-activated thymocyte supernatant was heat-labile. The stimulatory effect of resident thymocyte supernatant was not observed when the macrophages and supernatant were cultured in 2% FCS. In contrast to the factor(s) produced by resident thymocytes, the factor(s) in FCS that increased phagocytosis was heat-labile. These data suggest thymocytes and splenic T lymphocytes promote macrophage Fc-dependent phagocytosis in the absence of antigenic or lectin stimulation. This previously unrecognized effect of resident thymocytes is due to a unique heat-stable soluble factor(s) that is concealed in the presence of serum.     

A polyclonal model for B cell tolerance. I. Fc-dependent and Fc-independent induction of nonresponsiveness by pretreatment of normal splenic B cells with anti-Ig.

We have developed a simple and adaptable, polyclonal model for B cell nonresponsiveness that is based on the inhibitory activity of anti-Ig as a surrogate for Ag. In our system the induction phase (treatment with anti-Ig) is separated from the challenge phase (Ag or mitogen), so that the critical events in each phase can be evaluated. Our results show that T cell-depleted B cells precultured for 18 to 24 h with rabbit anti-Ig reagents are rendered unresponsive to challenge with either Ag, fluorescein coupled to Brucella abortus (FL-BA), or mitogen (LPS). This state of nonresponsiveness (anergy) is reflected by an inhibition of a prototype response to the fluorescein hapten, as well as total Ig and IgG synthesis, but no reduction in proliferation to LPS. Interestingly, mitogen-induced polyclonal antibody formation was consistently reduced by 90% by treatment with either F(ab')2 or intact IgG anti-Ig. In contrast, the Ag-driven (FL-BA) response of pretreated B cells was inhibited by only 50 to 70%. Moreover, the latter effect usually required pretreatment with intact IgG anti-Ig, a result that suggests the importance of an Fc-dependent negative signal affecting the B cell's response to FL-BA. Furthermore, pretreatment and coculture of B cells with IL-4 blocked the Fc-dependent inhibition of the FL-BA responsiveness. These results, as well as kinetics experiments establishing a 4-h latent period, suggest that simple blocking of surface Ig receptor on target B cells is not responsible for the induction of anergy. Pretreated B cells displayed unique phenotypic changes after treatment with anti-Ig, including a diminution of Thy-1 expression in response to LPS + IL-4, as well as a reduction in membrane IgM and J11d expression (i.e., they were IgMlo, IgDmed, and J11dlo, as recently reported for anergic B cells in transgenic mice). These results suggest that B cell anergy can be induced in mature B cells by both Fc-dependent and Fc-independent processes that lead to unique phenotypic changes and may reflect egress from G0 in the absence of T cell help. The significance of these changes to tolerance mechanisms is discussed.     

Effect of modified low density lipoproteins on humoral immune response and functional activity of macrophages in mice

Intravenous injection of acetylated low density lipoproteins (acLDL) in mice in a dose of 0.5 mg per mouse decreased the intensity of humoral immune response to sheep red blood cells (SRBC) by 35%. The addition of acLDL to mouse peritoneal macrophages in vitro resulted in inhibition of Fc-dependent phagocytosis of SRBC and fourfold increased secretion of prostaglandins E2 by macrophages. Fc-dependent phagocytosis of SRBC was also found to be inhibited by oxysterols (25-hydroxycholesterol and 7-ketocholesterol), added to the incubation medium of macrophages in vitro in doses of 0.5-5 mg/ml. The conclusion was made that oxidative metabolism of cholesterol and arachidonic acid, contained in LDL, may mediate the immunomodulating effects of modified LDL.     

Effect of lipopolysaccharide on the stimulation of macrophage Fc-dependent phagocytosis by splenic B lymphocytes

Macrophage phagocytic activity is regulated by a variety of products derived from activated lymphocytes. It has been reported that nonactivated splenic B and T lymphocytes enhance macrophage glucose metabolism. In addition, the enhancement of macrophage glucose metabolism was further increased by direct effects of bacterial lipopolysaccharide (LPS) on B, but not T, lymphocytes. In the present study, the effect of purified murine splenic B and T lymphocytes on Fc-dependent phagocytosis by thioglycollate-elicited peritoneal macrophages in the presence or absence of LPS has been investigated. Fc-dependent phagocytosis was assayed by measuring the ingestion of 51Cr-tagged sheep erythrocytes. After 3 or 4 days in culture, nonadherent spleen cells (NASC) and B and T lymphocytes from C3H/HeN (LPS-responder) mice produced 92 +/- 27%, 83 +/- 13%, and 147 +/- 33% increases in C3H/HeJ (LPS-hyporesponder) macrophage phagocytic activity, respectively. A similar effect was observed in Balb/c mice. Cell-free supernatant from NASC and B lymphocytes precultured for 2 or 4 days produced a 74 +/- 20% and 157 +/- 42% increase in phagocytosis respectively. At concentrations which have been previously shown to markedly enhance the ability of splenic B lymphocytes to stimulate macrophage glucose metabolism, Escherichia coli K235 LPS (10 micrograms/ml) did not alter the stimulatory effects of any of the splenic lymphocyte populations on macrophage Fc-dependent phagocytosis. These data suggest that B lymphocytes produce a soluble factor(s) which stimulates macrophage phagocytosis. In addition, LPS has different effects on the regulation of macrophage phagocytic activity and metabolism by B lymphocytes.     

Gangliosides block the inhibition of macrophage Fc-dependent phagocytosis by lipopolysaccharide

The mechanism whereby bacterial lipopolysaccharide (LPS) exerts its biologic effects on mammalian cells is unknown. Plasma membrane gangliosides bind bacterial toxins and have been implicated in modulating the effects of a variety of immunoregulatory substances. We investigated the possibility that gangliosides can inhibit the effect of lipopolysaccharide on Fc-dependent phagocytosis by murine peritoneal macrophages. Protein-free lipopolysaccharide preparations significantly inhibited Fc-mediated phagocytosis (less than 71% of control) at concentrations of 100 ng/ml or greater after 90 min of incubation. The inhibitory effect of LPS (1 micrograms/ml) was blocked when macrophages were incubated with mono-, di-, or trisialogangliosides (25-50 micrograms/ml). Neither asialoganglioside nor sialic acid alone were capable of blocking the effect of LPS. When chromatographed separately on a Sepharose 4B column, LPS and trisialoganglioside had different elution profiles. LPS and trisialoganglioside coeluted, however, when premixed at 37 degrees C for 60 min and then applied to the column. Therefore, abrogation of the effect of LPS on Fc-dependent phagocytosis may occur as a consequence of direct interaction between LPS and gangliosides. These data suggest that gangliosides may modulate the response of macrophages to bacterial lipopolysaccharide.     

Effect of astasilid on the stimulation of peritoneal macrophages

The effect of astasilid, a sucrose monoester and the effect of mainly unsaturated fatty acids from the lipid fraction of Astasia longa on immunocompetent cells--macrophages of the mouse peritoneal cavity were studied. It was shown that astasilid increased 7.5-8.5-fold expression of Fc-receptors on the macrophage plasmic membranes and stimulated 5.5-6.5-fold the macrophage capacity for Fc-dependent phagocytosis of sheep red blood cells. Astasilid had no effect on migration of the macrophages into the abdominal cavity.     

Induction of nonspecific cytotoxicity by monoclonal anti-T3 antibodies

The effects of monoclonal anti-T3 antibodies on the effector phase of cytotoxic T lymphocytes (CTL) were studied with respect to antigen-specific and antigen-nonspecific lysis of different target cells. Anti-T3 antibodies inhibited the antigen-specific lysis by CTL generated in mixed lymphocyte cultures (MLC), but they concomitantly augmented the nonspecific killing of third-party cells such as the cell lines Daudi, Raji, and K562. This nonspecific cytotoxicity was induced by various anti-T3 antibodies, whereas antibodies reactive with other antigens expressed on the cytotoxic effector cells lacked any such activity. Anti-T3 antibodies induced nonspecific cytotoxicity only when activated T cells, obtained by primary MLC, by repeated restimulation, or after cloning, were used. The antibodies had no effect on unstimulated peripheral T lymphocytes or thymocytes. The inhibition of the antigen-specific lysis and the induction of nonspecific lysis by anti-T3 was dose dependent, and both effects occurred at the same concentration range of anti-T3. F(ab')2 fragments of anti-T3 inhibited the specific lysis but were not able to induce cytotoxic activity, indicating that this induction is an Fc-dependent process. When different target cells were tested, only Fc receptor-positive cells were susceptible for this nonspecific cytotoxicity. Thus, anti-T3 antibodies have a dual effect on effector CTL: they inhibit antigen-specific lysis and concomitantly induce nonspecific lysis in an Fc-dependent way.     

Molecular and functional characterization of cynomolgus monkey IgG subclasses

Studies for vaccine and human therapeutic Ab development in cynomolgus monkeys (cynos) are influenced by immune responses, with Ab responses playing a significant role in efficacy and immunogenicity. Understanding the nature of cyno humoral immune responses and characterizing the predominant cyno IgG types produced and the Fc-FcγR interactions could provide insight into the immunomodulatory effects of vaccines. Anti-drug Ab responses against human IgG therapeutic candidates in cynos may affect efficacy and safety assessments because of the formation of immune complexes. There is, however, limited information on the structure and function of cyno IgG subclasses and how they compare with human IgG subclasses in Fc-dependent effector functions. To analyze the functional nature of cyno IgG subclasses, we cloned four cyno IgG C regions by using their sequence similarity to other primate IgGs. The four clones, cyno (cy)IGG1, cyIGG2, cyIGG3, cyIGG4, were then used to construct chimeric Abs. The sequence features of cyno IgG subclasses were compared with those of rhesus monkey and human IgG. Our data show that rhesus monkey and cyno IgG C regions are generally highly conserved, with differences in the hinge and hinge-proximal CH2 regions. Fc-dependent effector functions of cyno IgG subclasses were assessed in vitro with a variety of binding and functional assays. Our findings demonstrate distinctive functional properties of cyno IgG subclasses. It is notable that human IgG1 was less potent than cyno IgG1 in cyno FcγR binding and effector functions, with the differences emphasizing the need to carefully interpret preclinical data obtained with human IgG1 therapeutics.     

Colony-forming ability of ataxia-telangiectasia skin fibroblasts is an indicator of their early senescence and increased demand for growth factors

Homogenate transglutaminase (TGase)-specific activity of guinea pig peritoneal macrophages was measured under a variety of conditions that stimulate or activate macrophages. Resident peritoneal macrophages had low levels of TGase as compared with oil-elicited inflammatory macrophages, which showed 30- to 100-fold greater enzyme activity. Immunofluorescent staining with specific antibody to purified enzyme showed a corresponding increase in staining intensity in subpopulations of inflammatory macrophages. Stimulation of macrophages with bacterial endotoxin, lymphokine, or Lotus tetragonolobus lectin resulted in increased TGase-specific activity. Cystamine, an inhibitor of the enzyme, reduced TGase activity, reduced lymphokine-mediated migration inhibition, and inhibited Fc-mediated phagocytosis. The substrate inhibitors, methylamine and dansylcadaverine, also inhibited Fc-dependent phagocytosis. These results suggest a possible role for TGase in macrophage activation and in receptor-dependent phagocytosis.     

Human monocyte chemiluminescence triggered by IgG aggregates. Requirement of phospholipase activation and modulation by Fc receptor ligands

Human mononuclear cells stimulated with soluble IgG aggregates generated chemiluminescence, a response attributable to monocytes. Some requirements of this reaction were examined by preincubation of the cells with a variety of inhibitors. The protease antagonists TPCK and TLCK, the phospholipase inhibitors quinacrine and BPB, and the calcium channel blocker verapamil were all inhibitory at micromolar concentrations. The oxygen metabolite scavengers SOD and catalase were less inhibitory. These findings are consistent with a major role for arachidonic acid metabolites in the generation of light. Modulation of monocyte Fc-mediated chemiluminescence also occurred by preincubation of the cells with Fc ligands. While IgG aggregates and monomeric IgG blocked Fc-dependent chemiluminescence, IgG Fc fragments were stimulatory of this response.     

Requirement for Fc Effector Mechanisms in the APOBEC3/Rfv3-Dependent Neutralizing Antibody Response

Antiretroviral neutralizing antibody (NAb) responses are often evaluated in the absence of Fc-dependent immune effectors. In murine Friend retrovirus infection, Apobec3/Rfv3 promotes a potent polyclonal NAb response. Here, we show that the Apobec3/Rfv3-dependent NAb response correlated with virus-specific IgG2 titers and that the in vivo neutralization potency of Apobec3/Rfv3-resistant antisera was dependent on activating Fcγ receptors but not complement. The data strengthen retroviral vaccine strategies aimed at eliciting NAbs that activate specific Fcγ receptors.     

Indomethacin modulation of Adriamycin-induced effects on multiple cytolytic effector functions

Summary The anticancer agent, Adriamycin (ADM), in addition to being a potent cytotoxic drug has been shown to be an effective immunomodulator. This study was undertaken to determine whether ADM-induced changes in the production of prostaglandins (particularly PGE₂) are involved in ADM-associated modifications of selected host defenses. Spleen cells from normal or ADM-treated (5 mg/kg; day –5) C57BL/6 mice were assessed for the following activities: fresh (day 0) and cultured natural killer (NK), cytotoxic T lymphocyte, lymphokine-activated killer (LAK), Fc-dependent phagocytosis and tumoricidal macrophage. All activities were assessed with and without the addition of indomethacin, an inhibitor of the first step of the cyclo-oxygenase pathway of prostaglandin synthesis. Depending on culture conditions, the cytotoxic T lymphocyte and splenic tumoricidal macrophage activities were either unaffected or were augmented by ADM treatment of the spleen donor mice or by addition of indomethacin to the culture, and these effects were apparently independent of one another. In contrast, ADM treatment generally resulted in reduced NK and LAK activities relative to control and elevated Fc-dependent phagocytosis. The addition of indomethacin to the culture effectively reversed these effects. Furthermore, spleen cells from ADM-treated mice were found to produce twice the amount of PGE₂ in culture compared to cells from untreated mice. Finally, the direct addition of PGE₂ to NK cultures resulted in a dose-dependent inhibition of NK activity and the dose required was comparable to the amount of PGE₂ produced by cultured spleen cells from ADM-treated mice. Taken together, these results indicate that at least some of the immunomodulatory effects of ADM are an indirect result of ADM-induced changes in PGE₂ production.This work was supported in part by USPHS grants CA-28 835, CA-15 142, CA-24 538 and CA-09072 and from Veterans Administration Research Funds     

Interactions of oxidative stress with thiamine homeostasis promote neurodegeneration

Thiamine-dependent processes are diminished in brains of patients with several neurodegenerative diseases. The decline in thiamine-dependent enzymes can be readily linked to the symptoms and pathology of the disorders. Why the reductions in thiamine linked processes occur is an important experimental and clinical question. Oxidative stress (i.e. abnormal metabolism of free radicals) accompanies neurodegeneration and causes abnormalities in thiamine-dependent processes. The vulnerability of thiamine homeostasis to oxidative stress may explain deficits in thiamine homeostasis in numerous neurological disorders. The interactions of thiamine with oxidative processes may be part of a spiral of events that lead to neurodegeneration, because reductions in thiamine and thiamine-dependent processes promote neurodegeneration and cause oxidative stress. The reversal of the effects of thiamine deficiency by antioxidants, and amelioration of other forms of oxidative stress by thiamine, suggest that thiamine may act as a site-directed antioxidant. The data indicate that the interactions of thiamine-dependent processes with oxidative stress are critical in neurodegenerative processes.     

Fc-dependent inhibition of mouse B cell activation by whole anti-mu antibodies

We have been using whole rabbit anti-mouse mu antibodies to study Fc-dependent inhibition of mouse B cell activation by F(ab')2 anti-mu antibodies and antigen-nonspecific helper factors (SN). We show here that this inhibition does not appear to require adherent cells, appears to occur independently of cellular interactions, is reversible, and is not maintained solely by suppressive factors. In addition, occupancy of Fc receptors by rabbit antibody-antigen complexes is not sufficient to inhibit activation by F(ab')2 anti-mu and SN. These observations, in conjunction with the observation that blocking the Fc receptor-binding capacity of rabbit anti-mu antibodies by protein A prevents inhibition, suggest that cross-linking mlg and Fcgamma receptors on B cells prevents activation. However, the F(ab')2 anti-mu and SN-activated B cells become refractory to this inhibition by 48 hr in culture.     

Effects of salt stress on basic processes of photosynthesis

Salt stress causes decrease in plant growth and productivity by disrupting physiological processes, especially photosynthesis. The accumulation of intracellular sodium ions at salt stress changes the ratio of K : Na, which seems to affect the bioenergetic processes of photosynthesis. Both multiple inhibitory effects of salt stress on photosynthesis and possible salt stress tolerance mechanisms in cyanobacteria and plants are reviewed.     

Role of Fc gamma RII in platelet activation by monoclonal antibodies.

mAb are being widely used to probe the function of cell-surface proteins. The cell stimulation that may be produced is often dependent on mAb interaction with both the target Ag and FcR. However, it remains unclear whether these interactions take place on the same cell or between adjacent cells and whether the FcR plays an anchoring or signaling role. Using the model of platelet activation, we demonstrate that two different Fc-dependent mAb, LeoA1 and ALB6, both activate the cell by forming intercellular links between Ag on one cell and FcR on the opposing platelet. We also show that the mAb differ with respect to the relative roles of target Ag vs FcR in provision of the stimulation signal. Thus Fc gamma RII played a mainly anchorage role in LeoA1 stimulation, whereas its role in ALB6 stimulation was mainly signaling. Therefore the precise contribution of each of these roles to the overall effect of a stimulatory antibody should be determined before the antibody is used as a specific functional probe.     

Effects of salt stress on basic processes of photosynthesis

Salt stress causes decrease in plant growth and productivity by disrupting physiological processes, especially photosynthesis. The accumulation of intracellular sodium ions at salt stress changes the ratio of K : Na, which seems to affect the bioenergetic processes of photosynthesis. Both multiple inhibitory effects of salt stress on photosynthesis and possible salt stress tolerance mechanisms in cyanobacteria and plants are reviewed.This revised version was published online in March 2005 with corrections to the page numbers.     

非生物胁迫影响水稻颖花育性机理的研究进展

本文从颖花发育的形态学和生理学角度,综述了水稻穗分化期至抽穗开花期非生物胁迫导致颖花不育的机理,旨在揭示非生物胁迫导致水稻颖花败育的关键过程及其内在联系.颖花是否可育主要与绒毡层细胞行为、花药开裂与散粉、花粉萌发、受精4个关键过程有关,胁迫通过影响这些关键过程,导致颖花不育.花药发育早期异常变化影响生殖细胞发育与授粉作用.可以通过喷施外源物质或增施硅肥等方法减缓非生物胁迫对颖花育性的伤害.今后需要加强交叉胁迫对颖花育性的影响、不同胁迫对花器官形态结构和生理特性的影响、不同水稻品种对胁迫的响应差异,以及胁迫影响花器官发育的分子生物学机制等方面的研究.     

Cell identity regulators link development and stress responses in the Arabidopsis root

Stress responses in plants are tightly coordinated with developmental processes, but interaction of these pathways is poorly understood. We used genome-wide assays at high spatiotemporal resolution to understand the processes that link development and stress in the Arabidopsis root. Our meta-analysis finds little evidence for a universal stress response. However, common stress responses appear to exist with many showing cell type specificity. Common stress responses may be mediated by cell identity regulators because mutations in these genes resulted in altered responses to stress. Evidence for a direct role for cell identity regulators came from genome-wide binding profiling of the key regulator SCARECROW, which showed binding to regulatory regions of stress-responsive genes. Coexpression in response to stress was used to identify genes involved in specific developmental processes. These results reveal surprising linkages between stress and development at cellular resolution, and show the power of multiple genome-wide data sets to elucidate biological processes.