Effects of dietary protein type on oxidized cholesterol-induced alteration in age-related modulation of lipid metabolism and indices of immune function in rats

Exogenous oxidized cholesterol disturbs both lipid metabolism and immune functions. Therefore, it may perturb these modulations with ageing. Effects of the dietary protein type on oxidized cholesterol-induced modulations of age-related changes in lipid metabolism and immune function was examined using differently aged (4 weeks versus 8 months) male Sprague-Dawley rats when casein, soybean protein or milk whey protein isolate (WPI) was the dietary protein source, respectively. The rats were given one of the three proteins in diet containing 0.2% oxidized cholesterols mixture. Soybean protein, as compared with the other two proteins, significantly lowered both the serum thiobarbituric acid reactive substances value and cholesterol, whereas it elevated the ratio of high density lipoprotein-cholesterol/cholesterol in young rats, but not in adult. Moreover, soybean protein, but not casein and WPI, suppressed the elevation of Delta6 desaturation indices of phospholipids in both liver and spleen, particularly in young. On the other hand, WPI, compared to the other two proteins, inhibited the leukotriene B4 production of spleen, irrespective of age. Soybean protein reduced the ratio of CD4(+)/CD8(+) T-cells in splenic lymphocytes. Therefore, the levels of immunoglobulin (Ig)A, IgE and IgG in serum were lowered in rats given soybean protein in both age groups except for IgA in adult, although these observations were not shown in rats given other proteins. Thus, various perturbations of lipid metabolism and immune function caused by oxidized cholesterol were modified depending on the type of dietary protein. The moderation by soybean protein on the change of lipid metabolism seems to be susceptible in young rats whose homeostatic ability is immature. These observations may be exerted through both the promotion of oxidized cholesterol excretion to feces and the change of hormonal release, while WPI may suppress the disturbance of immune function by oxidized cholesterol in both ages. This alleviation may be associated with a large amount of lactoglobulin in WPI. These results thus showed a possibility that oxidized cholesterol-induced perturbations of age-related changes of lipid metabolism and immune function can be moderated by both the selection and combination of dietary protein.     

Stimulation of immunoglobulin biosynthesis in human B cells by wheat germ agglutinin. I. Evidence that WGA can produce both a positive and negative signal for activation of human lymphocytes

Wheat germ agglutinin (WGA), previously regarded strictly as a nonmitogenic or anti-mitogenic lectin, can under appropriate conditions markedly stimulate in vitro synthesis and secretion of immunoglobulin (Ig) by human B lymphocytes. Stimulation of Ig production by WGA is 1) confined to a narrow lectin dose range (2 to 10 micrograms/ml; 2) abrogated by the simple sugar N-acetyl-D-glucosamine but not by a variety of other monosaccharides; 3) effective only after early additions of WGA within the initial 72 hr of 12-day cultures; 4) detected in the presence of B and T cells but not B cells alone; and 5) polyisotypic in nature, as indicated by augmented synthetic rates of Ig in each of 3 major classes (IgG, IgA, and IgM). With few exceptions, WGA produces equivalent or greater rates of Ig production as obtained in cultures activated with pokeweed mitogen (PWM), a well-recognized T-dependent polyclonal activator of human B cells. Furthermore, periperal blood lymphocytes from select individuals that respond weakly to PWM are markedly stimulated with WGA. In contrast to these stimulatory effects of WGA on Ig production by lymphocytes exposed to low lectin concentrations, addition of WGA in amounts greater than 15 micrograms/ml to PWM-stimulated human lymphocyte cultures produces marked suppression of the expected level of Ig synthesis. These data indicate that varying doses of WGA can produce contrasting stimulatory and inhibitory effects on human B cell metabolism.     

Oxidative stress by visible light irradiation suppresses immunoglobulin production in mouse spleen lymphocytes

In this study, we attempted to induce the oxidative stress in mouse spleen lymphocytes with visible light irradiation and examined the effects of lipid peroxidation on immunoglobulin (Ig) production. The spleen lymphocytes were isolated from 8-week-old male balb/c mice and irradiated with 300 W visible light. When the cells were cultured for 72 hr, Ig contents in culture supernatants were decreased gradually by irradiation for over 30 min. The cell viability was also lowered by the irradiation. Intracellular phosphatidylcholine hydroperoxide (PCOOH) levels and thiobarbituric acid-reactive substances (TBARS) values in culture supernatants were measured as indices of lipid peroxidation and we found that Ig production by mouse spleen lymphocytes was suppressed accompanied with the progress of peroxidation of intracellular phospholipids. Cell membrane fluidity was also significantly decreased, but the intracellular Ig level was not changed in the irradiated cells. These results suggest that the peroxidation of intracellular lipids is a cause of the suppression of Ig production by mouse spleen lymphocytes via lowering cell viability and suppressing Ig synthesis and secretion.     

Local production of IgG4 in human colostrum

Total IgG4 levels were determined in 27 colostrum and 27 plasma paired samples by using RIA techniques, and total IgG was determined on the same pairs by using radial immunodiffusion. In colostrum, the mean IgG4 level was 4.6 micrograms/ml (0.6 to 19.0), and in the plasma the mean IgG4 level was 170.5 micrograms/ml (30 to 920). IgG averaged 42.3 micrograms/ml (12 to 240) in colostrum and 7980.9 micrograms/ml (3250 to 16,000) in plasma. Of colostral IgG, 15.3% was IgG4, whereas only 3.5% of plasma IgG was IgG4. Specific IgG4 antibodies to beta-lactoglobulin, bovine serum albumin, bermuda grass, and alpha-gliadin were also assayed. In six patients, strong evidence was found for local mammary production of IgG4-specific antibodies.     

Dietary effect of guar gum and its partially hydrolyzed product on the lipid metabolism and immune function of Sprague-Dawley rats

The dietary effect of the water-soluble dietary fibers (WSDF), guar gum, partially hydrolyzed guar gum (PHGG), glucomannan, highly methoxylated (HM) pectin, on the serum lipid level and immunoglobulin (Ig) production of Sprague-Dawley rats was compared with that of water-insoluble cellulose. Although serum total cholesterol and triglyceride levels were significantly lower in the rats fed with WSDF than in those fed with cellulose, a decrease in the level of phospholipids was only observed in the rats that had been fed on guar gum or glucomannan. In addition, all WSDF feeding enhanced IgA productivity in the spleen and mesenteric lymph node lymphocytes, although the increase in serum IgA level was only observed in the rats fed on WSDF, and not on PHGG. When mesenteric lymph node lymphocytes were cultured in the presence of various concentrations of guar gum or glucomannan, no significant increase in Ig production was apparent. These data suggest that WSDF indirectly enhanced the Ig production of lymphocytes, and that serum lipid reduction and IgA production-enhancing activities of WSDF were dependent on their molecular sizes.     

第三脑室注射组胺及其受体激动剂对五肽促胃液素诱导...

The present study shows the dual effects of intraventricularly injected histamine (0.25-2.0 micrograms/5 microliters) on pentagastrin-induced gastric acid secretion. Male Wistar rats weighing 200-300 g were anesthetized with intraperitoneal sodium pentobarbital. Gastric acid was continuously washed out with 37 degrees C saline solution by means of a perfusion pump. On the background of continuous intravenous infusion of pentagastrin [7.5 micrograms/(kg.h),] histamine (0.25 microgram/5 microliters) or 2-pyridylethylamine (PEA, 10 micrograms/5 microliters), a H1-receptor agonist, was injected into the third ventricle through a chronically implanted canula. The acid output decreased 10 min after injection and did not recover at 90 min. When the dose of histamine was increased to 1.0 micrograms or 2.0 micrograms, dual effects appeared. The acid output decreased respectively in 73% or 50% of the animals, while in the rest 27% and 50% of the animals, the acid output increased. H2-receptor agonist dimaprit (10 micrograms/5 microliters, i.c.v.) or impromidine (0.1 micrograms/5 microliters, i.c.v.) had no pronounced effect on pentagastrin-induced acid secretion. Pretreatment with diphenhydramine (16 micrograms/0.2 ml or 32 micrograms/0.2 ml, i.m.) abolished the inhibitory effect of histamine and PEA on acid secretion. These results suggest that histamine may be involved in the central regulation of gastric acid secretion, and the inhibitory effect may be mediated by H1-receptors in the brain. The mechanism underlying the production of the dual effects of histamine is unknown.     

Host immune responses to tumor cells augmented by bleomycin and their therapeutic effects on rat fibrosarcoma

The administration--timing-dependent therapeutic effects of bleomycin (BLM) were observed on a fibrosarcoma implanted SC in WKA rats. Five consecutive IP administrations of BLM (5 mg/kg/d) were found to be more effective when BLM was given from Day 8 than when it was given from Day 1 for tumors implanted on Day 0. The therapeutic effects correlated well with antitumor immune responses, which were examined on Day 13 when the tumor had not yet regressed even in surviving rats. The tumor-neutralizing activity of spleen cells was augmented in rats treated with BLM from Day 8 to Day 12, and the suppressor cell activity detected in the spleen cells of tumor-bearing rats was eliminated by the BLM treatment. The tumoricidal activity of peritoneal exudate cells (PEC) was detected in rats treated from Day 8 but not in rats untreated or treated from Day 1. The in vitro treatment of KMT-17 cells with BLM (20 micrograms/ml) for two hours enhanced the sensitivity of the tumor cells to the activity of tumoricidal PEC. This suggests that the direct action of BLM on tumor cells also plays an immunologic role in BLM treatment. The findings reveal that the therapeutic effect of BLM is elicited by its ability to augment the host immune responses to tumor cells.     

Oxidized LDL increase free cholesterol and fail to stimulate cholesterol esterification in murine macrophages

Oxidatively modified low density lipoproteins (Ox-LDL) may be involved in determining the formation of foam cells by inducing cellular cholesteryl ester accumulation. We studied the effect of copper oxidized LDL (Ox-LDL) on cholesterol accumulation and esterification in murine macrophages. Ox-LDL (44 micrograms/ml of lipoprotein cholesterol) increased the total cholesterol content of the cells from 29 to 69 micrograms/mg cell protein. Free cholesterol accounted for 85% of this increase. Acetyl LDL (Ac-LDL) (38 micrograms/ml of lipoprotein cholesterol), raised total cellular cholesterol content to a similar extent (76 micrograms/mg cell protein), however only 25% of the accumulated cholesterol was unesterified. When ACAT activity was determined after incubation of J774 cell with Ox- or Ac-LDL, Ox-LDL were 12 times less effective than Ac-LDL in stimulating cholesteryl ester formation. This was not due to an inhibition of ACAT by Ox-LDL since these lipoproteins failed to inhibit pre activated enzyme in cholesteryl ester-loaded macrophages. The uptake of 125I-Ox-LDL: was 175% that of 125I-Ac-LDL, while degradation was only 20%. All together these data suggest an altered intracellular processing of Ox-LDL, which may be responsible for free cholesterol accumulation.     

7-ketocholesterol inhibits VLDL secretion by cultured human and rabbit hepatocytes

7-ketocholesterol, one of the major product of autoxidation of dietary cholesterol, was found to inhibit secretion of very low density lipoprotein [14C]cholesterol, [14C]triacylglycerol and [35S]apoprotein B,E,C by cultured human and rabbit hepatocytes. A parallel inhibition (about 35%) of cholesterol synthesis but not of triacylglycerol formation was observed. Incubation with 10 micrograms/ml of oxysterol also reduced the total apo-B secretion measured by ELISA and increased intracellular apo-B mRNA level. These results seem to indicate that 7-ketocholesterol decreases secretion of very low density lipoprotein (VLDL) particles and exerts inhibitory effects on apo-B production at the co-translational or posttranslational level.     

Action of diethylcarbamazine citrate on protective immunity in rats infected with Nippostrongylus brasiliensis

Rats made immune to Nippostrongylus brasiliensis and treated with diethylcarbamazine citrate (DEC) orally (250 mg/kg X 6) exhibited significant suppression of functional immunity. Similarly, administration of compound 48/80 (100 micrograms/rat i.p.) made the immune rats susceptible to challenge infection. Treatment of rats, with 22-day infection with compound 48/80, histamine (20 mg/rat, per os), or L-histidine (20 mg/rat, orally s.c.) did not accelerate worm expulsion. A massive complement-dependent adherence of peritoneal cells (1 X 10(8], isolated from immune DEC-treated and untreated rats, to infective larvae (L3) was observed. Likewise, heavy congregation of normal peritoneal cells to larvae was noticed when the cells were incubated with sera obtained from immune, DEC-treated or untreated rats. The rats receiving mesenteric lymph node cells (125 X 10(6) i.v.) or sera (0.5 ml or 1 ml X 3 i.p.), obtained from immune DEC-treated rats and challenged with infective larvae developed 50% more worms than those which received cells or serum from untreated immune donors. DEC appears to cause suppression of functional immunity and worm expulsion is not histamine mediated.     

Ascaris suum: human lymphocyte mitogenic factor content

Ascaris suum extract was found to contain a mitogenic factor which stimulates human lymphocytes. The extract (100 micrograms protein/ml) induced an increase in [3H]thymidine incorporation into human lymphocytes at a level similar to that obtained with pokeweed mitogen (11 micrograms/ml). Stimulation of mitosis appeared to be more effective with T lymphocytes than non-T lymphocytes. The mitogenic activity of the extract was reduced by only 27% when treated at 56 C for 30 min or when immersed into boiling water for 1 min. The extract was fractionated into four protein peaks by Sephacryl S-200 column chromatography. Lymphocyte mitogenic activity was observed in the first half of the first protein peak. Allergenic activity, assessed by the passive cutaneous anaphylaxis test in rats, was observed in the latter half of the same peak. These results suggest that A. suum contains both an allergen and a mitogenic substance.     

Combined effects of desialylated and glycosylated low density lipoproteins on lipid content of human aortic intima cells in vitro]

We have studied a combined effect of glycosylated low density lipoproteins (LDL) on the cholesterol content of cells cultured from unaffected human aortic intima. Native LDL did not alter the intracellular cholesterol level while glycosylated LDL taken in the concentration of 50 and 100 mg/ml increased the cell cholesterol content by 30 and 70 percent, respectively. The effect of the same concentrations of glycosylated LDL treated with neuraminidase (desialylated-glycosylated LDL) was twice as powerful. Desialylated LDL in the concentration of 50 and 100 mg/ml raised the cholesterol level by 1.4- and 2.1-fold, respectively. Simultaneous incubation of cells with glycosylated (50 mg/ml) and desialylated (50 mg/ml) LDL brought about a 3.4-fold increase in intracellular cholesterol. The obtained data suggest that intensive development of atherosclerosis in diabetes mellitus may be partially explained by synergic effects of desialylated and glycosylated lipoproteins as well as LDL with both types of modification.     

Low density lipoprotein (LDL) inhibits histamine release from human mast cells

We examined the effect of low density lipoprotein (LDL) on histamine release from purified human lung mast cells. LDL inhibited anti-IgE- induced histamine release in a dose-dependent manner, with 100 micrograms/ml LDL-protein inhibiting histamine release by 53 +/- 8% (mean +/- SEM); half-maximal inhibition occurred at 40-80 micrograms/ml. LDL also inhibited calcium ionophore A23187-induced histamine release in a dose-dependent manner, with 1 mg/ml of LDL inhibiting histamine release by 83 +/- 9%; half maximal inhibition occurred at 220-280 micrograms/ml. Inhibition by LDL was time-dependent: half-maximal inhibition of anti-IgE- induced histamine release by LDL occurred at 30-50 minutes of incubation. The inhibitory effect of LDL was independent of buffer calcium concentrations (0-5 mM) or temperature (0-37 degrees C). These data are consistent with a newly defined immunoregulatory role for LDL.     

Urinary N tau-methylimidazole acetic acid excretion in respiratory disease

N tau-methylimidazole acetic acid (N tau-MIAA) is the principal urinary metabolite of histamine. The basal urinary excretion rate of N tau-MIAA was determined as 0.117 +/- 0.008 (SE) mg/h, with a renal clearance for N tau-MIAA of 273 +/- 27 ml/min implying active secretion. After subpharmacological infusion of histamine (50 ng.kg-1.min-1 over 2 h) in five volunteers that increased plasma histamine from 0.28 +/- 0.04 to 0.71 +/- 0.15 ng/ml, urinary excretion of N tau-MIAA over 8 h was increased by less than 17% compared with a control saline infusion. Urinary N tau-MIAA excretion in normal controls (273 +/- 14 micrograms/mmol creatinine) was similar to that observed in patients with severe acute asthma (253 +/- 22 micrograms/mmol), antigen-induced bronchoconstriction (269 +/- 21 micrograms/mmol), seasonal allergic rhinitis (304 +/- 31 micrograms/mmol), and clinically stable bronchiectasis (270 +/- 22 micrograms/mmol). In contrast, large increases in metabolite excretion (greater than 7,000 micrograms/mmol creatinine) were observed in a patient with systemic mastocytosis where very high plasma histamine levels were recorded (greater than 500 ng/ml) and marked systemic hemodynamic effects occurred. We conclude that urinary N tau-MIAA will only be increased in pathologies where sustained hyperhistaminemia occurs and that increased local histamine production in the lung or the upper airway does not cause a measurable change in the basal urinary excretion of this metabolite.     

The human recombinant c-kit receptor ligand, rhSCF, induces mediator release from human cutaneous mast cells and enhances IgE-dependent mediator release from both skin mast cells and peripheral blood basophils.

The gene product of the steel locus of the mouse represents a growth factor for murine mast cells and a ligand for the c-kit proto-oncogene receptor, a member of the tyrosine kinase receptor class of oncogenes (for review, see O. N. Witte. 1990. Cell 63:5). We have studied the effect of the human recombinant c-kit receptor ligand stem cell factor (rhSCF) on the release of inflammatory mediators from human skin mast cells and peripheral blood basophils and compared its activity to that of rhIL-3, rhSCF (1 ng/ml to 1 microgram/ml) activated the release of histamine and PGD2 from mast cells isolated from human skin. Analysis by digital video microscopy indicated that purified human skin mast cells (84 +/- 5% pure) responded to rhSCF (0.1 to 1 microgram/ml) challenge with a rapid, sustained rise in intracellular Ca2+ levels that was accompanied by secretion of histamine. A brief preincubation (10 min) of mast cells with rhSCF (0.1 pg/ml to 1 ng/ml) significantly enhanced (100 +/- 35%) the release of histamine induced by anti-IgE (3 micrograms/ml), but was much less effective on IgE-mediated release of PGD2. In contrast, a short term incubation with rhSCF did not potentiate the secretion of histamine activated by substance P (5 microM). A 24-h incubation of mast cells with rhSCF did not affect the release of mediators induced by anti-IgE (3 micrograms/ml), probably due to receptor desensitization, rhSCF (1 ng/ml to 3 micrograms/ml) neither caused release of histamine or leukotriene C4 (LTC4) release from leukocytes of 14 donors, nor induced a rise in intracellular Ca2+ levels in purified (greater than 70%) basophils. Brief preincubation (10 min) of leukocytes with rhSCF (1 ng/ml to 3 micrograms/ml) caused an enhancement (69 +/- 11%) of anti-IgE-induced release of histamine that was significant at concentrations as low as 3 ng/ml (p less than 0.05), whereas it appeared less effective in potentiating IgE-mediated LTC4 release. In contrast, a prolonged incubation (24 h) with rhSCF (0.1 pg/ml to 100 ng/ml) did not enhance the release of histamine or LTC4 induced by anti-IgE (0.1 microgram/ml), whereas rhIL-3 (3 ng/ml) significantly potentiated the release of both mediators.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dietary effects of eicosapentaenoic and docosahexaenoic acid esters on lipid metabolism and immune parameters in Sprague-Dawley rats

Sprague-Dawley rats were fed eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) ethyl esters at the 2% level for 3 weeks to clarify their effects on immune functions. In the rats fed EPA or DHA, serum cholesterol, triglyceride, and phospholipid (PL) levels were significantly lower than those in the rats fed safflower oil. In PL fractions of serum, liver, lung, splenocytes, and peritoneal exudate cells (PEC), increases in linoleic and dihomo-gamma-linolenic acid contents and a decrease in arachidonic acid (AA) content were observed in the rats fed EPA or DHA. In addition, the EPA content increased in the rats fed EPA and DHA. In the rats fed EPA or DHA, a decrease of LTB4 productivity and an increase of LTBs productivity were observed in the PEC, in response to the treatment with 5 microM calcium ionophore A23187 for 20 min. The changes in leukotriene production were more marked in EPA-fed rats than in DHA-fed rats. These results suggest that dietary EPA affects lipid metabolism and leukotriene synthesis more strongly than DHA.     

Mevinolin, a competitive inhibitor of hydroxymethylglutaryl coenzyme A reductase, suppresses enterocyte esterification of exogenous but not endogenous cholesterol.

Mevinolin (lovastatin), a competitive inhibitor of hydroxymethylglutaryl-coenzyme A reductase, directly inhibited acyl-CoA cholesteryl acyltransferase in rabbit intestinal microsomes at a dose of 20 micrograms/ml or more. Lineweaver-Burk analysis showed a competitive type of inhibition with respect to oleoyl-CoA. In cultured intestinal Caco-2 cells, mevinolin reduced [14C]oleate incorporation into cholesteryl-esters by 86% of controls at doses as low as 0.1 micrograms/ml. However, in cells whose activity of acyl-CoA cholesteryl acyltransferase was stimulated 7-fold by 10 mM mevalonolactone, a significant inhibitory effect on cholesteryl-ester formation could not be detected, even at 40 micrograms/ml of mevinolin. In contrast, cells supplied with liposomal cholesterol or cholesterol derived from low-density lipoproteins showed a marked reduction of cholesteryl-ester formation in the presence of 10 or 0.1 micrograms/ml of mevinolin, respectively. It is concluded that the observed suppressive effects of mevinolin on cholesterol esterification in cultured Caco-2 cells are indirect and possibly caused by changes in the acyl-CoA cholesteryl acyltransferase substrate pool or intracellular cholesterol transport.     

Stimulation of vascular cell proliferation by beta-galactoside specific lectins

An investigation was conducted to assess the effects of various beta-galactoside specific lectins on the growth of vascular cells in vitro. The plant lectins from peanut (Arachis hypogaea), mushroom (Agaricus bisporus), and coral tree (Erythrina corallodendron) were used in these studies with the ultimate purpose of comparing those findings with data derived with the lectin isolated from rat lung. Peanut lectin was added to confluent and subconfluent cultures of smooth muscle cells (SMC), pulmonary arterial (PEC), and aortic endothelial cells (BAEC) at concentrations of 2, 3.5, and 7.0 micrograms/ml. There was a dose-dependent increase in cell proliferation for both confluent and subconfluent SMC, with maximal stimulation noted between 3.5 and 7 micrograms/ml of peanut lectin. A dose-dependent stimulation of PEC proliferation was also found with maximal stimulation between 3.5 and 7.0 micrograms/ml. Peanut lectin did not stimulate BAEC to multiply. The stimulation of PEC and SMC by peanut lectin could be prevented by the addition of 50 mM lactose. Peanut and mushroom lectin stimulated the proliferation of sparse cultures of SMC in a dose-dependent fashion in both standard (10% fetal bovine serum, or FBS) or low (0.5% FBS) serum to about the same degree. Coral tree lectin did not have a significant stimulation of proliferation under either serum conditions. The incorporation of [3H]thymidine into the DNA of PEC was increased 30 and 150% by peanut lectin and lung galaptin, respectively, under standard serum conditions. However, under low serum conditions, both lectins increased incorporation by about the same extent (93 and 78% for peanut lectin and galaptin, respectively). Both lectins produced a 30% increase in DNA synthesis by SMC under standard serum conditions, and about a 200% increase under low serum conditions. These studies indicate that beta-galactoside specific lectins such as lung galaptin have mitogenic activity toward vascular cells.     

Prostaglandin E2 promotes IL-4-induced IgE and IgG1 synthesis

PG of the E series are generally known to suppress immune responses, however, we have found that PGE synergizes with IL-4 to induce IgE and IgG1 production in LPS-stimulated murine B lymphocytes. PGE2 and PGE1 (10(-6) to 10(-8) M) significantly increase IgE and IgG1 production (up to 26-fold) at all concentrations of IL-4 tested. In addition to its effects on IgE and IgG1, PGE also causes a significant decrease in IgM and IgG3 synthesis, suggesting that PGE may promote IL-4-induced class switching. The specificity of the E series PG effect is demonstrated by the fact that PGF2 alpha (10(-6) M) does not alter production of any of these isotypes. Because PGE can mediate its effects through cAMP in some cases, we investigated the importance of cAMP levels in regulation of isotype expression. Other agents that increase intracellular cAMP levels (cholera toxin and dibutyryl cAMP) were assessed for their ability to regulate isotype differentiation. Cholera toxin (100 pg/ml) and dibutyryl cAMP (100 microM) significantly enhanced IgE and IgG1 production and diminished IgM and IgG3 synthesis. We also show that PGE and cholera toxin elevate intracellular cAMP in B lymphocytes in a dose-dependent manner. In contrast, PGF2 alpha (10(-6) M) and the B subunit of cholera toxin (100 pg/ml) did not increase cAMP and did not regulate the isotype of Ig produced, reiterating the importance of cAMP in enhancing isotype differentiation. Although PGE is known to inhibit a number of immune responses, our data show that it is not always inhibitory. PGE may play a role in atopy in vivo where PGE-secreting cells such as macrophages, follicular dendritic cells, and fibroblasts can promote IgE synthesis. This research emphasizes the importance of PGE in regulation of the humoral immune response and adds a new stimulatory action to the repertoire of known PGE effects.     

In vitro effect of biogenic amines on the hormone content of immune cells of the peritoneal fluid and thymus. Is there a hormonal network inside the immune system?

Immune cells contain different hormones and hormone-like molecules, such as insulin, endorphin, triiodothyronine (T3) histamine, serotonin. In earlier in vitro experiments insulin down-regulated histamine, serotonin and T3 content of thymus cells. Now we studied the effect of biogenic amines on the endorphin, T3, serotonin and histamine content of rat peritoneal and thymic cells. Cells were obtained from male rats of 100g body weight. 100 ng/ml serotonin or 300 ng/ml histamine was added for 30 min. After that the cells were prepared for flow cytometric analysis with antibodies to endorphin, T3, histamine and serotonin as primary antibodies and anti-rabbit IgG as secondary antibody. Finishing the measurements the cells were also studied by confocal microscopy. T3 concentration (binding of anti-T3 antibody) increased in peritoneal mast cells after serotonin treatment and in the monocyte-macrophage-granulocyte group after histamine treatment. Thymocytes' T3 content radically decreased after both treatments. Serotonin and histamine treatment also radically reduced the amine content of each other. Endorphin level was resistant to hormonal treatments. The results call attention to a possible hormonal network inside the immune system in which hormones produced by the immune cells themselves can influence each other.