Response Of Splenic Lymphocytes Research Articles

Differential Effects of Physical and Psychological Stressors on Immune Functions of Rats

To study the effects of different types or durations of stressors on immune functions, male Fischer rats were exposed to chronic physical (electric foot shock) or psychological (non-foot shock) stress induced in the communication box. Superoxide production by alveolar macrophages (AMs), mitogen-induced splenic lymphocyte proliferation, and splenic natural killer (NK) cell cytolysis were examined in vitro. Repeated exposure to physical stress suppressed superoxide production by AMs ( m 58%, p <0.05 for opsonized zymosan (OZ) and m 51%, p <0.05 for phorbol 12-myristate 13-acetate (PMA)), although psychological stress suppressed superoxide production after 24 h of repeated exposures ( m 40%, p <0.05 for OZ and m 47%, p <0.05 for PMA). Acute suppression of the blastic response of splenic lymphocytes was only found in the physical stress group ( p <0.05), although the chronic effects were only found in the psychological stress group ( p <0.05). NK cell activity was suppressed immediately after the acute physical stress ( m 30%, p <0.05 ), but no effects were found in the psychological stress group. These results underline the importance of distinguishing between physical versus psychological stressors when examining the effects of stress on immune functions.

Immunomodulatory activity of septilin, a polyherbal preparation.

Septilin is a polyherbal preparation, claimed to be effective in conditions such as chronic stubborn URTI, tonsillitis, cutaneous infections, dental infections and also prescribed as a health supplement. In view of this, the present experimental study was undertaken to evaluate the effect of Septilin on different arms of the immune system. The experimental animals (male albino rats and mice) were divided into three groups. Group I received distilled water; group II received Septilin in a dose of 1 g/kg (rats) or 1.5 g/kg (mice); group III received Septilin 2 g/kg (rats) or 3 g/kg (mice) orally for 28 days. They were evaluated for immunological function on day 29 by studying weight gain, resistance against E. coli sepsis, haemogram, phagocytic activity of PMN cells and reticuloendothelial system, delayed hypersensitivity to oxazolone and the plaque forming cell response of splenic lymphocytes to sheep erythrocytes. Neither of the doses of Septilin altered weight gain, absolute lymphocyte counts, or host resistance against E. coli sepsis. The higher dose of Septilin reduced phagocytic activity of the PMN cells/reticuloendothelial system, but both doses increased the percentage and absolute number of circulating neutrophils, stimulated humoral immunity and suppressed cellular immunity. Thus, Septilin has dual effects on the immune system, with lower doses showing greater stimulant and higher doses showing predominantly suppressant effects.

Inhibition of intracellular peroxides and apoptosis of lymphocytes in lupus-prone B/W mice by dietary n-6 and n-3 lipids with calorie restriction.

Our earlier studies have shown that calorie restriction and n-3 fatty acids inhibit autoimmune disease and prolong life span. Experiments were designed to study the alteration of apoptosis and its mediators in B/W mice fed either n-6 fatty acids [5% corn oil (CO)] or n-3 fatty acids [5% fish oil (FO)] and either allowed access to the diet ad libitum (AL) or restricted in caloric intake by 40% (CR), from 4 weeks of age. At 4 months (young) and 9 months (old) mice were killed, splenic lymphocytes were isolated, and apoptosis was measured with Annexin V and PI staining. Apoptosis was decreased in splenic lymphocytes from both young and old CR mice compared to their respective AL-fed control groups regardless of fat source. Increasing apoptosis with age was observed in CO/AL, CO/CR, and FO/AL mice which correlated closely with significantly higher cellular peroxides measured by flow cytometry using dichlorofluourescein diacetate (DCFH-DA), whereas in both CO/CR and FO/CR peroxide levels remained low in old mice. Furthermore, CR increased the proliferative response of splenic lymphocytes and decreased the Fas (CD95) and Fas-L protein expression in CD4+ lymphocytes from old mice. Higher levels of Fas and Fas-L expression were observed in old mice compared to young mice. Bcl-2 levels were elevated in both young and old CR groups compared to the respective AL groups. Calorie restriction prevented the loss of CD8 cells in old mice fed both the CO and the FO diet. In summary, CR resulted in decreased apoptosis accompanied by alterations in Fas, Fas-L, and Bcl-2 expression in old mice, increased life span, and delayed onset of kidney disease.

Oral Exposure to Alloantigen Generates Intragraft CD8+ Regulatory Cells

We have previously reported that oral administration of allogeneic rat spleen cells before kidney allotransplantation significantly prolongs graft survival. This prolongation was alloantigen specific and was associated with a decrease in graft-infiltrating cells (GIC) and an increase in transcription of IL-4 mRNA in the GIC. In this study increased splenic mixed lymphocyte responses from animals orally exposed to alloantigen before kidney transplantation suggested that the kidney allograft prolongation was not due to a masking of allorecognition, but to an immunomodulation of the immune response. We have assessed GIC T cell subsets on day 5 post-transplant and found decreased numbers of CD4(+) T cells in fed animals compared with controls, but there was no change in CD8(+) T cell numbers. The CD8(+) GIC from fed animals transcribed substantial levels of perforin, granzyme, and Fas ligand mRNA, indicating the presence of active CTL. Direct CTL assays showed that the GIC from fed recipients exhibited higher allo-CTL activity than GIC from control unfed recipients. In addition, the CD8(+) GIC exhibited high levels of IL-4 mRNA, suggesting Tc2-type regulatory cells. Prolonged graft survival in the face of active CTL and Tc2 cells suggests the presence of a CD8(+) regulatory cell population in the allograft. To confirm this, cell transfer experiments were performed. Prolongation of graft survival was transferred from rats orally exposed to alloantigen to naive animals by transfer of CD8(+) GIC. This is the first report that oral exposure to alloantigen prolongs kidney allograft survival by the generation of intragraft CD8(+) regulatory cells.

Proinsulin C peptide obviates sympathetically mediated suppression of splenic lymphocyte activity in rats.

To investigate whether proinsulin C peptide influences sympathetic nerve activity directly or indirectly through parasympathetic nerve activity. The proliferative response of splenic lymphocytes to Concanavalin A (ConA response) which is known to be suppressed by subjection of rats to footshock or intracerebroventricular injection of corticotropin-releasing factor through sympathetic nerve activation was measured. Effect of C peptide alone or before subjection to footshock or injection of corticotropin-releasing factor was examined. Intraperitoneal injection of C peptide was without effect on the basal ConA response, while subjection to footshock or injection of corticotropin-releasing factor lowered it. In contrast, prior injection of C peptide obviated the footshock and corticotropin-releasing factor-induced suppression of the response. When given intracerebroventricularly, C peptide was also effective at much smaller doses. Prior injection of atropine cancelled the C-peptide effects. Our results indicate that C peptide counteracts the sympathetic nerve-mediated suppression of splenic lymphocyte proliferation in an atropine-sensitive manner. Thus, C peptide probably activates the parasympathetic nervous system through the afferent mechanism, that in turn antagonizes the sympathetic nerve-mediated suppression of splenic lymphocyte functions.

Influence of repeated infestations with pathogen-free Ixodes scapularis (Acari: Ixodidae) on in vitro lymphocyte proliferation responses of C3H/HeN mice.

In the United States, Ixodes scapularis Say has been implicated as the vector of at least three human pathogens. Tick induced modulation of host immunity is increasingly recognized as an important factor in successful transmission or establishment of tick-borne pathogens. This study was conducted to determine the effects of repeated infestations with pathogen-free I. scapularis nymphs on in vitro proliferative responses of splenic lymphocytes from C3H/HeN mice. Lymphocytes from repeatedly infested and uninfested mice were exposed to concanavalin A (Con A), Escherichia coli Castellini & Chalmers lipopolysaccharide (LPS), or I. scapularis salivary gland soluble proteins (SGSP), to determine if lymphocyte responses differed between tick-exposed and nonexposed mice. Female C3H/HeN mice were infested one to four times with pathogen-free I. scapularis nymphs, with a 14-d tick-free period between each exposure. After each infestation, tick biology parameters were measured and lymphocyte proliferative responses assessed. Acquired resistance to I. scapularis was not evident in mice subjected to tick feeding. Significant differences in the responses of lymphocytes exposed to I. scapularis SGSP were observed between infested and noninfested mice. In contrast, few differences between infested and noninfested mice were evident for lymphocytes exposed to Con A or LPS. Our results suggest that repeated exposure to I. scapularis nymphs does not affect Con A or LPS-induced proliferation of splenic lymphocytes, but significantly effects lymphocyte responses to tick salivary gland antigens.

Change of cytokine balance in diet-induced obese mice

Although decreased T-cell function has been observed in obese human subjects and genetically obese animals, the precise role of immune functions in obesity is still unclear. To investigate immune functions in obesity, we examined the proliferative responses of splenic lymphocytes and their capacity to produce cytokines in the presence or absence of leptin, the protein produced by the obese gene, in diet-induced obese and control mice. For induction of obesity, C57BL/6J mice were fed a high-fat diet for 13 weeks. In mice fed the high-fat diet, body weight, fat pad weight, and tumor necrosis factor (TNF) α production by adipocytes were significantly increased relative to mice fed the normal diet. Lipopolysaccharide (LPS) stimulated proliferation of cultured splenocytes from diet-induced obese mice was also increased. However, production of interleukin (IL)-2 by splenic lymphocytes from obese mice was suppressed, whereas interferon (IFN)-γ and IL-4 production was increased. Exogenous lepitn regulated the cytokine production by cultured splenocytes from control and obese mice, respectively (upregulation of IFN-γ and downregulation of IL-2 in control mice, and downregulation of IL-4 in obese mice). These results suggest that changes in cytokine production by splenic lymphocytes in obesity are indicative of altered immune functions that might contribute to related complications, although the effect of difference in nutrient intake (macro and micro) may also have contributed to the changes.

Gender-related differences in murine T- and B-lymphocyte proliferative ability in response to in vivo [Met 5]enkephalin administration

Gender-related differences in response to drugs of abuse, such as cocaine and morphine, have been reported both in humans and in experimental animals. Besides causing analgesia, morphine has recently been shown to exert strong immunosuppressive activity. However, no data on the influence of gender on the immunomodulatory effects of morphine or opioid peptides have been reported yet. The aim of this study was to test the influence of gender on the immunomodulatory ability of the endogenous opioid peptide [Met 5]enkephalin (MENK) in mice. This was done by comparing the proliferative ability of splenic T- and B-lymphocytes 14 h after systemic (intraperitoneal; i.p.) administration of [Met 5]enkephalin (2.5, 5 or 10 mg/kg body weight). The proliferative ability of T- and B-lymphocytes was assessed by testing their in vitro response to graded concentrations of the T- and B-cell mitogens, concanavalin-A (Con-A) and lipopolysaccharide (LPS), respectively. The results obtained showed that [Met 5]enkephalin, at a dose of 2.5 mg/kg, enhanced the proliferative ability of T-lymphocytes in male mice, but not in female mice. Similarly, [Met 5]enkephalin, at doses of 2.5 and 5 mg/kg, enhanced the proliferative ability of splenic B-lymphocytes in male mice, whereas in female mice a decrease was observed ([Met 5]enkephalin 2.5 mg/kg, LPS 10 μg/ml). [Met 5]enkephalin, at a dose of 10 mg/kg, did not affect the proliferative ability of either lymphocyte population, regardless of gender. The [Met 5]enkephalin-induced stimulatory effect on both T- and B-lymphocyte proliferation was reversed by naloxone (10 mg/kg body weight), injected prior to [Met 5]enkephalin, suggesting an involvement of opioid receptors. Thus, the data presented provide evidence for the gender-related response of murine splenic lymphocytes to immunomodulation by [Met 5]enkephalin, administered in vivo. This finding may be relevant to the potential use of [Met 5]enkephalin in adjuvant therapy for immunocompromised states, such as acquired immunodeficiency syndrome (AIDS) or malignancies.

Central leptin suppresses splenic lymphocyte functions through activation of the corticotropin-releasing hormone-sympathetic nervous system

Leptin is one of the key afferent signals that regulate food intake and energy expenditure by acting on specific receptors in the hypothalamus. Recently, leptin was reported to activate the peripheral immune system by acting directly on lymphocytes. To elucidate the brain-mediated participation of leptin in the modulation of peripheral immune functions, we examined the effects of intracerebroventricular (icv) injection of murine recombinant leptin on the proliferative response to Concanavalin A (ConA response) of splenic lymphocytes in rats. The ConA response of splenic lymphocytes was markedly reduced 30 min after icv injection of leptin. The suppressive effect of leptin was abolished completely either by surgical severing of the splenic nerves or by icv injection of an antibody against corticotropin-releasing hormone (CRH), but only partially by an anti-urocortin antibody. Icv injection of CRH and urocortin also suppressed the ConA response of splenic lymphocytes, and the effect of urocortin was prevented by the anti-CRH antibody, while that of CRH was not prevented by the anti-urocortin antibody. These results suggest that leptin suppresses peripheral lymphocyte functions, in contrast to the direct activating effects, indirectly through the activation of the CRH (urocortin)-sympathetic nervous system.

Maternal modulation of neonatal immune system development.

Changes in programming of neonatal immune development were effected through maternal immune modulation (Leishmania major inoculation). In progeny of these dams, immune profiles in both blood and spleen were changed throughout the neonatal period and were pronounced after weaning. White blood cell (WBC) and lymphocyte counts in blood of 45-day-old progeny were two-fold less than control animals. In blood, proportions of B cells were greater, while T helpers, Tc/s and NK cells were less than in controls. In contrast, proportions of splenic B and NK cells were greater than controls. But, proportions of all T and Tc/s cells on d20 and 45 were lower than controls. In blood, absolute numbers of all T, Th naïve and Th memory cells were lower than in controls. In contrast, in the spleen, numbers of NK, T and Th naïve and memory cells were up to 200% greater than in control pups. Cytokine responses of splenic lymphocytes stimulated through CD3 ligation revealed no difference in IL-4 production. In contrast, IL-2 and IFNγ were lower on d45 and 5, respectively, in the experimental compared to control mice. These data support the hypothesis that maternal immune events during gestation can modulate the pattern of immune development in offspring.

Decreased mitogen response of splenocytes in senescence accelerated mice (SAM-P1) is not restored by high vitamin E diet

We have previously found that vitamin E (VE) has an ability to restore the decreased mitogen response of splenocytes in spontaneously hypertensive rats (SHR) as a model of aging. The aim of this study is to investigate whether high VE diet can restore the decreased mitogen response of splenocytes in SAM-P1 as mouse model of aging. Male SAM-P1 and -R1 as control, 9 months old, were fed control (50 mg VE/kg diet) or high VE diet (585 mg VE/kg diet). Male SAM-R1, 4 weeks old, were used as young control. After 4 weeks, they were killed under anesthesia and their cellular immune functions were assayed. There was no significant differense in serum VE concentration between old SAM-R1 and -P1. In addition, high VE diet induced the similar increase of serum VE concentration in both old SAM-R1 and -P1. Mitogen response of splenic lymphocytes with concanavalin A (Con A) was remarkably decreased in SAM-P1 compared with those of young and old SAM-R1. High VE diet did not have the ability to restore the decreased mitogen response of splenic lymphocytes in SAM-P1. The percentage of adherent cells, mainly macrophages (Mø), in splenocytes was also remarkably decreased in old SAM-P1. Furthermore, Mø isolated from splenocytes of SAM-P1 did not have the enhancing effect on proliferation of splenic lymphocytes from young SAM-R1. These results suggest that the decreased mitogen response of splenic lymphocytes in SAM-P1 is not restored by high VE diet and may be associated to the decreases of both number and function of Mø.

Blockage of interleukin-6 receptor ameliorates joint disease in murine collagen-induced arthritis.

To clarify the role of interleukin-6 (IL-6) in the pathogenesis of collagen-induced arthritis (CIA). CIA was induced by immunizing twice at a 3-week interval with bovine type II collagen (CII) emulsified with complete adjuvant. Rat anti-mouse IL-6 receptor (anti-IL-6R) monoclonal antibody MR16-1 or isotype-matched control antibody KH-5 was then injected once intraperitoneally. Symptoms of arthritis were evaluated with a visual scoring system, and serum anti-CII antibody and IL-6 levels were measured by enzyme-linked immunosorbent assay. In addition, the CII responsiveness of splenic lymphocytes from mice with CIA was examined. In mice with CIA, excess production of IL-6 in sera was observed within 24 hours after the first CII immunization, and then rapidly decreased. Serum IL-6 increased again beginning 14 days after immunization, in conjunction with the onset of arthritis. When MR16-1 was injected immediately after immunization with CII, it inhibited the development of arthritis in a dose-dependent manner. Furthermore, MR16-1-treated mice exhibited lower serum levels of IgG anti-CII antibody and reduced responsiveness of lymphocytes to CII. This suppressive effect was observed when MR16-1 was injected on day 0 or 3, but not when injected on day 7 or 14. IL-6 produced after CII immunization appears to play an essential role in the immunity to CII, and anti-IL-6R antibody reduces the development of CIA by suppressing IL-6 signal transduction.

Effects of food restriction and exercise training on mitogen response of splenic lymphocytes in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of spontaneous non-insulin dependent diabetes mellitus (NIDDM)

We investigated whether mitogen response is impaired in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, and the effect of exercise training and food restriction on mitogen response of their splenocytes. OLETF rats were divided into the following groups at the age of 16 weeks; sedentary, exercise-trained and food-restricted (70% of the food intake in sedentary rats). Both exercise training and food restriction significantly suppressed plasma level of glucose, and serum levels of triglycerides and cholesterol. In addition, plasma level of insulin was significantly increased by both exercise training and food restriction. Mitogen response of splenocytes showed a marked decrease in OLETF rats compared to that of non-diabetic rats (Long-Evans Tokushima Otsuka; LETO), especially in PHA stimulation. Although both exercise training and food restriction did significantly improve the development of diabetes mellitus in OLETF rats, the decreased mitogen response of splenocytes was not improved. In particular, mitogen responses of splenocytes with PHA and Con A were further suppressed by food restriction. These results suggest that food restriction and exercise training do not have beneficial effects on decreased cellular immune function in NIDDM rats, whereas they improved the state of NIDDM.

Decreased mitogen response of splenic lymphocytes in obese Zucker rats is associated with the decreased expression of glucose transporter 1 (GLUT-1)

We reported previously that obesity is a risk factor for deteriorating cellular immune functions in aging. However, the mechanism by which obesity decreases cellular immunity remains to be elucidated. To determine the mechanism of the decrease in cellular immunity with obesity, lean (Fa/?) and obese (fa/fa) 12-mo-old Zucker rats were used. The mitogen response of splenic lymphocytes in obese Zucker rats was significantly lower than that of lean Zucker rats, which was not restored by in vitro treatment with indomethacin (10 micromol/L), an inhibitor of prostaglandin E2 (PGE2). In addition, PGE2 production by splenic lymphocytes was not greater in obese than in lean Zucker rats. Glucose consumption by splenic lymphocytes after in vitro incubation with concanavalin A (conA) for 48 h was also significantly lower in obese Zucker rats. Expression of glucose transporter 1 (GLUT-1), analyzed by Western blot analysis, was lower in splenic lymphocytes of obese than in lean Zucker rats. However, the expression of the conA receptor in splenic lymphocytes, analyzed by flow cytometry with fluorescein isothiocyanate-conjugated conA, was not significantly different between lean and obese Zucker rats. In conclusion, the decreased mitogen response of splenic lymphocytes in obese Zucker rats may be due in part to the decreased uptake of glucose as the main energy source for lymphocytes at the stage of proliferation and may be associated with the decreased expression of GLUT-1.

Prenatal Stress Depresses Immune Function in Rats

KAY, G., N. TARCIC, T. POLTYREV AND M. WEINSTOCK. Prenatal stress depresses immune function in rats. PHYSIOL BEHAV 63(3) 397–402, 1998.—The aim of the present study was to determine the effect of prenatal stress on immune function in rats. Pregnant rats were stressed by noise and light, three times weekly throughout pregnancy. Experiments were performed on male and female offspring aged 2 months. Cellular immune responses of splenic lymphocytes to B-cell (pokeweed mitogen (PWM) and T-cell (phytohemagglutinin (PHA)) mitogens were measured by [ 3H]thymidine uptake, and natural killer (NK) cell cytotoxicity in blood and splenic lymphocytes was measured against the murine T-cell lymphoma, YAC-1, by a 4-h [ 51Cr] release assay. Prenatal stress suppressed immune function as shown by a) decreased NK cytotoxicity in splenic and blood lymphocytes, indicating that the effect was not confined to a particular immune compartment, and b) decreased rate of proliferation of splenic lymphocytes to PWM and a smaller depressant effect on their response to PHA. The suppression of B-cell proliferation was more marked in the female and that of NK cell cytoxicity, in the male. Prenatal stress did not alter the distribution of subsets of lymphocytes, in either the spleen or blood, indicating that the reduction in proliferative and cytotoxic activity resulted from functional modifications of effector mechanisms in the cells rather from alterations in their migration between immune compartments. The mechanisms underlying this effect of prenatal stress are not clear but could result from an action of maternal stress hormones on the developing fetal neuroendocrine system.

The Effect of Cold Stress on Lymphocyte Proliferation in Fetal Ethanol‐Exposed Rats

Prenatal ethanol exposure and stress have each been shown to have significant effects on the immune system. This study examined the possible interactive effects of prenatal ethanol exposure and exposure to stress later in life on the immune system. Differential vulnerability to these challenges in female and male offspring was assessed. At 5 to 6 months of age, female and male offspring from prenatal ethanol-exposed (E), pair-red (PF), and ad libitum-fed control (C) conditions were exposed to 0, 1 or 3 days of cold (4 degrees C). At the end of the cold period, the proliferative response of splenic lymphocytes to the mitogens concanavalin A (Con A) and pokeweed mitogen (PWM) was assessed. The data demonstrate a significant interactive effect between prenatal ethanol exposure and cold stress in female offspring. After 1 day of cold stress, E females had significantly increased PWM-induced lymphocyte proliferation compared with PF and C females, and significantly increased Con A-induced lymphocyte proliferation compared with PF females. There were no differences in PWM or Con A-induced lymphocyte proliferation among E, PF, and C females after 0 or 3 days of cold stress, nor among E, PF, and C males on any test day. Regardless of prenatal treatment, females exposed to 1 or 3 days of cold had significantly greater basal plasma corticosterone levels than females not exposed to cold. In contrast, only E males exposed to 1 or 3 days of cold had significantly increased basal plasma corticosterone levels, compared with E males not exposed to cold; PF and C males showed no significant change in basal corticosterone after cold stress. These data demonstrate that, in response to the challenge of cold stress, changes in lymphocyte proliferation to PWM and Con A may occur selectively in E females. Moreover, the interactive effects of prenatal ethanol and cold stress may result in enhanced rather than suppressed immune responsiveness.

A unique response to staphylococcal enterotoxin B by intrahepatic lymphocytes and its relevance to the induction of tolerance in the liver.

It has been reported that the intrahepatic lymphocyte (IHL) population is somewhat differently constituted from lymphocytes in other lymphoid tissues. Staphylococcal enterotoxin B (SEB) is a superantigen which can induce T-cell tolerance in mice. The authors investigated the in vitro and in vivo responses of mouse IHL to SEB. An intravenous injection of SEB did not result in the augmentation of the proliferative response of IHL, while mesenteric and splenic lymphocytes (mLNC and SPC, respectively) had augmented responses. Interleukin-2 (IL-2) mRNA was clearly detected in mLNC and SPC by reverse transcriptase-polymerase chain reaction (RT-PCR) shortly after the administration of SEB, but it was scarcely expressed in IHL. The expression of CD25 (IL-2 receptor) was also augmented in mLNC and SPC in the early period, while it was not changed in IHL. These findings suggested that the time required for tolerance induction is different locally and that the loss of augmentation of IL-2 and IL-2 receptor production by IHL may be relevant to the rapid induction of T-cell tolerance in the liver.

ATTENUATION OF LETHAL GRAFT-VERSUS-HOST DISEASE BY INHIBITION OF NITRIC OXIDE SYNTHASE1

We have previously demonstrated that administration of the nitric oxide (NO) synthesis inhibitor aminoguanidine (AG) to mice undergoing nonlethal graft-versus-host disease (GVHD) results in less destruction of host tissue and enhanced proliferative responses of splenic lymphocytes. Subsequently, we have determined whether the amelioration of GVHD pathology associated with inhibition of NO synthesis affects survival in a lethal GVHD model. Utilizing a C57BL/6 to C57BL/6xDBA2JF1 model, administration of parental lymph node lymphocytes instead of splenocytes results in 80-90% lethality by week 4 after GVHD induction. Administration of AG resulted in significantly decreased lethality coincident with decreased serum NO2- + NO3- levels. AG therapy had no effect on donor anti-host cytolytic T cell activity, which indicates that destruction of host tissue via this pathway was unaffected by the therapy. Histological evaluation of spleen, small intestine, bone, and mesenteric lymph node did not reveal any difference in the histological correlates of disease in the treated mice. AG increased various hematopoietic indices, including red blood cell count, white blood cell count, and hemoglobin, which indicates that the disruption of hematopoiesis during acute GVHD is mediated in part by NO. In addition, the number of GVHD mice with endogenous bacterial infections in the spleen and liver was significantly decreased in mice receiving AG therapy. These data indicate that NO plays a detrimental role during GVHD that appears to result in decreased hematopoietic indices and concomitant susceptibility to bacterial infection.

Ventromedial hypothalamus suppresses splenic lymphocyte activity through sympathetic innervation

The ventromedial hypothalamic nucleus (VMH) has been proposed to be a locus intimately associated with sympathetic facilitation in peripheral tissues. To investigate a possible role of the VMH in controlling peripheral immune functions, we examined the effects of VMH stimulation on proliferative activity of lymphocytes isolated from the spleen in rats. Electrical stimulation of the VMH (2 s at every 30 s for 30 min) caused a remarkable decrease in the mitogenic response of splenic lymphocytes to Concanavalin A, whereas the stimulation of other hypothalamic regions such as the paraventricular nucleus did not show any significant effects. The suppressive effect of VMH stimulation was not influenced after adrenalectomy, suggesting a minor role of the adrenocortical system. In contrast, pretreatments with a ganglionic blocking agent (chlorisondamine) and a β-adrenergic receptor antagonist (propranolol) completely reversed the suppressive effect. Surgical severing of the sympathetic nerves entering the spleen also reversed the effect of VMH stimulation. Together with the previous finding that VMH stimulation activates the splenic sympathetic nerves, it is concluded that the VMH suppreses the proliferative activity of splenic lymphocytes through the activation of sympathetic nerves via the β-adrenergic pathway.

Prenatal exposure of balb/c mice to ochratoxin A: Effects on the immune system in the offspring

Effects of prenatal exposure to the mycotoxin ochratoxin A (OA) on the immune system were evaluated in Balb/c mice. Dams were exposed to OA in their diet at doses of 0.18 (control), 30 or 200 μg/kg before and during gestation. At birth, pups were cross-fostered to non-exposed dams. OA exposure of the dams did not influence reproductive outcome, that is, the numbers of litters, litter sizes and body weight of the pups. Flow cytomety analysis of T-lymphocyte subpopulations on days 14 and 28 postpartum revealed a decrease in the percentages of splenic CD4 + and CD8 + cells in offspring from the high-dose group (200μg/kg diet), but no significant alterations in absolute numbers of these cell populations nor in the total numbers of splenocytes were observed. In the thymus, a relative as well as an absolute increase in the CD4 + subpopulation was seen in exposed pups on day 14. On day 28, the absolute numbers of CD4 +, CD8 + and CD4 +CD8 + (double positive) cells were increased, reflecting an elevated number of thymocytes in the high-dose group. No significant differences were found in the proliferative responses of splenic or thymic lymphocytes to mitogens, or in the production of interleukin-2 in concanavalin A-stimulated cell cultures. Further, the plaque-forming cell response to sheep red blood cells and the humoral antibody response to the viral antigen PR8 were not affected by prenatal exposure to OA. No significant differences in natural killer cell activity were observed. The results indicate that exposure of dams to relatively low levels of dietary OA alters absolute and relative numbers of lymphocyte subpopulations in lymphoid organs, but does not suppress immune functions in the offspring.