Influence of gender and age on T-cell responses in a murine model of trauma-hemorrhage: differences between circulating and tissue-fixed cells.

Clinical studies indicate that peripheral blood lymphocyte functions are depressed following trauma; however, it is unclear whether tissue-fixed lymphocyte functions are also altered under those conditions. Moreover, the impact of gender and age on peripheral T-cell responses following trauma-hemorrhage (TH) are unknown. To study this, immature (approximately 3 wk of age), mature (approximately 7 wk of age), and aged (approximately 23 mo of age) male and proestrus female C3H/HeN mice were sham operated or subjected to trauma (i.e., midline laparotomy) and hemorrhagic shock (30+/-5 mmHg for 90 min). Twenty-four hours after resuscitation, blood and splenocytes were harvested and T-cell functions assessed. In immature animals, TH induced an enhanced immune response in the splenic compartment and a suppressed response in the peripheral blood mononuclear cells (PBMC) that was independent of gender. Differential responses were observed in cells from mature mice. Splenic responses were enhanced following TH, independent of gender, whereas PBMC displayed gender dimorphism with suppressed proliferation and T-cell helper 1 responses in males but not in females. A similar pattern was observed in cells from aged mice. Splenic T cells from male mice displayed a suppressed CD4-to-CD8 ratio after TH, whereas no such change was observed in cells from proestrus females. In contrast, only PBMC from mature males displayed a suppressed CD4-to-CD8 ratio after TH. Thus gender differences exist in PBMC responses after TH that do not necessarily correlate with changes in the tissue-fixed compartment. Age is also an important factor in the immune responses after TH. In view of this, both gender and age should be taken into consideration in evaluating the immune status and in treatment of TH shock.     

Effects of marrow donor and recipient age on immune responses

This report describes treatments to restore diminished splenic immune responses of old mice. Lethal irradiation, followed by young bone marrow and infant thymus transplants, restored the T cell mitogen response and the antibody-forming cell response against sheep red blood cells in the old mice. Although old bone marrow cells restore these immune responses in young recipients, as well as do young bone marrow cells, old bone marrow in old recipients did not improve their levels of response. Longevities of old recipients with rejuvenated responses were not increased, and aging of tail tendon collagen was not affected. The effect of lethal irradiation before the marrow transplant was shown to be minimal, by the use of unirradiated old W-anemic recipients. Parabiosing young mice with old partners caused impairment of these two immune responses in the young partners without enhancing them in the old partners. The old partners did not have increased longevities. To explain these results, we suggest the following hypothesis: old bone marrow contains precursors that produce suppressive factors or cells when in an old environment but not when in a young environment. However, these factors, if allowed to develop in an old environment, can function in a young parabiosed partner.     

In vitro immune response by murine bone marrow cells stimulated against soluble immune complexes.

Synchronized nonadherent bone marrow lymphocytes were stimulated with soluble immune complexes, in antigen excess formed by C3H/HeJ antibodies and various noncross-reacting protein antigens, in a suspension culture which allowed longterm cultivation. On binding of these complexes, lymphocytes underwent blast transformation with mitosis and formation of plasma cells which secreted specific antibodies to the antigen; a cyclic sequence of lymphocytes, blasts, and plasma cells was observed until the majority of the cell population appeared to be plasma cells. The relative percentage of mature plasma cells then decreased leaving mostly small lymphoid cells among which evidence suggests the presence of memory cells. Complexes at equivalence stimulated for the first few days, whereas antibody excess caused stimulation only initially followed by inhibition of the response. Antibodies passively added to the cultures inhibited the proliferative reaction; free antigen induced a typical secondary-type response.     

17 beta-Estradiol normalizes immune responses in ovariectomized females after trauma-hemorrhage

Recent studies indicate that immuneresponses in proestrus females are maintained after trauma-hemorrhagebut markedly depressed in ovariectomized females under such conditions.The current study tested the hypothesis that the decreased estrogenlevels after ovariectomy are responsible for this immune depression. Tostudy this hypothesis, ovariectomized female CBA/J mice were subjected to laparotomy (i.e., soft tissue trauma) and hemorrhagic shock (35 ± 5 mmHg for 90 min, then resuscitated) or sham operation. The micereceived either 17-estradiol (E2; 100 µg/25 g body wt) or vehiclesubcutaneously during resuscitation. Immune cells were isolated 24 h thereafter. Splenocyte proliferation and interferon-, interleukin(IL)-2, and IL-3 release were significantly depressed aftertrauma-hemorrhage in vehicle-treated mice, whereas these functions weremaintained in E2-treated mice. Peritoneal macrophage IL-1 and IL-6release and splenic macrophage IL-6 and IL-12 release were alsosignificantly depressed in vehicle-treated mice after trauma-hemorrhage, and release of these cytokines was restored by E2treatment. In summary our findings indicate that the depressed splenicand peritoneal immune responses after trauma-hemorrhage can benormalized by a single dose of E2. Thus estrogen appears to be thecausative factor in the maintenance of immunocompetence in femalesafter trauma-hemorrhage, and its administration to ovariectomized orpostmenopausal females should be helpful in preventing immunedepression under such conditions.

     

Interactive effects of social environment,age and sex on immune responses in Drosophila melanogaster

Social environments have been shown to have multiple effects on individual immune responses. For example, increased social contact might signal greater infection risk and prompt a prophylactic upregulation of immunity. This differential investment of resources may in part explain why social environments affect ageing and lifespan. Our previous work using Drosophila melanogaster showed that single‐sex social contact reduced lifespan for both sexes. Here, we assess how social interactions (isolation or contact) affect susceptibility to infection, phagocytotic activity and expression of a subset of immune‐ and stress‐related genes in young and old flies of both sexes. Social contact had a neutral, or even improved, effect on post‐infection lifespan in older flies and reduced the expression of stress response genes in females; however, it reduced phagocytotic activity. Overall, the effects of social environment were complex and largely subtle and do not indicate a consistent effect. Together, these findings indicate that social contact in D. melanogaster does not have a predictable impact on immune responses and does not simply trade‐off immune investment with lifespan.     

Mouse genetic background influences severity of immune responses following trauma-hemorrhage

Studies have shown that following bacterial infection or endotoxin administration, immune functions are regulated differently in mice of different genetic background. Since the susceptibility to sepsis following trauma-hemorrhage is dependant on the severity of injury, it is important to determine whether genetic background of the animal influence immune functions after trauma-hemorrhage. The aim of our studies, therefore, was to assess differences in the immune functions in genetically different strains of age-matched C3H/HeN and C57BL/6 male mice following trauma-hemorrhage. The analysis for immune functions included: proliferation of splenocyte and bone-marrow cells, IL-2 and IFN-gamma release by splenocytes, and TNF-alpha and IL-10 release by splenic, peritoneal, liver (Kupffer cell), and bone-marrow macrophages. The results show significant differences in splenocyte and bone-marrow functions, and in the release of the mediators of immune function by immune competent cells: (a) between the two genetic strains, and (b) in each mouse strain following trauma-hemorrhage. Thus, genetic background appears to significantly influence the severity of immune responses in males following trauma-hemorrhage.     

Antiviral immune responses of fully allogeneic irradiation bone marrow mouse chimeras

In (B10.BR----B10) chimeras infected with lymphocytic choriomeningitis (LCM) virus higher titers were attained in spleens and livers than in organs of the mice used for their construction, and the subsequent elimination was retarded, but eventually the virus was cleared. The numbers of LCM virus-specific CTL and their precursors as quantitated with chromium-release assay and limiting dilution method, respectively, were lower in chimeras than in B10.BR or C57BL/10J mice, and fewer were restricted for the haplotypes of the donors than of the recipients. The same was true with regard to antiviral effector cells, which were determined by adoptive immunization. The numbers of spleen cells releasing IgM and IgG antiviral antibodies were virtually as high in chimeras as they were in C57BL/10J and B10.BR mice. Transfer of immune splenocytes from either B10.BR or C57BL/10J mice resulted in incomplete virus elimination from the spleens of infected chimeras, whereas injection of a mixture of the two types of immune cells led to efficient clearance. We conclude that in the chimeras cells of both donor and recipient haplotypes participate in the infection, which is terminated by H-2k- and H-2b-restricted T lymphocytes that these animals are capable of generating. We conclude, furthermore, that clearance of the LCM virus from the tissues requires contact between effector and target cells.     

A murine model for human immune thrombocytopenic purpura and comparative analysis of multiple gene expression in bone marrow and spleen

Homeostasis of platelet number in human and other mammals is well maintained for prevention of minor bleeding and for other immunological functions,but the exact molecular mechanism responsible for immune thrombocytopenic purpura(ITP) has not been fully understood.In an effort to identify genetic factors involved in initiation of platelet production in response to bleeding injury or platelet destruction,we have successfully generated an animal model of human ITP via intraperitoneal injection of anti-platele...     

Influence of age on stem cells depends on the sex of the bone marrow donor

Ageing is often accompanied by an increase in bone marrow fat together with reduced bone volume and diseases of the bone such as osteoporosis. As mesenchymal stem cells (MSCs) are capable of forming bone, cartilage and fat tissue, studying these cells is of great importance to understand the underlying mechanisms behind age‐related bone diseases. However, inter‐donor variation has been found when handling MSCs. Therefore, the aim of this study was to investigate the effects of donor age and sex by comparing in vitro characteristics of human bone marrow‐derived MSCs (hBMSCs) from a large donor cohort (n = 175). For this, hBMSCs were analysed for CFU‐F capacity, proliferation, differentiation capacity and surface antigen expression under standardized culture conditions. The results demonstrated a significantly reduced CFU‐F number for hBMSCs of female compared to male donors. Furthermore, there was a significant decrease in the proliferation rate, adipogenic differentiation potential and cell surface expression of SSEA‐4, CD146 and CD274 of hBMSCs with an increase in donor age. Interestingly, all these findings were exclusive to hBMSCs from female donors. Further research should focus on postmenopausal‐related effects on hBMSCs, as the results imply a functional loss and immunophenotypic change of hBMSCs particularly in aged women.     

Effect of host age upon interleukin-2-mediated anti-tumor responses in a murine fibrosarcoma model

Summary The age-associated decline in immune function may be an important factor in both the pathogenesis of neoplastic diseases and the response to immunopharmacological therapies. With the increased efforts to develop immunotherapy with such agents as interferon and interleukin-2 (IL-2), the question of the effect of host age upon response is of practical importance. Phase I and phase II clinical trials of IL-2 have included primarily young patients, and toxicity and efficacy have not been reported with specific reference to host age. In this study, we examined young and old mice with regard to in vitro natural killer and lymphokine-activated killer (LAK) cell functions. We also assessed the effects of exogenously administered recombinant human IL-2 in tumor-bearing mice of various ages. We found that natural killer cell function was demonstrably lower in old mice but that LAK cell function was comparable (young versus old). Furthermore, IL-2 treatment was successful in increasing survival time in old mice, similar to results in young mice. Our observations allow the prediction that immune senescenceper se does not preclude successful anti-neoplastic treatment with IL-2.Supported by VA Merit Award (WBE) and a grant from the University of Wisconsin Graduate School     

The effects of age, sex and diet on the clastogenic action of cyclophosphamide in mouse bone marrow

7-week-old and 12-week-old mice of both sexes received either a control or protein-deficient diet for 3 weeks. Afterwards, they were given a single dose of cyclophosphamide (0.5 mg/10 g b.wt.) before being sacrificed. The relationship between age and the clastogenic action of cyclophosphamide can be observed in the bone marrow cells of male mice but not in those of female mice. 12-week-old males on a 75% protein-deficient diet have a lower frequency of cells with cyclophosphamide-induced chromosome aberrations than has the control group. On the contrary, 7-week-old males and females, and 12-week-old females, show that protein-deficient diets act synergistically with the clastogenic action of cyclophosphamide. These results are discussed taking the metabolism of the drug into account. Animal age also plays a role in the formation of chromosome rearrangements; this type of aberration is significantly more frequent in younger animals of both sexes than in older ones exposed to the drug.     

Androstenediol ameliorates alterations in immune cells cytokine production capacity in a two-hit model of trauma-hemorrhage and sepsis

Although administration of androstenediol (a metabolite of dehydroepiandrosterone) following trauma-hemorrhage (T-H) produces beneficial effects on inflammatory cytokines and organ function, it remains unknown whether this metabolite has any salutary effects in preventing alterations in immune cell cytokine production following a combined insult of T-H and sepsis. To examine this, male rats underwent laparotomy, hemorrhagic shock (mean BP 40 mmHg for 90 min) and resuscitation or sham operation. Androstenediol (1 mg/kg BW i.v.) or vehicle was administered at the end of resuscitation. Twenty hrs after T-H or sham operation, sepsis was induced by cecal ligation and puncture (CLP). Five hours thereafter, plasma cytokine levels and cytokine production of various immune cells were determined. In a separate set of experiments, survival was monitored for 10 days after the induction of sepsis. Administration of androstenediol markedly decreased plasma IL-6 and TNF-alpha levels following T-H and CLP. Furthermore, it prevented the increased production of IL-6 and TNF-alpha by Kupffer cells and alveolar macrophages and attenuated the decrease in IL-6 and TNF-alpha production by splenic macrophages; however, it had no significant effects on the depressed IL-6 and TNF-alpha production by PBMC following T-H and CLP. The depressed IL-2 and IFN-gamma production by splenocytes under those conditions was attenuated by the administration of androstenediol. Furthermore, survival rate following T-H and subsequent sepsis was improved by androstenediol treatment. Since androstenediol administration following T-H attenuated cytokine production and reduced mortality in a double-hit model of T-H and sepsis, this agent appears to be a novel and useful adjunct for maintaining the immune cell functions following T-H and for decreasing the mortality rate from subsequent susceptibility to sepsis.     

Augmentation of murine immune responses by amphotericin B.

Immunostimulant effects have been demonstrated in mice following single injections of amphotericin B or amphotericin methyl ester. Augmentation of both humoral and cell-mediated immune responses helps to explain the beneficial therapeutic effects observed in human and murine neoplasms after administration of amphotericin. Relevant to its immunological adjuvant properties, amphotericin produces striking reversible changes in murine thymus and splenic weights and in lymphoid organ histology. The chemical purity, nonimmunogenicity, and permissible toxicity of amphotericin recommend it as a model for the study of the cellular and molecular mechanisms of immunological adjuvants.     

Effect over time of in-vivo administration of the polysaccharide arabinogalactan on immune and hemopoietic cell lineages in murine spleen and bone marrow.

Current evidence indicates an immunostimulating role for complex carbohydrates, i.e., polysaccharides, from several plant sources. In the present work, we determined the specific in vivo effects, with time of administration, of one such compound, a neutral arabinogalactan from larch not only on immune (lymphoid) cells, but also on natural killer (NK) lymphoid cells, as well as a variety of other hemopoietic cells in both the bone marrow and spleen of healthy, young adult mice. The latter were injected daily (i.p.) with arabinogalactan (500 microg in 0.1 ml pH 7.2 phosphate buffered saline-PBS) for 7 or 14 days. Additional, aged (1 1/2-2 yr) mice were similarly injected for 14 days only. Control mice were given the PBS vehicle in all cases, following the above injection regimen. Animals from all groups were sampled 24 h after the final injection and the immune and hemopoietic cell populations in the bone marow and spleen were assessed quantitatively. The results indicated that immediately following either 7 or 14 days of arabinogalactan administration to young, adult mice, lymphoid cells in the bone marrow were significantly decreased (p < 0.004; p < 0.001, respectively) relative to controls but remained unchanged at both time intervals in the spleen. NK cells, after 7 days of arabinogalactan exposure, were also decreased significantly in the bone marrow (p < 0.02), but unchanged in the spleen. After 14 days' exposure to the polysaccharide, NK cells in the bone marrow had returned to normal (control) levels, but were increased in the spleen (p < 0.004) to levels greater than 2-fold that of control. Among other hemopoietic cell lineages, none was influenced in the bone marrow or spleen by one-week administration of arabinogalactan; however, after two-week exposure, precursor myeloid cells and their mature (functional) progeny (granulocytes), were significantly reduced in the spleen (p < 0.043; p < 0.006, respectively), as were splenic monocytes (p < 0.001). These lineages in the bone marrow, however, remained steadfastly unaltered even after 14 days of continuous exposure to the agent. Of the vast cascade of cytokines induced in the presence of this polysaccharide, it appears that immunopoiesis- and hemopoiesis-inhibiting ones are most prevalent during at least the first two weeks of daily exposure.     

Protective effects of finasteride on the pulmonary immune response in a combined model of trauma-hemorrhage and polymicrobial sepsis in mice

Literature supports findings about a gender specific outcome following multiple trauma. Male sex hormones such as dihydrotestosterone (DHT) exert deleterious effects on the posttraumatic immune response whereas increased estradiol concentrations are correlated with improved outcome. Pretreatment with the 5α-reductase inhibitor finasteride resulted in an improved outcome following trauma-hemorrhage (TH) in mice. The present study tested the hypothesis that finasteride exerts beneficial effects on the posttraumatic immune response also in a combined setting of TH and sepsis when administered during the resuscitation process.

Material and Methods

Male C57BL/6N-mice were subjected to TH (blood pressure, 35 mm Hg, 60 min) followed by finasteride application and fluid resuscitation. Thereafter, finasteride was administered every 12 h. 24 h after TH, sepsis was induced by cecal ligation and puncture (CLP) or sham operation was performed. Plasma cytokines (MIP-1α, MIP-1β, TNF-α, MCP-1, IL-6), productive capacity by alveolar macrophages (AM) and systemic estradiol levels were determined 4 h thereafter. The expression of pro-inflammatory mediators in lung tissue was evaluated by PCR. Pulmonary infiltration of PMN was determined by immunohistochemical staining.

Results

Finasteride treatment resulted in a reduced posttraumatic cytokine secretion of AM as well as in a decreased concentration of MCP-1 and MIP-1β in lung tissue. Systemic estradiol levels were increased following finasteride treatment.

Conclusion

Finasteride mediates salutary effects on the pulmonary immune response using a therapeutical approach following TH–CLP in mice. Thus, finasteride might represent a relevant therapeutic substance following major trauma also in the clinical setting.     

How sex and age affect immune responses,susceptibility to infections,and response to vaccination

Do men die young and sick, or do women live long and healthy? By trying to explain the sexual dimorphism in life expectancy, both biological and environmental aspects are presently being addressed. Besides age-related changes, both the immune and the endocrine system exhibit significant sex-specific differences. This review deals with the aging immune system and its interplay with sex steroid hormones. Together, they impact on the etiopathology of many infectious diseases, which are still the major causes of morbidity and mortality in people at old age. Among men, susceptibilities toward many infectious diseases and the corresponding mortality rates are higher. Responses to various types of vaccination are often higher among women thereby also mounting stronger humoral responses. Women appear immune-privileged. The major sex steroid hormones exhibit opposing effects on cells of both the adaptive and the innate immune system: estradiol being mainly enhancing, testosterone by and large suppressive. However, levels of sex hormones change with age. At menopause transition, dropping estradiol potentially enhances immunosenescence effects posing postmenopausal women at additional, yet specific risks. Conclusively during aging, interventions, which distinctively consider the changing level of individual hormones, shall provide potent options in maintaining optimal immune functions.