Molecular mechanism of jet fuel induced immune suppression

Dermal exposure to jet fuel suppresses the immune response. Immune regulatory cytokines, and biological modifiers, including platelet activating factor, prostaglandin E2, and interleukin-10 have all been implicated in the pathway leading to immunosuppression. It is estimated that approximately 260 different hydrocarbons are found in JP-8 (jet propulsion-8) jet fuel, and the identity of the immunotoxic compound is not known. The recent availability of synthetic jet fuel (S-8), which is devoid of aromatic hydrocarbons, made it feasible to design experiments to test the hypothesis that the aromatic hydrocarbons are responsible for jet fuel induced immune suppression. Applying S-8 to the skin of mice does not up-regulate the expression of epidermal cyclooxygenase-2 nor does it induce immune suppression. Adding back a cocktail of 7 of the most prevalent aromatic hydrocarbons found in jet fuel to S-8 up-regulated cyclooxygenase-2 expression and induced immune suppression. Cyclooxygenase-2 induction can be initiated by reactive oxygen species (ROS). JP-8 treated keratinocytes increased ROS production, S-8 did not. Antioxidant pre-treatment blocked jet fuel induced immune suppression and cyclooxygenase-2 up-regulation. Accumulation of reactive oxygen species induces oxidant stress and affects activity of ROS sensitive transcription factors. JP-8 induced activation of NFκB while S-8 did not. Pre-treatment with antioxidants blocked activation of NFκB and parthenolide, an NFκB inhibitor, blocked jet fuel induced immune suppression and cyclooxygenase-2 expression in skin of treated mice. p65 siRNA transfected keratinocytes demonstrated NFκB is critically involved in jet fuel induced COX-2 expression. These findings clearly implicate the aromatic hydrocarbons found in jet fuel as the agents responsible for inducing immune suppression, in part by the production of reaction oxygen species, NFκB dependent up-regulation of cyclooxygenase-2, and the production of immune regulatory factors and cytokines. ^

Inflammatory Breast Cancer: The Immune Perspective

Inflammatory breast cancer (IBC) is the most insidious form of locally advanced disease. Although rare and less than 2% of all breast cancer, IBC is responsible for up to 10% of all breast cancer deaths. Despite the name, very little is known about the role of inflammation or immune mediators in IBC. Therefore, we analyzed blood samples from IBC patients and non-IBC patients, as well as healthy donor controls to establish an IBC-specific profile of peripheral blood leukocyte phenotype and function of T cells and dendritic cells and serum inflammatory cytokines. Emerging evidence suggests that host factors in the microenviromement may interact with underlying IBC genetics to promote the aggressive nature of the tumor. An integral part of the metastatic process involves epithelial to mesenchymal transition (EMT) where primary breast cancer cells gain motility and stem cell-like features that allow distant seeding. Interestingly, the IBC consortium microarray data found no clear evidence for EMT in IBC tumor tissues. It is becoming increasingly evident that inflammatory factors can induce EMT. However, it is unknown if EMT-inducing soluble factors secreted by activated immune cells in the IBC microenvironment canπ account for the absence of EMT in studies of the tumor cells themselves. We hypothesized that soluble factors from immune cells are capable of inducing EMT in IBC. We tested the ability of immune conditioned media to induce EMT in IBC cells. We found that soluble factors from activated immune cells are able to induce the expression of EMT-related factors in IBC cells along with increased migration and invasion. Specifically, the pro-inflammatory cytokines TNF-α, IL-6 and TGF-β were able to induce EMT and blocking these factors in conditioned media abated the induction of EMT. Surprisingly, unique to IBC cells, this process was related to increased levels of E-cadherin expression and adhesion, reminiscent of the characteristic tightly packed tumor emboli seen in IBC samples. This data offers insight into the unique pathology of IBC by suggesting that tumor immune interactions in the tumor microenvironment contribute to the aggressive nature of IBC implying that immune induced inflammation can be a novel therapeutic target. Specifically, we showed that soluble factors secreted by activated immune cells are capable of inducing EMT in IBC cells and may mediate the persistent E-cadherin expression observed in IBC. This data suggests that immune mediated inflammation may contribute to the highly aggressive nature of IBC and represents a potential therapeutic target that warrants further investigation.

The role of suppressor factors in the regulation of immune responses by ultraviolet radiation -induced suppressor T lymphocytes

The purpose of these studies was to determine the role of suppressor factors (TsF) in the regulation of immune responses by ultraviolet radiation-induced suppressor T lymphocytes (Ts). The Ts were induced following epicutaneous sensitization with contact allergens to an unirradiated site on mice irradiated five days earlier with 40 kJ/m$\sp2$ UVB (280-320 nm) radiation. The spleens of such mice contain afferent, hapten-specific, Thy-1$\sp+$, Lyt-1$\sp+$,2$\sp-$ Ts that suppress in vivo contact hypersensitivity (CHS) and antibody responses and the in vitro generation of cytotoxic T lymphocytes (CTL). Four approaches were used to determine the role of TsF. First, lysates produced from sonically-disrupted Ts were injected i.v. into normal animals; they inhibited CHS in vivo in a nonspecific manner. The lysates suppressed the induction and elicitation of CHS, and they inhibited the in vitro generation of CTL. Lysates prepared from splenocytes obtained from unirradiated mice or UV-irradiated, unsensitized mice failed to inhibit either response. Second, supernatants from cultures containing Ts, normal syngeneic responder lymphocytes, and hapten-modified stimulator cells were injected i.v. into normal recipients. They inhibited the induction of CHS and did so in a hapten-specific manner. Cellular and kinetic requirements were observed for the generation of suppressive activity. Splenocytes from mice treated with Ts supernatants suppressed CHS when transferred into normal animals. The supernatants also suppressed the in vitro generation of specific CTL. Third, the TsF-specific B16G monoclonal antibody was tested for its ability to modulate the effects of UV radiation in vivo. The i.v. injection of B16G into UV-irradiated mice reduced the suppression of CHS. Splenocytes of B16G-treated mice transferred into normal recipients, and they suppressed CHS, indicating that the Ts were not depleted. Fourth, B16G was used to isolate a putative TsF by antibody immunoadsorbance. When the B16G-bound fraction was eluted and injected i.v. into normal animals, it suppressed CHS and represented a 900-fold enrichment of activity over the starting material, based on specific activity. By SDS-PAGE, the B16G-bound material contained nondisulfide-linked 45- and 50-kDa components. These results suggest that TsF may play an immunoregulatory role in CHS. The isolation of a UV radiation-induced TsF lends credence to the involvement of such molecules. ^

Investigation of mechanisms involved in ultraviolet B radiation-induced, T cell -mediated immune suppression

Cutaneous exposure to ultraviolet-B radiation (UVR) results in the suppression of cell-mediated immune responses such as contact hypersensitivity (CHS) and delayed-type hypersensitivity (DTH). This modulation of immune responses is mediated by local or systemic mechanisms, both of which are associated with the generation of antigen-specific suppressor T lymphocytes (Ts). UV-induced Ts have been shown to be CD3+CD4+CD8 − T cells that control multiple immunological pathways. However, the precise mechanisms involved in the generation and function of these immunoregulatory cells remain unclear. We investigated the cellular basis for the generation of UV-induced Ts lymphocytes in both local and systemic models of immune suppression, and further examined the pleiotrophic function of these immunoregulatory cells. ^ We used Thy1.1 and Thy1.2 congenic mice in a draining lymph node (DLN) cell transfer model to analyze the role played by epidermal Langerhans cells in the generation of Ts cells. We demonstrate that T cells tightly adhered to antigen-presenting cells (APC) from UV-irradiated skin are the direct progenitors of UV-induced Ts lymphocytes. Our studies also reveal that UV-induced DNA-damage in the form of cyclobutyl pyrimidine dimers (CPD) in the epidermal APC is crucial for the altered maturation of these adherent T cells into Ts. ^ We used TCR transgenic mice in an adoptive transfer model and physically tracked the antigen-specific clones during immune responses in unirradiated versus UV-irradiated mice. We demonstrate that UV-induced Ts and effector TDTH cells share the same epitope specificity, indicating that both cell populations arise from the same clonal progenitors. UVR also causes profound changes in the localization and proliferation of antigen-specific T cells during an immune response. Antigen-specific T cells are not detectable in the DLNs of UV-irradiated mice after 3 days post-immunization, but are found in abundance in the spleen. In contrast, these clones continue to be found in the DLNs and spleens of normal animals several days post-immunization. Our studies also reveal that a Th2 cytokine environment is essential for the generation of Ts in UV-irradiated mice. ^ The third part of our study examined the pleiotrophic nature of UV-induced Ts. We used a model for the induction of both cellular and humoral responses to human gamma-globulin (HGG) to demonstrate that UV-induced Ts lymphocytes can suppress DTH as well as antibody responses. (Abstract shortened by UMI.) ^

The role of p53 in skin cancer induction by UV radiation and as a potential tumor antigen in UV-induced murine skin tumors

Carcinoma of the skin is the most common type of human cancer in the United States. Ultraviolet radiation (UVR) present in the sunlight is thought to be the major carcinogen responsible for induction of skin cancer. In UV-associated skin carcinogenesis, mutations in p53 are not only present with very high frequency, but occur early in the course of tumor development. In addition, UV-induced skin tumors in mice exhibit unique immunological characteristics. They are highly antigenic and express both individually-specific tumor transplantation antigens recognized by effector T cells and the UV-associated common antigen recognized by UV-induced suppressor T cells. ^ To examine the hypothesis that p53 plays a critical role in preventing skin cancer induction by UVR, mice constitutively lacking one or two functional p53 alleles were compared to wild-type mice for their susceptibility to UV carcinogenesis. Both p53 +/– and –/– mice showed greater susceptibility to skin cancer induction than wild-type mice, and –/– mice were the most susceptible, Accelerated tumor development in the p53 +/– mice was not associated with loss of the remaining wild-type allele of p53 , but in many cases was associated with UV-induced mutations in p53. Our studies clearly demonstrate the essential role of p53 in protection against UV carcinogenesis, particularly in the eye and epidermis. ^ The role of p53 in the antigenicity of UV-induced murine skin tumors was also addressed. Primary UV-induced tumors from p53 –/–, +/– and +/+ mice were transplanted into both normal and immunosuppressed mice, and rates of tumor rejection were compared. Tumors from mice with only one or no functional p53 alleles were less antigenic than those from mice with two functional p53 alleles. Moreover, tumors with no functional p53 also failed to grow well in chronically UV-irradiated mice. These results indicate that p53 contributes to the strong antigenicity of UV-induced murine skin tumors, and suggest that it may play a critical role in expression of the UV-associated common antigen recognized by suppressor T cells. ^ In this study we also monitored the effect of UVR on the development of lymphoid malignancies in p53 deficient mice. The incidence of lymphoid malignancies in UV-irradiated p53 +/– mice was drastically enhanced compared to that in unirradiated counterparts. The immune responses of the mice were identical and were suppressed to the same extent by UV irradiation regardless of the p53 genotype. These data provide the first experimental evidence that exposure to UVR can contribute to the development of lymphoid neoplasms in genetically susceptible hosts. ^

Ultraviolet radiation modulates the immune system through the platelet -activating factor receptor

Ultraviolet radiation plays a critical role in the induction of non-melanoma skin cancer. UV radiation is also immune suppressive. Moreover, UV-induced systemic immune suppression is a major risk factor for skin cancer induction. Previous work had shown that UV exposure in vivo activates a cytokine cascade involving PGE2, IL-4, and IL-10 that induces immune suppression. However, the earliest molecular events that occur immediately after UV-exposure, especially those upstream of PGE2, were not well defined. To determine the initial events and mediators that lead to immune suppression after a pathological dose of UV, mouse keratinocytes were analyzed after sunlamp irradiation. It is known that UV-irradiated keratinocytes secrete the phospholipid mediator of inflammation, platelet-activating factor (PAF). Since PAF stimulates the production of immunomodulatory compounds, including PGE2, the hypothesis that UV-induced PAF activates cytokine production and initiates UV-induced immune suppression was tested. Both UV and PAF activated the transcription of cyclooxygenase (COX)-2 and IL-10 reporter gene constructs. A PAF receptor antagonist blocked UV-induced IL, 10 and COX-2 transcription. PAF mimicked the effects of UV in vivo and suppressed delayed-type hypersensitivity (DTH), and immune suppression was blocked when UV-irradiated mice were injected with a PAF receptor antagonist. This work shows that UV generates PAF-like oxidized lipids, that signal through the PAF receptor, activate cytokine transcription, and induce systemic immune suppression. ^

Immune Polarization in Allergic Patients: Role of the Innate Immune System

Allergens come into contact with the immune system as components of a very diverse mixture. The most common sources are pollen grains, food, and waste. These sources contain a variety of immunomodulatory components that play a key role in the induction of allergic sensitization. The way allergen molecules bind to the cells of the immune system can determine the immune response. In order to better understand how allergic sensitization is triggered, we review the molecular mechanisms involved in the development of allergy and the role of immunomodulators in allergen recognition by innate cells.

Immunomodulation of experimental autoimmune encephalomyelitis by oral administration of copolymer 1

The activity of copolymer 1 (Cop 1, Copaxone, glatiramer acetate) in suppressing experimental autoimmune encephalomyelitis (EAE) and in the treatment of multiple sclerosis patients when injected parenterally has been extensively demonstrated. In the present study we addressed the question of whether Cop 1 can induce oral tolerance to EAE similar to myelin basic protein (MBP). We now have demonstrated that oral Cop 1 inhibited EAE induction in both rats and mice. Furthermore, oral Cop 1 was more effective than oral MBP in suppressing EAE in rats. The beneficial effect of oral Cop 1 was found to be associated with specific inhibition of the proliferative and Th1 cytokine secretion responses to MBP of spleen cells from Cop 1-fed mice and rats. In all of these assays, oral Cop 1 was more effective than oral MBP. The tolerance induced by Cop 1 could be adoptively transferred with spleen cells from Cop 1-fed animals. Furthermore, Cop 1-specific T cell lines, which inhibit EAE induction in vivo, could be isolated from the above spleen cells. These T cell lines secrete the anti-inflammatory cytokines IL-10 and transforming growth factor type β, but not IL-4, in response to both Cop 1 and MBP. In conclusion, oral Cop 1 has a beneficial effect on the development of EAE that is associated with down-regulation of T cell immune responses to MBP and is mediated by Th2/3 type regulatory cells. These results suggest that oral administration of Cop 1 may modulate multiple sclerosis as well.

CD8 T cell ignorance or tolerance to islet antigens depends on antigen dose

There are two major mechanisms reported to prevent the autoreactivity of islet-specific CD8+ T cells: ignorance and tolerance. When ignorance is operative, naïve autoreactive CD8+ T cells ignore islet antigens and recirculate without causing damage, unless activated by an external stimulus. In the case of tolerance, CD8+ T cells are deleted. Which factor(s) contributes to each particular outcome was previously unknown. Here, we demonstrate that the concentration of self antigen determines which mechanism operates. When ovalbumin (OVA) was expressed at a relatively low concentration in the pancreatic islets of transgenic mice, there was no detectable cross-presentation, and the CD8+ T cell compartment remained ignorant of OVA. In mice expressing higher doses of OVA, cross-presentation was detectable and led to peripheral deletion of OVA-specific CD8+ T cells. When cross-presentation was prevented by reconstituting the bone marrow compartment with cells incapable of presenting OVA, deletional tolerance was converted to ignorance. Thus, the immune system uses two strategies to avoid CD8+ T cell-mediated autoimmunity: for high dose antigens, it deletes autoreactive T cells, whereas for lower dose antigens, it relies on ignorance.

Precursor B cells for autoantibody production in genomically Fas-intact autoimmune disease are not subject to Fas-mediated immune elimination

The Fas/Fas ligand (FasL) system participates in regulation of the immune system through the apoptotic process. However, the extent to which abnormalities in this system are involved in the loss of self-tolerance and development of autoimmune disease not associated with Fas/FasL mutations remains unknown. The present study addresses this issue in Fas/FasL-intact, systemic lupus erythematosus (SLE)-prone (NZB × NZW) (NZB/W) F1 mice. While splenic B cells from 2-month-old mice before overt SLE expressed Fas poorly, in vitro stimulation with an agonistic anti-CD40 mAb up-regulated their Fas expression, thus revealing the existence of two populations: one was Fashigh and highly susceptible to anti-Fas mAb-induced apoptosis, and the other was Faslow and apoptosis-resistant. The Faslow cells were included in the CD5+ B cell subpopulation and contained most of the cells that produced IgM anti-DNA antibodies. The isotype of anti-DNA antibodies switches from IgM to IgG in NZB/W F1 mice at ages beginning at about 6 months. These IgG anti-DNA antibodies were produced almost exclusively by a subpopulation of splenic B cells that spontaneously expressed low levels of Fas in vivo and were apoptosis-resistant. The findings indicate that precursor B cells for autoantibody production and presumably autoantibody-secreting cells in these mice are relatively resistant to Fas-mediated apoptosis, a finding supporting the concept that abnormalities of Fas-mediated apoptotic process are involved in the development of autoreactive B cells in Fas/FasL-intact autoimmune disease.

Immunologic tolerance to myelin basic protein decreases stroke size after transient focal cerebral ischemia

Immune mechanisms contribute to cerebral ischemic injury. Therapeutic immunosuppressive options are limited due to systemic side effects. We attempted to achieve immunosuppression in the brain through oral tolerance to myelin basic protein (MBP). Lewis rats were fed low-dose bovine MBP or ovalbumin (1 mg, five times) before 3 h of middle cerebral artery occlusion (MCAO). A third group of animals was sensitized to MBP but did not survive the post-stroke period. Infarct size at 24 and 96 h after ischemia was significantly less in tolerized animals. Tolerance to MBP was confirmed in vivo by a decrease in delayed-type hypersensitivity to MBP. Systemic immune responses, characterized in vitro by spleen cell proliferation to Con A, lipopolysaccharide, and MBP, again confirmed antigen-specific immunologic tolerance. Immunohistochemistry revealed transforming growth factor β1 production by T cells in the brains of tolerized but not control animals. Systemic transforming growth factor β1 levels were equivalent in both groups. Corticosterone levels 24 h after surgery were elevated in all sham-operated animals and ischemic control animals but not in ischemic tolerized animals. These results demonstrate that antigen-specific modulation of the immune response decreases infarct size after focal cerebral ischemia and that sensitization to the same antigen may actually worsen outcome.

Molecular immune responses of the mosquito Anopheles gambiae to bacteria and malaria parasites

Immune responses of the malaria vector mosquito Anopheles gambiae were monitored systematically by the induced expression of five RNA markers after infection challenge. One newly isolated marker encodes a homologue of the moth Gram-negative bacteria-binding protein (GNBP), and another corresponds to a serine protease-like molecule. Additional previously described markers that respond to immune challenge encode the antimicrobial peptide defensin, a putative galactose lectin, and a putative serine protease. Specificity of the immune responses was indicated by differing temporal patterns of induction of specific markers in bacteria-challenged larvae and adults, and by variations in the effectiveness of different microorganisms and their components for marker induction in an immune-responsive cell line. The markers exhibit spatially distinct patterns of expression in the adult female mosquito. Two of them are highly expressed in different regions of the midgut, one in the anterior and the other in the posterior midgut. Marker induction indicates a significant role of the midgut in insect innate immunity. Immune responses to the penetration of the midgut epithelium by a malaria parasite occur both within the midgut itself and elsewhere in the body, suggesting an immune-related signaling process.

Induction of inhibitory factor κBα mRNA in the central nervous system after peripheral lipopolysaccharide administration: An in situ hybridization histochemistry study in the rat

In this study we investigate the mRNA expression of inhibitory factor κBα (IκBα) in cells of the rat brain induced by an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS). IκB controls the activity of nuclear factor κB, which regulates the transcription of many immune signal molecules. The detection of IκB induction, therefore, would reveal the extent and the cellular location of brain-derived immune molecules in response to peripheral immune challenges. Low levels of IκBα mRNA were found in the large blood vessels and in circumventricular organs (CVOs) of saline-injected control animals. After an i.p. LPS injection (2.5 mg/kg), dramatic induction of IκBα mRNA occurred in four spatio-temporal patterns. Induced signals were first detected at 0.5 hr in the lumen of large blood vessels and in blood vessels of the choroid plexus and CVOs. Second, at 1–2 hr, labeling dramatically increased in the CVOs and choroid plexus and spread to small vascular and glial cells throughout the entire brain; these responses peaked at 2 hr and declined thereafter. Third, cells of the meninges became activated at 2 hr and persisted until 12 hr after the LPS injection. Finally, only at 12 hr, induced signals were present in ventricular ependyma. Thus, IκBα mRNA is induced in brain after peripheral LPS injection, beginning in cells lining the blood side of the blood–brain barrier and progressing to cells inside brain. The spatiotemporal patterns suggest that cells of the blood–brain barrier synthesize immune signal molecules to activate cells inside the central nervous system in response to peripheral LPS. The cerebrospinal fluid appears to be a conduit for these signal molecules.

Induction of maturation of human blood dendritic cell precursors by measles virus is associated with immunosuppression

As well as inducing a protective immune response against reinfection, acute measles is associated with a marked suppression of immune functions against superinfecting agents and recall antigens, and this association is the major cause of the current high morbidity and mortality rate associated with measles virus (MV) infections. Dendritic cells (DCs) are antigen-presenting cells crucially involved in the initiation of primary and secondary immune responses, so we set out to define the interaction of MV with these cells. We found that both mature and precursor human DCs generated from peripheral blood monocytic cells express the major MV protein receptor CD46 and are highly susceptible to infection with both MV vaccine (ED) and wild-type (WTF) strains, albeit with different kinetics. Except for the down-regulation of CD46, the expression pattern of functionally important surface antigens on mature DCs was not markedly altered after MV infection. However, precursor DCs up-regulated HLA-DR, CD83, and CD86 within 24 h of WTF infection and 72 h after ED infection, indicating their functional maturation. In addition, interleukin 12 synthesis was markedly enhanced after both ED and WTF infection in DCs. On the other hand, MV-infected DCs strongly interfered with mitogen-dependent proliferation of freshly isolated peripheral blood lymphocytes in vitro. These data indicate that the differentiation of effector functions of DCs is not impaired but rather is stimulated by MV infection. Yet, mature, activated DCs expressing MV surface antigens do give a negative signal to inhibit lymphocyte proliferation and thus contribute to MV-induced immunosuppression.

Immune response to a differentiation antigen induced by altered antigen: A study of tumor rejection and autoimmunity

Recognition of self is emerging as a theme for the immune recognition of human cancer. One question is whether the immune system can actively respond to normal tissue autoantigens expressed by cancer cells. A second but related question is whether immune recognition of tissue autoantigens can actually induce tumor rejection. To address these issues, a mouse model was developed to investigate immune responses to a melanocyte differentiation antigen, tyrosinase-related protein 1 (or gp75), which is the product of the brown locus. In mice, immunization with purified syngeneic gp75 or syngeneic cells expressing gp75 failed to elicit antibody or cytotoxic T-cell responses to gp75, even when different immune adjuvants and cytokines were included. However, immunization with altered sources of gp75 antigen, in the form of either syngeneic gp75 expressed in insect cells or human gp75, elicited autoantibodies to gp75. Immunized mice rejected metastatic melanomas and developed patchy depigmentation in their coats. These studies support a model of tolerance maintained to a melanocyte differentiation antigen where tolerance can be broken by presenting sources of altered antigen (e.g., homologous xenogeneic protein or protein expressed in insect cells). Immune responses induced with these sources of altered antigen reacted with various processed forms of native, syngeneic protein and could induce both tumor rejection and autoimmunity.