A sensitive two-site enzyme immunoassay for the detection of rat interferon-gamma in biological fluids

Supramolecular Conjugated Polymer Systems with Controlled Antibacterial Activity

Infections of antibiotic-resistant pathogens have caused a series of public health crises across the world. According to the latest published reports, an antibiotic switch has been recognized as a potential strategy to control antibacterial activity for combating this serious drug resistance. Thus, it is anticipated that more effective antibiotic switches should be obtained by further exploring the developed strategies. Here, we report an improved pretreatment strategy using a surfactant (Triton X-100) for constructing an effective supramolecular antibiotic switch based on a poly(fluorene-co-phenylene) derivative (PFP) and cucurbit[7]uril (CB[7]), which can regulate the aggregation state of polymers before the supramolecular self-assembly process occurs. Triton X-100 can regulate the aggregation states of conjugated polymers, which is used to successfully realize the reversible control of bactericidal activity of PFP in the dark and under white light irradiation by supramolecular assembly/disassembly between PFP and CB[7]. Specialized antibiotic switches are significantly important to fight pathogenic infections and solve the drug resistance crisis in the future.

Decreased availability of intestinal dopamine in transmural colitis may relate to inhibitory effects of interferon-gamma upon L-DOPA uptake

AIMS

The present study aimed to evaluate the relationship between intestinal inflammation, interferon-gamma (IFN-gamma) levels and intestinal levels of dopamine, its precursor l-3,4-dihydroxyphenylalanine (L-DOPA), and the activity of aromatic L-amino acid decarboxylase (AADC) activity along the digestive tract in a rat experimental model of colitis.

METHODS

Colitis was induced by rectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS). Catechol derivatives were assayed by means of HPLC-EC.

RESULTS

It is shown that dopamine and noradrenaline levels in the distal colon (inflamed mucosa), but not in the ileum (non-inflamed mucosa), of TNBS-treated rats were markedly lower than in control animals. A slight decrease in L-DOPA tissue levels, no changes in AADC activity and an increase in plasma IFN-gamma levels accompanied this decrease in dopamine levels. Exposure of Caco-2 cells, a human intestinal epithelial cell line, to human IFN-gamma resulted in a concentration-dependent and long-lasting inhibition of L-DOPA uptake, which most likely explains the decrease in dopamine levels in the inflamed mucosa.

CONCLUSION

Changes in tissue levels of noradrenaline and dopamine in experimental colitis in the rat follow a similar pattern to that observed in patients with Crohn's disease and ulcerative colitis. In this model of experimental colitis, the decrease in dopamine levels is most likely explained by the inhibitory effect of IFN-gamma on L-DOPA uptake by intestinal epithelial cells.

Differential modulation of CD8beta by rat gammadelta and alphabeta T cells after activation

Major histocompatibility complex (MHC) class I-restricted alphabeta T cells express the CD8alphabeta heterodimer, which acts as a MHC class I-specific co-receptor. Rats are so far the only species with frequent expression of the CD8alphabeta by MHC-unrestricted gammadelta T cells. This study compares CD8alphabeta expression by splenic rat alphabeta and gammadelta T cells and reveals a lineage-specific difference in the control of CD8beta expression. After activation in vitro, many gammadelta T cells, but not alphabeta T cells, persistently down-modulate the expression of CD8beta, but not CD8alpha, at the RNA level. Down-regulation occurred after stimulation with T-cell receptor (TCR)-specific monoclonal antibody (mAb) and interleukin-2 (IL-2) or CD28-mediated costimulation, and after activation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. Functional differences between modulating and non-modulating cells were not found with respect to interferon-gamma (IFN-gamma) production and cytolytic activity. The modulation could be indicative for a fundamental difference between alphabeta and gammadelta T cells and also limits the use of CD8beta as a stable marker of gammadelta T-cell subsets. Possibly, CD8beta modulation provides a mechanism to escape over-stimulation by (auto-)antigens by increasing the threshold of TCR-mediated activation in gammadelta T cells.

Apomorphine-susceptible and apomorphine-unsusceptible Wistar rats differ in their susceptibility to inflammatory and infectious diseases: a study on rats with group-specific differences in structure and reactivity of hypothalamic-pituitary-adrenal axis

Variability in susceptibility to diseases is a well known phenomenon that has been attributed to genetic and environmental factors. At the level of the immune system, the reactivity of two types of T helper cells (Th1 and Th2 cells) plays an important role in determining disease susceptibility. Inflammatory (autoimmune) diseases are stimulated by cytokines produced by Th1 cells. Th2 cytokines stimulate antibody production (e.g., IgE) and eosinophilia as observed in allergic reactions or during parasitic infections. We describe here that the reactivity in a Th1 or a Th2 disease model significantly differs between individual rats that show group-specific differences in reactivity of the hypothalamic-pituitary-adrenal (HPA) axis, as well as in their behavioral responses to stress. We used two outbred lines of Wistar rats, apomorphine-susceptible rats that have a relatively hyperreactive HPA axis (APO-SUS) and apomorphine-unsusceptible rats that have a relatively hyporeactive HPA axis (APO-UNSUS). APO-SUS, but not APO-UNSUS, rats generated a vigorous, Th2-dependent IgE response after infection with the nematode Trichinella spiralis. In contrast, APO-UNSUS, but not APO-SUS, rats were susceptible for Th1-mediated experimental autoimmune encephalomyelitis. Investigation of cytokine responses of splenocytes revealed that the ratio of mRNA expression for Th1-derived interferon (IFN)-gamma and mRNA expression of Th2-derived interleukin-4 (IL-4) was significantly smaller in APO-SUS than in APO-UNSUS rats. In conclusion, individual differences in structure and reactivity of the neuroendocrine system co-occur with group-specific differences in susceptibility to inflammatory and infectious diseases.

Expression of interferons-alpha and -gamma in testicular interstitial tissue and spermatogonia of the rat

The testis is divided into two compartments: the seminiferous tubules and the interstitial tissue. The latter essentially consists of the blood and lymphatic vessels, testosterone-producing Leydig cells, and testicular macrophages. In the exploration of the testicular antiviral defense system, we initially searched for interferon (IFN) production by the seminiferous tubule cells. The site of virus entry into the testis is probably the interstitial compartment; thus, it is important to know whether and how the cells in this compartment are protected against viral infection. In addition, as germ cell precursors (spermatogonia) are only partially protected by the blood-testis barrier, it was important to explore the antiviral capability of these cells. In this study we searched for IFN production by Leydig cells, testicular macrophages, and spermatogonia after exposure to Sendai virus. We also investigated the effect of viral exposure on testosterone production by Leydig cells. Our results show that spermatogonia do not constitutively express IFNs and give a very poor response to the virus. In contrast, testicular macrophages constitutively produced type I IFNs, and this production was markedly stimulated by Sendai virus. Leydig cells produced twice as much type I IFNs as testicular macrophages after viral exposure, and they were the only cells producing both IFNalpha and -gamma, with these IFNs being dramatically induced/ increased in response to exposure to the virus. Furthermore, incubation of Leydig cells with the Sendai virus stimulated testosterone production. In conclusion, this study further establishes the topography of IFN expression within the testis. This allows us to hypothesize that the potential antiviral system represented by Leydig cells and, to a lesser extent, by macrophages plays a key role in protecting both androgen production and spermatogenesis.

The extracellular matrix: an early target of preservation/reperfusion injury and acute rejection after small bowel transplantation

BACKGROUND

Endothelial cells are known to be an early target of preservation/reperfusion injury and acute rejection, whereas the extracellular matrix (ECM) may also play an equally important role in the sequelae of both events.

METHODS

Syngeneic and allogeneic rat small bowel transplantations (SBTX) were performed after 6 hr of preservation. Animals were subsequently killed at defined time points for determination of ECM parameters within the graft and in plasma.

RESULTS

Laminin levels were significantly increased 20 min after reperfusion (syngeneic SBTX: 357+/-65.9 ng/ml; allogeneic SBTX: 361+/-79.6 ng/ml; P< or =0.01). After syngeneic transplantation, laminin levels normalized by postoperative day (POD) 7, whereas there was a rejection-induced increase after allogeneic SBTX (POD 7: 179+/-60.1 ng/ml; POD 9: 333+/-13.6 ng/ml; P< or =0.01 vs. syngeneic SBTX). This increase was accompanied by an increase in tumor necrosis factor-alpha levels at POD 9. Hyaluronic acid levels were significantly elevated after 24 hr (syngeneic SBTX: 1086+/-176 microg/L; allogeneic SBTX: 918+/-108 microg/L; P< or =0.01). After syngeneic SBTX, hyaluronic acid levels normalized by POD 7, whereas persistently higher levels were observed after allogeneic SBTX. Immunohistochemistry confirmed early changes (20 min after reperfusion) at the ECM. Anti-laminin and anti-CD44 staining normalized at POD 5 after syngeneic SBTX. After allogeneic SBTX, rejection-specific changes were evident with anti-laminin staining commencing on POD 5 and progressing until POD 9. At similar time points, increased expression of fibronectin- and interferon-gamma-positive material was evident.

CONCLUSIONS

The ECM can be considered to be an early target of preservation/reperfusion injury and acute rejection. Plasma parameters reliably reflected the changes observed within the graft. Laminin and hyaluronic acid levels may be used as indicators of initial graft function. Furthermore, the increase in laminin levels was an early indicator of acute rejection. Determination of these parameters may significantly improve monitoring after SBTX.

In vitro effects of melatonin on mitogen-induced lymphocyte proliferation and cytokine expression in young and old rats

Melatonin (MLT) treatment in vivo has been shown to have immunomodulatory and anti-immunosenescent effects in the mouse model. In the present report, the in vitro effect of MLT on mitogen-induced lymphocyte proliferation and cytokine expression was evaluated in a rat model. Splenic lymphocytes were isolated from young (6 months) and old (24 months) F344 rats and were incubated with MLT in the presence or absence of mitogens. The proliferative response to concanavalin A (ConA) or PMA plus ionomycin was measured in splenocytes or T cells isolated from young and old rats. In addition, the induction of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production was measured in MLT-treated and untreated lymphocytes isolated from young and old rats. The ConA-induced lymphocyte proliferation and IL-2 expression were significantly lower and induction of IFN-gamma production was significantly higher in splenocytes and purified T cells isolated from old rats compared to splenocytes and T cells isolated from young rats. Treatment of lymphocytes with MLT did not significantly alter ConA-induced lymphocyte proliferation or IL-2 or IFN-gamma expression in lymphocytes isolated from either young or old rats. On the basis of these data, we conclude that in vitro MLT treatment had no immunomodulatory effect on lymphocytes from rats.

Regulation of T-cell activation in the lung: alveolar macrophages induce reversible T-cell anergy in vitro associated with inhibition of interleukin-2 receptor signal transduction

Alveolar macrophages (AM) are recognized as archetypal 'activated' macrophages with respect to their capacity to suppress T-cell responses to antigen or mitogen, and this function has been ascribed an important role in the maintenance of local immunological homeostasis at the delicate blood:air interface. The present study demonstrates that this suppression involves a unique form of T-cell anergy, in which 'AM-suppressed' T cells proceed normally through virtually all phases of the activation sequence including Ca2+ flux, T-cell receptor (TCR) modulation, cytokine [including interleukin-2 (IL-2)] secretion and IL-2 receptor (IL-2R) expression. However, the 'suppressed' T cells fail to up-regulate CD2, and do not re-express normal levels of TCR-associated molecules after initial down-modulation; moreover, they are unable to transduce IL-2 signals leading to phosphorylation of IL-2R-associated proteins, and remained locked in G0/G1. The induction of this form of anergy is blocked by an NO-synthase inhibitor, and is reversible upon removal of AM from the T cells, which then proliferate in the absence of further stimulation. We hypothesize that this mechanism provides the means to limit the magnitude of local immune responses in this fragile tissue microenvironment, while preserving the capacity for generation of immunological memory against locally encountered antigens via clonal expansion of activated T cells after their subsequent migration to regional lymphoid organs. In an accompanying paper, we demonstrate that a significant proportion of T cells freshly isolated from lung exhibit a comparable surface phenotype.

Effect of dehydroepiandrosterone on mitogen-induced lymphocyte proliferation and cytokine production in young and old F344 rats

The steroid hormone intermediate, dehydroepiandrosterone (DHEA), has been proposed as a therapeutic agent for the treatment of immunosenescence in mouse model. In the present study, the in vitro effect of DHEA on mitogen-induced lymphocyte proliferation and cytokine production was evaluated in a rat model. Spleen lymphocytes were isolated from young (4-6 months) and old (24-26 months) F344 rats and were incubated with DHEA for 30 min. The induction of lymphocyte proliferation, interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) production by concanavalin A (Con A) was measured in a culture medium supplemented with either fetal calf serum (FCS) or with serum-free medium (Nutridoma-SR, N-SR). The induction of lymphocyte proliferation and IL-2 production by Con A decreased significantly with age, whereas induction of IFN-gamma increased with age. Treatment of lymphocytes with DHEA did not significantly alter Con A-induced proliferation or the production of IL-2 or IFN-gamma by spleen lymphocytes isolated from either young or old rats. These data indicate that in vitro DHEA treatment appears to have no immunomodulatory effect on the age-related changes in mitogen-induced proliferation or cytokine production in rat lymphocytes.

The natural immune response to inhaled soluble protein antigens involves major histocompatibility complex (MHC) class I-restricted CD8+ T cell-mediated but MHC class II-restricted CD4+ T cell-dependent immune deviation resulting in selective suppression of immunoglobulin E production

The immunological basis for atopy is currently ascribed to an inherent bias in the CD4+ T cell response to nonreplicating antigens presented at mucosal surfaces, resulting in dominance of the T helper 2 (Th2) interleukin 4 (IL-4)-producing phenotype, which favors IgE production. In contrast, the "normal" response to such antigens involves a predominance of interferon gamma (IFN-gamma)-producing Th1 clones. This difference has been suggested to be the result of active selection in atopics for Th2 (and hence against Th1) clones at the time of initial antigen presentation. In the study below, we demonstrate that the natural immune response to inhaled protein antigens, particularly in animals expressing the low immunoglobulin E (IgE) responder phenotype, includes a major histocompatibility complex (MHC) class I-restricted CD8+ T cell component, the appearance of which is associated with active suppression of IgE antibody production. Thus, continued exposure of rats to aerosolized ovalbumin (OVA) antigen elicits a transient IgE response, that is terminated by the onset of a state of apparent "tolerance" to further challenge, and this tolerant state is transferable to naive animals with CD8+ T cells. Kinetic studies on in vitro T cell reactivity in these aerosol-exposed rats demonstrated biphasic CD4+ Th2 responses which terminated, together with IgE antibody production, and coincident with the appearance of MHC class I-restricted OVA-specific IFN-gamma-producing CD8+ T cells. However, the latter were not autonomous in vitro and required a source of exogenous IL-2 for initial activation, which in CD(8+)-enriched splenocyte cultures could be provided by small numbers of contaminating OVA-specific CD4+ T cells. This represents the first formal evidence for the induction of an MHC class I-restricted T cell response to natural mucosal exposure to an inert protein antigen, and is consistent with a growing literature demonstrating sensitization of MHC class I-restricted CD8+ T cells by deliberate immunization with soluble proteins. We suggest that crossregulation of MHC class II-restricted CD4+ T cells via cytokine signals generated in parallel CD8+ T cell responses represents a covert and potentially important selection pressure that can shape the nature of host responses to nonreplicating antigens presented at mucosal surfaces.

Complement-mediated inactivation of interferon-gamma in ELISA systems

The recovery of a predetermined amount of interferon-gamma (IFN-gamma) added to normal serum was studied in two independent sandwich ELISA systems specific for rat and human IFN-gamma. In both assays the ELISA activity was rapidly lost in fresh but not in heat-inactivated (30', 56 degrees C) serum. Ninety percent of the initial activity had disappeared within 30 minutes upon incubation at 37 degrees C. Serum-mediated inhibition was not species-specific as the ELISA activity of rat IFN-gamma diminished equally well in rat and human sera. Inhibition was critically dependent on the isotype of the solid-phase monoclonal antibody (mAb) used in the ELISA systems. IgG1 and IgG2a mAbs efficiently inhibited the ELISA activity of IFN-gamma, whereas an IgA mAb was ineffective. The inhibition was not influenced by a wide variety of anti-proteolytic agents but was effectively blocked by anti-complementary substances or treatments directed to the first (C1) and third (C3) component of complement. Our results indicate that activation of the classical pathway of complement (CPC) and the concomitant covalent binding of C3 to the IFN-gamma molecule play a major role in the inhibitory process. It is concluded that reduction of the ELISA activity is attributable to diminished accessibility of the detector antibody for the IFN-gamma protein as a consequence of C3 binding.