Vasoactive intestinal peptide stimulates T lymphocytes to release IL-5 in murine schistosomiasis mansoni infection.

In murine schistosomiasis, granulomas form around ova deposited in the liver and intestines of infected mice. The granulomas have eosinophils that produce vasoactive intestinal peptide (VIP) and T cells that display VIP receptors. IL-5 is a lymphokine important for the development and maturation of eosinophils. It seemed plausible that VIP, released from eosinophils, may interact with lymphocyte VIP receptors and modulate IL-5 production as part of a feedback regulatory circuit. Thus, we determined whether granuloma T cells make IL-5 and whether VIP modulates IL-5 production. Isolated granuloma cells enriched for T lymphocytes spontaneously released IL-5. Culture of these cells in the presence of VIP increased IL-5 secretion. Spleen cells were also studied. Spleen cells from infected mice did not spontaneously release IL-5 or express IL-5 mRNA and VIP did not stimulate these resting spleen cells to produce this IL. However, these cells did express IL-5 mRNA and secreted IL-5 in response to Con A or soluble egg Ag. VIP could not appreciably modulate IL-5 release when cells were cultured with VIP and the Ag or mitogen. Spleen cells washed free of Con A ceased IL-5 secretion within 24 h. These preactivated splenic T cells resumed vigorous IL-5 secretion in response to either Con A or VIP. Yet only Con A prominently induced IL-5 mRNA expression. VIP was an effective stimulus at concentrations equal to or above the kDa of the VIP receptor on both splenic and granuloma T cells (10(-8) M). It is concluded that, in murine schistosomiasis, VIP invokes IL-5 release from activated T cells that are not undergoing immediate TCR stimulation.     

Infection of human macrophages and dendritic cells with Mycobacterium tuberculosis induces a differential cytokine gene expression that modulates T cell response

Macrophages and dendritic cells (DC) play an essential role in the initiation and maintenance of immune response to pathogens. To analyze early interactions between Mycobacterium tuberculosis (Mtb) and immune cells, human peripheral blood monocyte-derived macrophages (MDM) and monocyte-derived dendritic cells (MDDC) were infected with Mtb. Both cells were found to internalize the mycobacteria, resulting in the activation of MDM and maturation of MDDC as reflected by enhanced expression of several surface Ags. After Mtb infection, the proinflammatory cytokines TNF-alpha, IL-1, and IL-6 were secreted mainly by MDM. As regards the production of IFN-gamma-inducing cytokines, IL-12 and IFN-alpha, was seen almost exclusively from infected MDDC, while IL-18 was secreted preferentially by macrophages. Moreover, Mtb-infected MDM also produce the immunosuppressive cytokine IL-10. Because IL-10 is a potent inhibitor of IL-12 synthesis from activated human mononuclear cells, we assessed the inhibitory potential of this cytokine using soluble IL-10R. Neutralization of IL-10 restored IL-12 secretion from Mtb-infected MDM. In line with these findings, supernatants from Mtb-infected MDDC induced IFN-gamma production by T cells and enhanced IL-18R expression, whereas supernatants from MDM failed to do that. Neutralization of IFN-alpha, IL-12, and IL-18 activity in Mtb-infected MDDC supernatants by specific Abs suggested that IL-12 and, to a lesser extent, IFN-alpha and IL-18 play a significant role in enhancing IFN-gamma synthesis by T cells. During Mtb infection, macrophages and DC may have different roles: macrophages secrete proinflammatory cytokines and induce granulomatous inflammatory response, whereas DC are primarily involved in inducing antimycobacterial T cell immune response.     

Plasmacytoid dendritic cells take up opsonized antigen leading to CD4+ and CD8+ T cell activation in vivo

Plasmacytoid dendritic cells (pDC) are the body's main source of IFN-alpha, but, unlike classical myeloid DC (myDC), they lack phagocytic activity and are generally perceived as playing only a minor role in Ag processing and presentation. We show that murine pDC, as well as myDC, express Fcgamma receptors (CD16/CD32) and can use these receptors to acquire Ag from immune complexes (IC), resulting in the induction of robust Ag-specific CD4(+) and CD8(+) T cell responses. IC-loaded pDC stimulate CD4(+) T cells to proliferate and secrete a mixture of IL-4 and IFN-gamma, and they induce CD8(+) T cells to secrete IL-10 as well as IFN-gamma. In contrast, IC-loaded myDC induce both CD4(+) and CD8(+) T cells to secrete mainly IFN-gamma. These results indicate that pDC can shape an immune response by acquiring and processing opsonized Ag, leading to a predominantly Th2 response.     

Partial IL-10 inhibition of the cell-mediated immune response in chronic beryllium disease.

Chronic beryllium disease (CBD) provides a human disorder in which to study the delayed type IV hypersensitivity response to persistent Ag that leads to noncaseating pulmonary granuloma formation. We hypothesized that, in CBD, failure of IL-10 to modulate the beryllium-specific, cell-mediated immune response would result in persistent, maximal cytokine production and T lymphocyte proliferation, thus contributing to the development of granulomatous lung disease. To test this hypothesis, we used bronchoalveolar lavage cells from control and CBD subjects to evaluate the beryllium salt-specific production of endogenous IL-10 and the effects of exogenous human rIL-10 (rhIL-10) on HLA expression, on the production of IL-2, IFN-gamma, and TNF-alpha, and on T lymphocyte proliferation. Our data demonstrate that beryllium-stimulated bronchoalveolar lavage cells produce IL-10, and the neutralization of endogenous IL-10 does not increase significantly cytokine production, HLA expression, or T lymphocyte proliferation. Second, the addition of excess exogenous rhIL-10 partially inhibited the beryllium-stimulated production of IL-2, IFN-gamma, and TNF-alpha; however, we measured no change in T lymphocyte proliferation or in the percentage of alveolar macrophages expressing HLA-DP. Interestingly, beryllium salts interfered with an IL-10-stimulated decrease in the percentage of alveolar macrophages expressing HLA-DR. We conclude that, in the CBD-derived, beryllium-stimulated cell-mediated immune response, low levels of endogenous IL-10 have no appreciable effect; exogenous rhIL-10 has a limited effect on cytokine production and no effect on T lymphocyte proliferation or HLA expression.     

Tumor-specific Tc1, but not Tc2, cells deliver protective antitumor immunity.

We investigated whether secretion of multiple cytokines by CD8+ T cells is associated with improved protection against tumor challenge. We show that antitumor immunity induced by immunization with dendritic cells and a MHC class I-binding tumor peptide are dependent on secretion of IFN-gamma but not IL-4 or IL-5 by host cells. To further address the role of IL-4 and IL-5 in antitumor immunity, tumor-specific TCR-transgenic CD8+ T cells were activated in vitro to generate cytotoxic T (Tc) 1 cells that secrete high IFN-gamma and no IL-4 or IL-5 or Tc2 cells that secrete IL-4, IL-5, and some IFN-gamma. Both cell types killed target cells in vitro. Tc1 and Tc2 cells were adoptively transferred into syngeneic hosts, and their ability to protect against tumor challenge was compared. Tc1 cells were able to significantly delay tumor growth, whereas Tc2 cells or Tc2 cells from IFN-gamma(-/-) donors had no effect. This was due to neither the inability of Tc2 cells to survive in vivo or to migrate to the tumor site nor their inability to secrete IL-4 and/or IL-5 in the presence of limiting amounts of anti-CD3. However, IFN-gamma secretion by Tc2 cells was triggered inefficiently by restimulation with Ag compared with anti-CD3. We conclude that the ability to secrete "type 2" cytokines, and cytotoxic ability, have a limited role in antitumor immune responses mediated by CD8+ T cells, whereas the capacity to secrete high amounts of IFN-gamma remains the most critical antitumor effector mechanism in vivo.     

Experimental murine schistosomiasis in the absence of B7 costimulatory molecules: reversal of elicited T cell cytokine profile and partial inhibition of egg granuloma formation

The granulomatous inflammation in infection with the helminth Schistosoma mansoni represents a cellular hypersensitivity reaction mediated by, and dependent upon, MHC class II-restricted CD4+ Th cells sensitized to parasite egg Ags. The current work examines the role and significance of the B7:CD28/CTLA-4 pathway in providing the costimulation necessary for the activation of these pathogenic T cells. In vitro T cell responses in B7-1-/- mice, 7-8 wk postinfection, were no different from wild-type controls, but the absence of B7-2 molecules resulted in a decrease in egg Ag-induced proliferation with increased IFN-gamma production. Both B7-1-/- and B7-2-/- mice exhibited intact granuloma formation. In contrast, CD4+ Th cells from B7-1/2 double-deficient mice displayed a dramatic loss of proliferative capacity upon stimulation with egg Ag. Most strikingly, these T cells secreted only IFN-gamma, but not IL-4 and IL-10, a pattern entirely opposite to that displayed by wild-type controls. Despite these major differences in T cell reactivity, B7-1/2-/- mice had only a limited reduction of granuloma size and fibrosis, without appreciable difference in cellular composition. These results show that substantial granuloma formation can occur under conditions of limited T cell expansion and restricted Th1-type cytokine production. They also support the notion that the combined effect of B7 signaling is not as critical for Th1 cell activation as it is for the development of the Th2 dominant environment characteristic of the evolving schistosome infection in H-2b mice.     

TGF-beta and IL-10 regulation of IFN-gamma produced in Th2-type schistosome granulomas requires IL-12

Interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) regulate CD4+ T cell interferon-gamma (IFN-gamma) secretion in schistosome granulomas. The role of IL-12 was determined using C57BL/6 and CBA mice. C57BL/6 IL-4-/- granuloma cells were stimulated to produce IFN-gamma when cultured with IL-10 or TGF-beta neutralizing monoclonal antibody. In comparison, C57BL/6 wild-type (WT) control granuloma cells produced less IFN-gamma. IL-12, IL-18, and soluble egg antigen stimulated IFN-gamma release from C57BL/6 IL-4-/- and WT mice. IFN-gamma production in C57 IL-4-/- and WT granulomas was IL-12 dependent, because IL-12 blockade partly abrogated IFN-gamma secretion after stimulation. All granuloma cells released IL-12 (p70 and p40), and IL-12 production remained constant after anti-TGF-beta, anti-IL-10, recombinant IL-18, or antigen stimulation. C57 WT and IL-4-/- mouse granuloma cells expressed IL-12 receptor (IL-12R) beta1-subunit mRNA but little beta2 mRNA. TGF-beta or IL-10 blockade did not influence beta1 or beta2 mRNA expression. CBA mouse dispersed granuloma cells released no measurable IFN-gamma, produced IL-12 p70 and little p40, and expressed IL-12R beta2 and little beta1 mRNA. In T helper 2 (Th2) granulomas of C57BL/6 WT and IL-4-/- mice, cells produce IL-12 (for IFN-gamma production) and IL-10 and TGF-beta modulate IFN-gamma secretion via mechanisms independent of IL-12 and IL-12R mRNA regulation. We found substantial differences in control of granuloma IFN-gamma production and IL-12 circuitry in C57BL/6 and CBA mice.     

Epitopes of the Mycobacterium tuberculosis 65-kilodalton protein antigen as recognized by human T cells

A synthetic peptide approach has been used to identify the epitopes recognized by clonal and polyclonal human T cells reactive to the recombinant mycobacterial 65-kDa protein Ag. Three of the four epitopes identified were recognized as cross-reactive between Mycobacterium tuberculosis and Mycobacterium leprae, although their amino acid sequence in two of three cases was not identical. The peptide (231-245) defining an epitope recognized as specific to the M. tuberculosis complex contains two substitutions compared with the homologous M. leprae region of which one or both are critical to T cell recognition. The reactive T cell clones showed helper/inducer phenotype (CD4+, CD8-), and secrete IL-2, granulocyte-macrophage-CSF, and IFN-gamma upon Ag stimulation. The same clones display cytotoxicity against macrophages pulsed with the relevant peptides or mycobacteria.     

Activated T cells and monocytes have characteristic patterns of class II antigen expression

The expression of human histocompatibility class II Ag was measured on activated T cells and monocytes by quantitative mAb binding in direct two-color immunofluorescence. Monocytes activated by IFN-gamma bound an average of 2 x 10(6) DR-specific mAb, 3 x 10(5) DQ-specific mAb, and 7 x 10(5) DP-specific mAb per cell. For T cells activated by anti-CD3, a subpopulation bound 1 x 10(5) DR-specific mAb, 5 x 10(4) DQ-specific mAb and 5 x 10(4) DP-specific mAb per cell. These measurements were obtained after establishing a base line of class II Ag expression on resting B cells and monocytes. Resting B cells and those monocytes that were positive for class II Ag bound identical amounts of mAb; 3 x 10(4) DR-specific mAb, 3 x 10(3) DQ-specific mAb and 2 x 10(4) DP-specific mAb. However, most resting monocytes (75%) expressed only DR Ag. In the process of studying the expression of class II Ag on T cells, it was necessary to define and analyze the activated T cell state. Cell cultures activated with 0.3 ng/ml anti-CD3 had the highest expression of class II Ag on T cells, whereas those activated with 3.0 ng/ml anti-CD3 had the highest expression of IL-2R on T cells. Addition of IL-2 had no further effect on DR Ag expression on T cells but did up-regulate IL-2R expression. Reducing the initial monocyte concentration before activating T cells increased class II Ag expression on T cells without affecting IL-2R expression. The results obtained on T cell activation suggest that perhaps a lymphokine may be made by CD3-activated T cells which induces class II Ag expression on T cells.     

Mycobacterium tuberculosis induces differential cytokine production from dendritic cells and macrophages with divergent effects on naive T cell polarization

Th1-mediated cellular responses are important for protection in tuberculosis. However, the mechanisms and APC types responsible for initiating Th1 responses are not well understood. These studies show that macrophages and dendritic cells, albeit both being APC, respond differently following Mycobacterium tuberculosis infection and thereby have different consequences for the development of naive T cells. We report that M. tuberculosis-infected dendritic cells bias the polarization of OVA peptide-specific naive transgenic T cells to the Th1 phenotype, and, in contrast, in the presence of infected macrophages naive T cells do not develop a Th1 phenotype. Comparison of the cytokine profile expressed by the infected dendritic cells and macrophages revealed several differences, the most striking being that infected macrophages did not express the Th1-promoting cytokine IL-12. These studies also show that IL-10 is responsible for the failure of IL-12 production by M. tuberculosis-infected macrophages, and that the effects of IL-10 can be overcome by IFN-gamma priming. We speculate that the observed difference in response of the two APC types to M. tuberculosis infection may be a reflection of their respective roles in immune initiation and granuloma regulation.     

Properties of interleukin-1 and interferon-gamma receptors in B lymphoid cell line

We have previously shown that interleukin-1 alpha (IL-1 alpha) and interferon-gamma (IFN-gamma) induce surface IgM expression, stimulate Na+/H+ exchange, and activate protein kinase C in the murine pre-B lymphocyte cell line, 70Z/3. Because the two structurally different lymphokines induce similar effects, in this study we set out to compare the properties of the IL-1 and IFN-gamma surface receptors. In contrast to their similar cellular effects, we found that IL-1 alpha and IFN-gamma receptors have different properties. 70Z/3 have high (100 sites/cell) and low (900 sites/cell) affinity IL-1 receptors with dissociation constants (KD) 6 x 10(-11) and 10(-9) M, respectively. In contrast, IFN-gamma receptors are of one class with a KD of 3 x 10(-10) M and are at a higher number, 8000 sites/cell. After binding to their receptors both IL-1 alpha and IFN-gamma are internalized and intracellularly degraded, but the rate of internalization of IFN-gamma is greater than IL-1 alpha. The effective median concentrations (EC50) of IL-1 alpha- or IFN-gamma-induced surface IgM expression are similar (4-5 x 10(-12) M). However, at this concentration 10-fold more of IFN-gamma than IL-1 alpha molecules are bound per cell. Our studies indicate that structurally different lymphokines can induce similar biological events even though their signaling is mediated by surface receptors whose properties are different.     

Lethal granuloma disintegration in mycobacteria-infected TNFRp55-/- mice is dependent on T cells and IL-12

Genetically susceptible, TNFRp55 gene-deficient (TNFRp55-/-) mice succumb to infection with Mycobacterium avium. Before their death, M. avium-infected TNFRp55-/- mice develop granulomatous lesions that, in contrast to granulomas in wild-type syngeneic mice, undergo acute disintegration. To determine the factors involved in these events, we depleted T cell subsets or neutralized the inflammatory cytokines IFN-gamma, IL-12, or TNF in TNFRp55-/- mice infected i.v. with M. avium. Infected TNFRp55-/- mice treated with a control mAb became moribund between days 26 and 34 postinfection, showing widespread inflammatory cell apoptosis within disintegrating granulomas. In contrast, TNFRp55-/- mice depleted of either CD4+ or CD8+ cells after granuloma initiation stayed healthy until at least day 38 postinfection and showed no signs of granuloma destruction. Neutralization of IL-12, but not of IFN-gamma or TNF, also protected M. avium-infected TNFRp55-/- mice from granuloma decomposition and from premature death. Treatment with dexamethasone or with a specific inhibitor of inducible NO synthase did not prevent granuloma dissolution or death of TNFRp55-/- mice. In conclusion, granuloma disintegration in TNFRp55-/- mice is a lethal event that is dependent on IL-12 and that is mediated by an excess of T cells.     

Cachectin/tumor necrosis factor and interleukin-1 show different modes of combined effect on lipoprotein lipase activity and intracellular lipolysis in 3T3-L1 cells

Cachectin/tumor necrosis factor (cachectin/TNF) and interleukin-1 (IL-1) share many effects in various tissues and cells, including suppression of lipoprotein lipase (LPL) activity and enhancement of intracellular lipolysis. A possible interaction between cachectin/TNF and IL-1 in these lipase systems was studied in 3T3-L1 adipocytes. The two cytokines showed marked synergy in their suppression of LPL activity in these adipocytes. The least effective dose of cachectin/TNF or IL-1 was at around 5 x 10(-11) or 2.5 x 10(-12) M, respectively. However, when present in combination in amounts as small as 1/20 or 1/100 of the minimum effective dose for either cytokine alone (2.5 x 10(-12) M cachectin/TNF and 2.5 x 10(-14) M IL-1), the cytokines showed marked suppression of LPL activity. In marked contrast, such synergism was not seen for enhancement of intracellular lipolysis. This discrepancy in the combined effects of the two monokines on the two different enzyme systems in the same cells suggests that synergism between cachectin/TNF and IL-1 is unlikely at the level of their receptors on the surface of 3T3-L1 cells. Because the two monokines are considered to be secreted from macrophages under similar conditions, their effect on LPL suppression in many pathophysiological situations would be much greater than that of either monokine alone.     

IL-12 induction of mRNA encoding substance P in murine macrophages from the spleen and sites of inflammation

Substance P (SP), a neuropeptide, interacts with the neurokinin 1 receptor (NK-1R) on immune cells to help control IFN-gamma production. In murine schistosomiasis mansoni, schistosome worms produce ova that incite focal Th2-type granulomatous inflammation within the liver and intestines. Normal gut is characterized by a controlled state of inflammation. IL-10 knockout mice develop chronic Th1-type colitis spontaneously. Both schistosome granulomas and gut mucosa display an SP immune regulatory circuit. However, the origin and regulation of SP production at these sites of inflammation are poorly understood. Macrophages are a potential source of SP. We therefore studied macrophages (F4/80(+)) from these models of inflammation. SP mRNA (preprotachykinin A (PPT A)) was detected within the schistosome granuloma, spleen, and lamina propria macrophages. Compared with those from wild-type mice, granuloma macrophages from STAT6(-/-) mice had 10-fold higher PPT A mRNA expression, whereas in STAT4(-/-) animals, PPT A mRNA expression was nearly abolished. IL-12 signals via STAT4 to induce Th1-type inflammation. It was demonstrated that IL-12, but not IL-18, induces SP mRNA expression in resting splenic macrophages from Schistosoma-infected mice and in wild-type lamina propria mononuclear cells. Thus, macrophages are a source for SP at these sites of chronic inflammation, and IL-12 and STAT4 are regulators of macrophage SP mRNA expression.     

Type 1 and type 2 CD8+ effector T cell subpopulations promote long-term tumor immunity and protection to progressively growing tumor

Cytolytic CD8+ effector cells fall into two subpopulations based on cytokine secretion. Type 1 CD8+ T cells (Tc1) secrete IFN-gamma, whereas type 2 CD8+ T cells (Tc2) secrete IL-4, IL-5, and IL-10. Using an OVA-transfected B16 lung metastases model, we assessed the therapeutic effects of adoptively transferred OVA-specific Tc1 and Tc2 subpopulations in mice bearing established pulmonary malignancy. Effector cell-treated mice exhibiting high (5 x 105) tumor burdens experienced significant (p < 0.05) delays in mortality compared with those of untreated control mice, whereas high proportions (70-90%) of mice receiving therapy with low (1 x 105) tumor burdens survived indefinitely. Long-term tumor immunity was evident by resistance to lethal tumor rechallenge, heightened levels of systemic OVA Ag-specific CTL responses ex vivo, and detection of long-lived TCR transgene-positive donor cells accompanied by an elevation in the total numbers of CD8+ CD44high activated and/or memory T cells at sites of tumor growth. Long-lasting protection by Tc2 and Tc1 effector cells were dependent, in part, on both the level of tumor burden and effector cell-derived IL-4, IL-5, and IFN-gamma, respectively. We conclude that Tc1 and Tc2 effector cells provide immunity by different mechanisms that subsequently potentiate host-derived antitumor responses.     

Angiogenesis-inflammation cross-talk: vascular endothelial growth factor is secreted by activated T cells and induces Th1 polarization

Vascular endothelial growth factor (VEGF) and its receptors are critical in angiogenesis. The main player in the secretion and response to VEGF is the endothelial cell. We initiated this study to test whether T cells can secrete VEGF and are able to respond to it. Here we show that VEGF is secreted by T cells on stimulation by specific Ag or by IL-2 and by hypoxia; thus, activated T cells might enhance angiogenesis. Hypoxia also induced the expression in T cells of VEGFR2, suggesting that T cells might also respond to VEGF. Indeed, VEGF augmented IFN-gamma and inhibited IL-10 secretion by T cells responding to mitogen or Ag; thus, VEGF can enhance a Th1 phenotype. Encephalitogenic T cells stimulated in the presence of VEGF caused more severe and prolonged encephalomyelitis. Thus, T cells can play a role in angiogenesis by delivering VEGF to inflammatory sites, and VEGF can augment proinflammatory T cell differentiation.     

Simian immunodeficiency virus-induced changes in T cell cytokine responses in cynomolgus macaques with latent Mycobacterium tuberculosis infection are associated with timing of reactivation

Understanding the early immunologic events accompanying reactivated tuberculosis (TB) in HIV-infected individuals may yield insight into causes of reactivation and improve treatment modalities. We used the cynomolgus macaque (Macaca fascicularis) model of HIV-Mycobacterium tuberculosis coinfection to investigate the dynamics of multifunctional T cell responses and granuloma T cell phenotypes in reactivated TB. CD4(+) and CD8(+) T cells expressing Th1 cytokines (IFN-γ, IL-2, TNF) and Th2 cytokines (IL-4 and IL-10) were followed from latent M. tuberculosis infection to reactivation after coinfection with a pathogenic SIV. Coinfected animals experienced increased Th1 cytokine responses to M. tuberculosis Ags above the latent-response baseline 3-5 wk post-SIV infection that corresponded with peak plasma viremia. Th2 cytokine expression was not Ag specific, but strong, transient IL-4 expression was noted 4-7 wk post-SIV infection. Animals reactivating <17 wk post-SIV infection had significantly more multifunctional CD4(+) T cells 3-5 wk post-SIV infection and more Th2-polarized and fewer Th0-, Th1-polarized CD8(+) T cells during weeks 1-10 post-SIV infection than animals reactivating >26 wk post-SIV infection. Granuloma T cells included Th0-, Th1-, and Th2-polarized phenotypes but were particularly rich in cytolytic (CD107(+)) T cells. When combined with the changes in peripheral blood T cells, these factors indicate that events during acute HIV infection are likely to include distortions in proinflammatory and anti-inflammatory T cell responses within the granuloma that have significant effects on reactivation of latent TB. Moreover, it appears that mycobacteria-specific multifunctional T cells are better correlates of Ag load (i.e., disease status) than of protection.     

The substance P receptor is necessary for a normal granulomatous response in murine schistosomiasis mansoni

Immune cells within the granulomas of murine schistosomiasis mansoni make the neuropeptide substance P (SP) and express neurokine 1 receptor, which is the specific receptor for substance P (SPr). It was determined if mice with deletion of the SPr (SPr-/-) would develop a normal granulomatous response to schistosome ova during the course of natural infection. Mean liver granuloma size was smaller in SPr-/- mice compared with that of wild-type control animals. Although flow analysis revealed little difference in the cellular composition of the granulomas, both splenocytes and granuloma cells from SPr-/- mice produced much less IFN-gamma and IgG2a and less IgE. The expression of Th2 cytokines (IL-4/IL-5) and IgG1 was comparable to the wild-type control. The mouse with targeted disruption of its SPr had the nonmammalian gene encoding the enzyme beta-galactosidase inserted in exon 1 of the SPr gene. There was beta-galactosidase activity in many mononuclear cells scattered throughout the schistosome granulomas of SPr-/- mice. Also, a granuloma T cell line derived from this transgenic mouse produced beta-galactosidase. These results provide further evidence that in murine schistosomiasis SPr is displayed commonly on granuloma inflammatory cells and is important for granuloma development and expression of IFN-gamma circuitry in this natural infection.     

Glomerular mesangial cells in local inflammation. Induction of the expression of MHC class II antigens by IFN-gamma

Glomerular mesangial cells (MC) were isolated from rats and cultured for a prolonged period of time, resulting in a homogeneous cell population. MC were characterized as belonging to the smooth muscle type. They were negative for MHC class II expression. IFN-gamma and TNF alpha suppressed the proliferation of MC, demonstrating receptors for these cytokines on MC. IFN-gamma or TNF alpha, respectively, enhanced basal MHC class I Ag expression of proliferating cells in culture. The combination of the two cytokines yielded stronger effects. IL-1 beta was ineffective in enhancing MHC class I Ag expression, although MC possessed receptors for this cytokine. IFN-gamma dose dependently induced the expression of MHC class II Ag, while TNF alpha or IL-1 beta were ineffective alone. The combination of IFN-gamma with TNF alpha or IL-1 beta resulted in an enhanced induction of MHC class II Ag, compared to IFN-gamma administration alone. These findings suggest that proliferating mesangial cells of the smooth muscle type may participate in local inflammatory responses or substitute for macrophages by meeting the accessory cell requirement in the interaction with T lymphocytes. Furthermore, the data have important implications for the evaluation of the role of mesangial cells in autoimmune disease of the kidney.     

Relative contributions of NK and CD8 T cells to IFN-gamma mediated innate immune protection against Listeria monocytogenes

During the innate immune response to Listeria monocytogenes (LM), the secretion of IFN-gamma is crucial in controlling bacterial numbers. We have shown recently that CD8 T cells have the ability to rapidly secrete IFN-gamma independent of Ag, in response to IL-12 and IL-18, during a LM infection. In the current study, we compared the relative abilities of NK and CD8 T cells to provide innate immune protection. Upon transfer of either NK or memory OT-I T cells (specific for the OVA protein) into IFN-gamma-deficient hosts that were infected subsequently with wild-type LM, both cell types were found in the spleen and had the ability to secrete IFN-gamma. However, the OT-I T cells were more effective at providing innate immune protection as determined by spleen and liver LM burdens. We used immunocytochemistry to demonstrate that upon infection with LM, marginal zone macrophages were localized to the T cell area of the splenic follicle. Transferred memory OT-I T cells were also found in the T cell area of the spleen, co-localizing with the LM and macrophages. In sharp contrast, NK cells were found predominantly in the red pulp region of the spleen. In addition, memory OT-I T cells were also found to be associated with LM lesions in the liver. These results highlight the importance of CD8 T cells in innate immune responses to LM and suggest that their increased protective ability compared with NK cells is the result of their colocalization with LM and macrophages.