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Query: UMLS:C0021311 (Infection)
 38,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The modulation of expression of CD80 and CD86 on T cells following infection with human T lymphotropic virus (HTLV)-I/II and its functional importance in T-T cell interactions was examined. Infection with HTLV-I/II leads to constitutive expression of CD80 and CD86, concomitant to down-modulation of CD28 on T cells. The CD80/CD86+ HTLV-infected T cells stimulated proliferation of allogeneic and autologous resting T cells, which could be specifically blocked by a soluble CTLA-4Ig chimeric protein, anti-CD80 or anti-CD86, but not by anti-CD54. It was necessary to inhibit interaction with both ligands (CD80 and CD86) to optimally block HTLV-mediated proliferation of allogeneic and autologous resting T cells. Simultaneous addition of anti-CD8O and anti-CD86 Abs also inhibited production of IFN-gamma, TNF-alpha, and IL-4, with no effect on IL-10 production, for both allo- and autologous T cell proliferation. Further, there was a direct correlation between the spontaneous proliferation of lymphocytes from patients infected with HTLV-II and expression of CD80, which could be blocked by simultaneous addition of anti-CD80 and anti-CD86. Taken together, these results suggest that HTLV-infected CD80/CD86+ T cells serve as APCs, leading to a sustained proliferation of T cells, and that both ligands participate in allostimulation, autologous proliferation, as well as spontaneous proliferation of HTLV-II-infected PBMC.
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PMID:Costimulatory effects of T cell proliferation during infection with human T lymphotropic virus types I and II are mediated through CD80 and CD86 ligands. 875 37

Infection by human immunodeficiency virus (HIV)-1 is associated with quantitative and qualitative T cell alterations that severely impair the host's immune defense system. The molecular basis for this immunosuppression remains unclear. Peripheral blood mononuclear cells (PBMC) isolated from patients show markedly decreased interleukin (IL)-2 secretion but unaffected or even increased T helper (Th)2 cytokine production. T cell functional defects were recently reported to correlate more with T cell receptor (TcR) signaling, whereas signals provided by ligation of co-receptors CD27 and CD28 appeared to be preserved. Among the various mechanisms proposed to be involved in HIV-1-induced T cell dysfunction, we and others have reported that the nef gene product exhibited significant immunosuppressive activity. By using an inducible stably integrated nef gene, we demonstrated that Nef specifically down-regulated IL-2 and interferon (IFN)-gama produced upon TcR triggering. Here, using the same experimental system, we extended our initial observations to additional mitogenic signals, and investigated the co-stimulatory function of CD28. Nef down-regulated IL-2, but not IL-4 produced upon induction by combinations of mitogens that mimicked TcR signals together with CD28 mAb or CD28's natural ligand (CD80 and CD86). However, the co-signals provided by CD28 to up-regulate IL-2 induction were unaffected by Nef, since IL-2 produced by nef-transfected cells was proportionally enhanced to the same extent as that of control cells, either upon stimulation by the CD28 mAb or CD80 and CD86. In addition, phosphatidylinositol-3 kinase recruitment induced upon CD28 triggering was also found to be unaltered by nef expression. Together with the observation that similar levels of the Nef protein were detected in nef-transfected cells and upon infection of PBMC, these data suggest a selective immunosuppression induced by nef in human T cells by altering TcR signaling without detectable impact on CD28 co-receptor function. These data agree with the T cell defects observed in PBMC isolated from HIV-infected individuals.
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PMID:Evidence for intact CD28 signaling in T cell hyporesponsiveness induced by the HIV-1 nef gene. 876 22

Although inbred strains of mice are classified as genetically resistant or susceptible to Leishmania major based upon their ability to control infection, other factors such as the strain, dose, and site of parasite inoculation can also affect the outcome of the disease. Here we used the F1 progeny of BALB/c (susceptible) and C57BL/6 (resistant) mice (designated CB6F1) to investigate whether mice or intermediate susceptibility to infection differed from the parental strains in their ability to control infections at different cutaneous sites. CB6F1 mice developed progressive disease when inoculated in the dorsal skin, but healed infections in the footpad. Consistent with these observations, mice inoculated in the footpad ultimately developed Th1 responses, known to be required for healing, while Th2 responses developed in mice inoculated in the dorsal skin. However, IL-4 and IFN-gamma production during the first few weeks of infection was similar in CB6F1 mice inoculated at either site, suggesting that factors in addition to the relative levels of these cytokines produced early in infection may influence the nature of the antileishmanial immune response, and the eventual disease outcome. Infection in CB6F1 mice provides a model for the study of immunity to L. major in genetically identical animals, in which a prolonged mixed Th1/Th2 cytokine pattern initially develops, but ultimately diverges into more defined Th1 and Th2 type responses.
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PMID:The influence of the site of parasite inoculation on the development of Th1 and Th2 type immune responses in (BALB/c x C57BL/6) F1 mice infected with Leishmania major. 881 3

Helper T (Th) cells can be classified functionally into two main types. Broadly, Th1 cells play a major role in eliminating viral pathogens, while Th2 cells mediate anti-parasite immunity and allergic responses. These functions are thought to depend on characteristic and distinct patterns of cytokine production. Infection with human respiratory syncytial virus, an important common cold virus, causes transient lymphocytic bronchiolitis in mice. Activated T cells are partly responsible for this disease, but also eliminate the virus. To show whether polarized cytokine production occurs in individual cells during viral bronchiolitis, we sampled murine bronchoalveolar lavage and mediastinal lymph node cells before and after infection. RT-PCR of cellular mRNA and flow cytometric analysis of intracellular cytokine production showed a rapid IFN-gamma response at both sites, which persisted for more than 3 weeks in the lung. Most IFN-gamma-producing cells were CD8+. Some early CD4+ IFN-gamma-producing cells also made IL-10. Only low levels of IL-2, IL-4 and IL-5 mRNA or protein expression were detected at any time at either site. No cytokines were detected in B cell populations at either site. These novel techniques show the true complexity of cytokine production patterns on a cell-by-cell basis, allowing T cells to be reclassified according to function.
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PMID:Th1 and Th2 cytokine induction in pulmonary T cells during infection with respiratory syncytial virus. 888 77

Infection with the nematode, Nippostrongylus brasiliensis, results in a Th2-dominated immune response. We describe the dynamics of this response in both local and systemic environments. Th2-type responses were evident first in the mesenteric lymph node, with parasite antigen-specific proliferation and IL-4/IL-5 release peaking at Days 7-9 postinfection, shortly before expulsion of the adult worms from the gut. IFN-gamma responses were not observed in the mesenteric lymph node. Responses in the spleen generally followed those in the mesenteric lymph nodes by 2-3 days and showed a greater degree of Th1-type cytokine production. N. brasiliensis was shown to be a powerful inducer of IL-4 responses with as few as six infective N. brasiliensis larvae eliciting IL-4 production in the mesenteric lymph node, but only high doses of larvae (600) elicited IL-4 secretion in the spleen. Similar levels of IL-4 production by lymph node cells stimulated with Con A or parasite antigen postinfection indicated the extent of polyclonal Th2 stimulation by this parasite. Infection of IL-4-deficient mice showed that despite the absence of IL-4-dependent Th2 responses, these mice were able to curtail egg production and expel adult N. brasiliensis in a time frame similar to that of fully immunocompetent animals. These results emphasize the magnitude of the Th2 response to N. brasiliensis and also show that IL-4 is not a prerequisite for the development of immunity to N. brasiliensis.
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PMID:Nippostrongylus brasiliensis: cytokine responses and nematode expulsion in normal and IL-4-deficient mice. 888 33

Immunoglobulin (Ig) class switching in B cells is regulated by stimuli transduced by cytokines and cell-cell contact. Among these stimuli, interleukin (IL)-4 has been considered an absolute prerequisite for class switching to IgE in the mouse. Here we report that IL-4-deficient (IL-4-/-) and wildtype mice had comparably elevated serum IgE levels during the course of a murine retrovirus-induced immunodeficiency syndrome, MAIDS. IgE switching in IL-4-/- mice was also induced by injection of anti-IgD antibody. Treatment with anti-IgD induced germline epsilon (g epsilon) transcripts with comparable efficiency in IL-4-/- mice and controls, but the levels of productive epsilon transcripts (p epsilon) were lower by a factor of 200 and serum IgE levels were lower by a factor of 300 in IL-4-/- mice as compared with controls. Induction of g epsilon after anti-IgD treatment of IL-4-/- mice was unaffected by simultaneous treatment with monoclonal antibodies to IL-4 and IL-4 receptor alpha chain. Infection of IL-4-/- mice with Nippostrongylus brasiliensis, a potent stimulus for IgE production, resulted in induction of g epsilon transcripts; however, p epsilon transcripts were barely detectable and serum IgE was not detected. These findings establish a novel IL-4-independent pathway for IgE switching in the mouse that is strongly activated in retroviral infection but weakly in nematode infection. This pathway appears to be dependent on distinct factors that separately control induction of g epsilon transcription and switch recombination to p epsilon.
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PMID:Interleukin (IL)-4-independent immunoglobulin class switch to immunoglobulin (Ig)E in the mouse. 892 Aug 55

Competitive PCR was used to evaluate the expression of cytokine, granzyme B, and chemokine genes in lymph nodes of macaques recently infected with the simian immunodeficiency virus (SIV) pathogenic molecular clone SIVmac239 (n = 16), the nonpathogenic vaccine strain SIVmac239 delta nef (n = 8), and the nonpathogenic molecular clone SIVmac1A11 (n = 8). For both SIVmac239 and its nef-deleted derivative, strong expression was observed as early as 7 days postinfection for interleukin 1beta (IL-1beta), IL-6, tumor necrosis factor alpha, gamma interferon, and IL-13. The levels of gene induction were equally intense for both viruses despite a lower viral load for SIVmac239 deltanef compared with that for SIVmac239. However, the nature of the cytokine network activation varied with the viral inocula. Primary infection with SIVmac239 was characterized by a higher level of IL-4, IL-10, MIP-1alpha, MIP-1beta, MCP-1, and RANTES gene expression and a lower level of IL-12 and granzyme B gene expression compared with infection with SIVmac239 delta nef. Thus, infection with nef-deleted SIV was associated with a preferential Th1 versus Th2 pattern of cytokine production. Infection with SIVmac1A11 was characterized by a delayed immune response for all markers tested. The unique patterns of cytokine and chemokine gene expression in lymph nodes correlated nicely with the pathogenic potential of the SIV strains used as well as with differences in their ability to serve as protective vaccines.
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PMID:Early cytokine and chemokine gene expression in lymph nodes of macaques infected with simian immunodeficiency virus is predictive of disease outcome and vaccine efficacy. 899 46

The evidence that T lymphocytes play a key role in the pathogenesis of psoriasis is now compelling. Eruption of psoriatic skin lesions coincides with epidermal infiltration and activation of T cells, and spontaneous or treatment-induced resolution of the lesions is preceded by the reduction or disappearance of epidermal T cells. An upregulation has also been demonstrated for various molecules associated with T-cell mediated inflammation, and treatments selectively directed against T cells have proved very effective. Infections with group A beta-haemolytic streptococci have been associated with onset of acute psoriasis and exacerbation of chronic psoriasis. Such infections are also frequently accompanied by erythematous skin rashes. Also, recent reports indicate that streptococcal superantigens can induce expression of cutaneous lymphocyte antigens (CLA), believed to play a major role in enabling T cells to migrate to the skin. Furthermore, T-cell lines isolated from psoriatic lesions may show strong reactivity to streptococcal antigens. We have postulated that psoriasis is an autoimmune disease mediated by T cells reacting to epitopes that are common to streptococcal M-proteins and keratins. To investigate this possibility, circulating T cells from 12 patients with active psoriasis, paired controls, and six patients with atopic dermatitis were challenged in vitro with five synthetic 20aa (amino acid) M-peptides: production of IFN-gamma and IL-4 was analysed by ELISPOT and RT-PCR techniques. Four of these peptides shared five to six aa sequences with several type I keratins and one did not. In 10 of the 12 psoriasis patients, measurable IFN-gamma production could be induced by one or more of the four peptides that share sequences with keratins. A borderline response was observed in only four of the 18 controls: the dermatitis patients were all negative. The only peptide that shared 6aa with keratins was the one that induced a response in the psoriatic patients most frequently, and four of them showed the strongest response to this peptide while none of the controls reacted to it. In all instances negligible responses were observed to the control peptide that did not share sequences with keratins. Except for PHA-stimulated controls, IL-4 responses could not be detected by either ELISPOT or RT-PCR and there was generally good agreement between the two techniques. A marked reduction in the M-peptide-induced IFN-gamma responses was observed in the psoriasis patients during remission induced by UVB treatment, while their responses to streptokinase-streptodornase were not affected. Thus, active psoriasis is associated with a Th1 type response to short peptides with epitopes shared by streptococcal M-protein and keratin. This is consistent with the hypothesis that psoriasis may be induced and exacerbated in susceptible individuals by M-protein-specific Th1-like cells that cross-react with human epidermal keratin.
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PMID:Is psoriasis induced by streptococcal superantigens and maintained by M-protein-specific T cells that cross-react with keratin? 902 Sep 31

Infection of C57BL/6 mice with a mixture of murine leukemia viruses (MuLVs) designated LP-BM5 MuLV leads to a disease characterized by progressive immunodeficiency and lymphoproliferation, known as murine AIDS (MAIDS). The development of MAIDS is associated with increased B-cell lymphoblast proliferation, but there is reason to believe that T-cell function and, particularly, T-cell-derived cytokines may also play a role. We have previously shown that concurrent infection with Leishmania major (which induces a strongly polarized Th1 response in C57BL/6 mice) and LP-BM5 MuLV modulates the disease induced by both infections. Here we show by treatment of mice with anticytokine antibodies that this modulation is largely exerted through the balance of Th1 and Th2 cytokines. Infected mice treated with antibodies to interleukin-4 and interleukin-10 exhibited a delayed development of MAIDS-related pathology and maintained T-cell responsiveness longer than mice treated with control antibody. Gamma interferon induced by coinfection with L. major synergized with anti-IL-4 treatment to inhibit the development of MAIDS pathology. Conversely, treatment with anti-gamma interferon led to a significant increase in splenomegaly and lymphadenopathy and slightly exacerbated loss of T-cell function. These data suggest that the production of Th2-associated cytokines may promote MAIDS pathology, while Th1-associated cytokines may help control the disease.
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PMID:Modulation of murine AIDS-related pathology by concurrent antibody treatment and coinfection with Leishmania major. 909 44

Altered cytokine transcription might play an important role in the pathogenesis of human immunodeficiency virus (HIV) infection in humans. The infection of rhesus macaques with simian immunodeficiency virus (SIV) provides a relevant animal model for HIV infection. Therefore, we evaluated the cyokine transcription of phytohemagglutinin (PHA)-stimulated lymphocytes in the early phase after infection of four rhesus macaques with pathogenic SIV-mac239. To determine transcription of interleukin (IL)-2, interferon (IFN)-gamma, IL-4, IL-6, and IL-10 we established a semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). After inoculation with SIV, all monkeys became productively infected and developed an acquired immunodeficiency syndrome (AIDS) like disease. Infection was associated with a proliferation dysfunction of monkey lymphocytes in response to PHA. In addition, a decreasing overall cytokine transcription could be observed during the course of SIV infection. These findings demonstrate that an impairment of the lymphocyte function is associated with a reduced cytokine transcription in the early phase of an immunodeficiency virus infection. The observed differences of cytokine expression might contribute to the impaired immune response of SIV-infected monkeys and HIV-infected humans.
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PMID:Impaired mitogen-driven proliferation and cytokine transcription of lymphocytes from macaques early after simian immunodeficiency virus (SIV) infection. 921 Feb 80


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