Specific activated T cells regulate IL-12 production by human monocytes stimulated with Cryptococcus neoformans

IL-12 production mediated by a T cell-independent and/or T cell-dependent pathway was investigated in human monocytes responding to Cryptococcus neoformans. The data of this study showed that: 1) appreciable levels of IL-12 were observed when freshly isolated monocytes were exposed to acapsular C. neoformans or Candida albicans and secretion occurred within 24-48 h of incubation; 2) monocytes alone were poor producers of IL-12 when stimulated with encapsulated C. neoformans; 3) the presence of specific anti-glucuronoxylomannan mAb favored IL-12 secretion and Fc cross-linking could play a role; 4) monocytes were able to secrete consistent levels of IL-12 when cultured with activated T cells responding to C. neoformans; 5) the maximum secretion of IL-12 was observed at 5-7 days of culture and was strongly regulated by the presence of endogenous IFN-gamma; and 6) the interaction between CD40 on monocytes and CD40 ligand on activated T lymphocytes responding to C. neoformans played a critical role in IL-12 secretion. These data highlight the mechanisms of IL-12 production by human monocytes exposed to C. neoformans, indicating a possible biphasic secretion of IL-12, dependent on the direct effect of fungal insult, and characterized by consistent secretion of IL-12 that is dependent on the interaction of CD40 with the CD40 ligand expressed on activated T cells responding to C. neoformans.     

Beta-galactoside-binding protein secreted by activated T cells inhibits antigen-induced proliferation of T cells

We have used mRNA differential display PCR to search for genes induced in activated T cells and have found the LGALS1 (lectin, galactoside-binding, soluble) gene to be strongly up-regulated in effector T cells. The protein coded by the LGALS1 gene is a beta-galactoside-binding protein (betaGBP), which is released by cells as a monomeric negative growth factor but which can also associate into homodimers (galectin-1) with lectin properties. Northern blot analysis revealed that ex vivo isolated CD8+ effector T cells induced by a viral infection expressed high amounts of LGALS1 mRNA, whereas LGALS1 expression was almost absent in resting CD8+ T cells. LGALS1 expression could be induced in CD4+ and CD8+ T cells upon activation with the cognate peptide antigen and high levels of LGALS1 expression were found in concanavalin A-activated T cells but not in lipopolysaccharide-activated B cells. Gel filtration and Western blot analysis revealed that only monomeric betaGBP was released by activated CD8+ T cells and in vitro experiments further showed that recombinant betaGBP was able to inhibit antigen-induced proliferation of naive and antigen-experienced CD8+ T cells. Thus, these data indicate a role of betaGBP as an autocrine negative growth factor for CD8+ T cells.     

Early-onset and adult periodontitis associated with abnormal cytokine production by activated T lymphocytes

There is growing evidence for an important role of the immune system in the pathogenesis of periodontitis. To further characterize the possible immunoregulatory dysfunction of peripheral blood mononuclear cells (PBMC) in periodontitis patients, we investigated functional aspects of PBMC from patients with early-onset periodontitis (EOP) and adult periodontitis (AP). Compared to controls, we observed decreased proliferative responses of PBMC from patients with EOP following stimulation with a mitogenic stimulus (phytohemagglutinin). To investigate whether this abnormality reflects a modulation in cytokine production, we measured the in vitro production of interleukin (IL)-3, IL-5, granulocyte macrophage colony-stimulating factor (GM-CSF), and interferon-gamma (IFN-gamma) by activated PBMC. PBMC in EOP patients expressed significantly decreased levels of IFN-gamma protein in response to mitogenic stimulation. Reduced IFN-gamma secretion was associated with decreased IFN-gamma and IL-2 mRNA expression in these cells, as well as decreased HLA-DR surface expression on monocytes. On the other hand, we observed significantly higher levels of IL-5 and GM-CSF in the same system using PBMC from AP patients. These were comparable to the levels observed for patients with allergic asthma. These data imply that EOP is associated with decreased Th1-like cytokine expression, and that the PBMC response from patients with AP is predominantly Th2/Th0 in nature.     

CD4-mediated inhibiton of IL-2 production in activated T cells

The role of CD4 in T cell activation has been attributed to its capacity to increase the avidity of interaction with APC and to shuttle associated Lck to the TCR/CD3 activation complex. The results presented in this study demonstrate that ligation of CD4 inhibits ongoing responses of preactivated T cells. Specifically, delayed addition of CD4-specific mAb is shown to inhibit Ag- or mAb-induced responses of both primary T cells and T cell clonal variants. The Ag responses of the latter are independent of the adhesion provided by CD4; thus the observed inhibition is not due to blocking CD4-MHC interactions. Further, analysis of the clonal variants demonstrates that CD4-associated Lck is not essential for the inhibition observed, as anti-CD4 inhibits responses of clonal variants, expressing a form of CD4 unable to associate with Lck (double cysteine-mutated CD4). The inhibition is counteracted by the addition of exogenous IL-2, demonstrating that the block is not due to a lesion in IL-2 utilization, rather its production. It is demonstrated that the delayed addition of anti-CD4 results in a rapid reduction in steady-state levels of IL-2 mRNA in both primary T cells and clonal variants.     

Perforin and Fas killing by CD8+ T cells limits their cytokine synthesis and proliferation

During an immune response, effector CD8+ T cells can kill infected cells by the perforin-dependent pathway. In comparison to CD4+ T cells, which are major sources of cytokines, normal CD8+ T cells produced less interleukin 2 and interferon gamma, and proliferated less vigorously after antigenic stimulation. Killing of target cells was a major cause of these reduced responses, since perforin-deficient CD8+ T cells showed substantially increased cytokine synthesis and proliferation. Cytotoxicity by the alternate Fas pathway also resulted in self-limitation of CD8+ T cell cytokine synthesis. This relationship between cytotoxicity and cytokine synthesis may regulate CD8+ T function in different phases of an immune response.     

Analysis of the in vitro cytokine production by liver-infiltrating T cells of patients with autoimmune hepatitis

The pathogenic mechanisms underlying the development of autoimmune hepatitis (AIH) are still unclear. Since AIH is associated with the presence of various autoantibodies and certain HLA subtypes, it is likely that T and B cells play a major role in this disease. In this study we have determined the functional capacities of in vivo preactivated liver-infiltrating T cells (LTC) from patients with AIH. As controls we used LTC from patients with non-autoimmune hepatitis (non-AIH). Our results show that preactivated LTC from patients with AIH predominantly (190/255 clones) reside in the CD4+ population, whereas LTC in non-AIH are dominated by the CD8+ phenotype (148/254 clones). In view of this finding we have investigated the cytokine secretion patterns of 102 randomly chosen CD4+ T cell clones from six patients with AIH. As controls we have used 58 CD4+ LTC from 11 patients with non-AIH. All clones were stimulated by lectin and irradiated accessory cells and subsequent cytokine production was evaluated. LTC from patients with AIH have a lower interferon-gamma (IFN-gamma)/IL-4 ratio compared with LTC from non-AIH. Although clones from some patients with AIH produced very high amounts of IL-4 in vitro, this was not a constant finding. These results show that in vivo preactivated LTC from patients with AIH are mostly CD4+ T cells that produce more IL-4 than IFN-gamma. In contrast, LTC from patients with non-AIH are dominated by CD8+ and CD4+ T cells that produce significantly less IL-4 than IFN-gamma. Thus, liver-infiltrating T cells from patients with AIH and non-AIH belong to different functional T cell subsets. This may have implications for the regulation of humoral and cellular immune responses in inflammatory liver disease.     

Distinct kinetics of cytokine production and cytolysis in effector and memory T cells after viral infection

NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) is the key catabolic enzyme controlling levels of biologically active PGs. PGDH is localized to syncytiotrophoblast in placenta, and to trophoblast cells in chorion. To examine the regulation of PGDH by steroids and to determine any changes with labor, we obtained placenta and chorion from term elective cesarean section or spontaneous delivery and isolated trophoblast cells using a Percoll density gradient. Cells were treated with varying concentrations of cortisol, progesterone, the synthetic progestins R5020, and medroxyprogesterone acetate with or without RU486 or the specific progesterone receptor antagonist, onapristone, and the 3beta-hydroxysteroid dehydrogenase inhibitor, trilostane. The activity of PGDH was assessed by measurement of 13,14-dihydro-15-keto-PGF2alpha. PGDH messenger ribonucleic acid was quantified by in situ hybridization and computerized image analysis. The basal output of 13,14-dihydro-15-keto-PGF2alpha was lower in placenta or chorion collected at spontaneous labor than in that obtained at elective cesarean section. Cortisol had a significant dose-dependent inhibitory effect on PGDH activity in both placental and chorion trophoblast cells and significantly decreased levels of PGDH messenger ribonucleic acid. Responses were similar between tissues from laboring and nonlaboring women. PGDH activity was increased by R5020 and medroxyprogesterone acetate and was inhibited by RU486, onapristone, and trilostane. We conclude that cortisol inhibits PGDH activity and expression and that progestagens increase PGDH activity in human chorion and placenta.     

Urocanic acid enhances IL-10 production in activated CD4+ T cells

The immunosuppressive effects of UV radiation have been well documented. This suppression has been attributed to the action of the cis form of urocanic acid (UCA), a photoproduct of trans-UCA, a natural constituent of the skin. Here, we show that mouse spleen cells preincubated with cis-UCA have a diminished proliferative response to allogeneic cells in MLC and to stimulation with anti-CD3 mAb. Cells preincubated with cis-UCA also had a decreased ability to serve as APC and to stimulate the proliferation of allogeneic lymphocytes in MLC. Simultaneously, the production of IL-2 and IFN-gamma by cells preincubated with cis-UCA was decreased. However, IL-10 gene expression and IL-10 protein secretion by spleen cells stimulated in the presence of cis-UCA were significantly enhanced. The principal cell population displaying the cis-UCA-induced elevated production of IL-10 was CD4+ T cells, which were shown to be a direct target of cis-UCA action. This was also supported by the observation that production of IL-10 by stimulated splenic non-T cells or by macrophages was not altered by cis-UCA. The enhanced production of IL-10 by activated CD4+ T cells may represent a novel pathway of UVB radiation-induced, cis-UCA-mediated immunosuppression. We suggest that the elevated production of IL-10 by activated CD4+ T cells may account for the suppressor T cell phenomena described in UV-irradiated recipients.     

Increased production of a Th2 cytokine profile by activated whole blood cells from rheumatoid arthritis patients

The results of primary trabeculectomy with and without mitomycin C (MMC) were evaluated in young glaucoma patients. The patients, 15-40 years of age, were divided into two main groups and two subgroups. In group IA, primary Cairns type trabeculectomy was performed in 24 eyes of 24 patients with juvenile glaucoma; in group IB, trabeculectomy + MMC 0.4 mg/ml in 3 min was done in 20 eyes of 20 patients with juvenile glaucoma; in group IIA, primary trabeculectomy was performed in 20 eyes of 20 patients with developmental glaucoma, and in group IIB, trabeculectomy + MMC 0.4 mg/ml in 3 min was performed in 16 eyes of 16 patients with developmental glaucoma. The success rate of the surgery was 75% in group IA, 90% in group IB, 50% in group IIA, and 75% in group IIB. There was no statistically significant difference among the groups in terms of success rates of trabeculectomies (p > 0.05).     

Analysis of cytokine production by Mycobacterium-reactive T cells. Failure to explain Mycobacterium leprae-specific nonresponsiveness of peripheral blood T cells from lepromatous leprosy patients

Recent analyses of antimycobacterial T cells clones from a small number of individuals indicate that mycobacteria preferentially induce Th cells that produce high levels of IFN-gamma and no or little IL-4 in Mycobacterium leprae-resistant tuberculoid leprosy (TT) patients and healthy subjects, whereas in one study M. leprae-induced Ts clones from polar lepromatous leprosy (LL) patients showed a reciprocal cytokine secretion profile and mediated their suppressive activity via the release of high levels of IL-4. We have evaluated these findings in peripheral blood T cells from a larger panel of TT and LL patients as well as healthy individuals. Mycobacterium-reactive T cell lines generated from the PBMC of these individuals were tested for cytokine secretion and proliferative capacity in response to M. leprae, Mycobacterium tuberculosis, and various individual mycobacterial Ag. The lepromatous pole of the leprosy spectrum was additionally investigated by analyzing the cytokine-secretion profile of M. leprae-induced (suppressor) T cell clones as well as primary ex vivo PBMC. All T cell lines from healthy individuals and TT patients responding to M. leprae, M. tuberculosis, or individual Ag, produced high levels of IFN-gamma and TNF-alpha but little or no IL-4 and IL-6. At the lepromatous pole, T cell lines failed to proliferate upon stimulation with M. leprae but in some cases produced significant levels of IFN-gamma. No IL-4 or IL-6 secretion was observed in response to M. leprae. These lines displayed strong proliferation and Th1-like cytokine production upon stimulation with M. tuberculosis. Similarly, stimulation of primary PBMC from LL patients with M. leprae or M. tuberculosis resulted in the release of IFN-gamma but no detectable IL-4 production. Control tetanus toxoid-reactive T cell lines from the same individuals instead produced large amounts of IL-4 and low levels of IFN-gamma. The analysis of M. leprae-induced T cell clones, including those with known suppressive activity, revealed that all lepromatous T cell clones produced large amounts of IFN-gamma. Most of these clones released no or little IL-4, but some clones produced higher levels of IL-4 in addition to IFN-gamma. Most clones tested produced IL-10 as well. The suppressor activity of suppressor T cell clones could not be inhibited by a neutralizing anti-IL-4 antibody and only in one case by neutralizing anti-IL-10 antibody. Anti-IL-4 and anti-IL-10 could not overcome the M. leprae-specific unresponsiveness observed in primary PBMC from LL patients.(ABSTRACT TRUNCATED AT 400 WORDS)     

Activation of T cells by superantigen: cytokine production but not apoptosis depends on MEK-1 activity

Engagement of the TCR may result in proliferation and cytokine release or programmed cell death. These two outcomes may be the consequence of distinct T cell receptor-coupled signal transduction pathways or may reflect quantitative differences in signaling strength via a single pathway. Here we show that genetic inhibition of MAP kinase kinase (MEK) by a dominant negative mutant or through chemical inhibition by PD98059 inhibits IL-2 secretion but not programmed cell death after TCR ligation by superantigen. This supports the hypothesis that T cell cytokine release and apoptosis result from signaling through distinct pathways and implies that the molecular signaling mechanisms regulating apoptosis of mature T cells and negative selection of thymocytes may be similar.     

Human endothelial cells effectively costimulate cytokine production by, but not differentiation of, naive CD4+ T cells

We compared costimulatory signals provided by human endothelial cells (ECs) to those provided by conventional bone marrow-derived APCs, i.e., peripheral blood-adherent mononuclear cells (PBAMCs), by measuring their effects on cytokine production by naive or memory CD4+ T cells stimulated by PHA. In these assays, ECs effectively costimulate secretion of IL-2, IFN-gamma, and IL-4 from both naive and memory CD4+ T cells, quantified by ELISA or intracellular cytokine staining. ECs, which lack B7 molecules, use predominantly leukocyte-function associated Ag 3 (LFA-3) to provide costimulation. ECs are comparable to or better than PBAMCs, which use both the LFA-3 and B7 molecules, at costimulating IL-2 and IL-4 production. ECs are less effective than PBAMCs at costimulating IFN-gamma production by naive T cells. ECs do not secrete IL-12, and addition of exogenous IL-12 enables ECs to costimulate IFN-gamma at a level comparable to that observed with PBAMCs. ECs do not promote differentiation of naive T cells to Th1-like cells, whereas PBAMCs do. Again, addition of exogenous IL-12 enables ECs to do so. Transfection of ECs to express B7-1 or B7-2 is less effective than IL-12 supplementation for restoring these responses. These experiments suggest that a deficiency in costimulation due to lack of B7 molecule expression does not fully explain the inability of ECs to activate resting naive CD4+ T cells.     

Seed extract of Aeginetia indica L induces cytokine production and lymphocyte proliferation in vitro

The development of the human medial superior olivary nucleus was studied in serial sections of 10 fetuses at 12-35 weeks of gestation (WG), an infant at 2 months of age and an adult of 63 years using an electronic planimeter with a computer. Morphometric analysis suggested that the development of the human medial superior olivary nucleus accelerates between 16 and 21 WG in terms of columnar lengths and volumes, neuronal sizes and circularity ratios, while it matures gradually in terms of the amount of Nissl bodies.     

Activated T helper 1 and T helper 2 cells differentially express the beta-2-adrenergic receptor: a mechanism for selective modulation of T helper 1 cell cytokine production

We recently reported that resting clones of murine Th1 cells, but not resting Th2 cells, expressed a detectable level of the beta-2-adrenergic receptor (beta 2AR). In the present study, we proposed that the level of beta 2AR expression on anti-CD3 mAb-activated CD4+ effector Th cells may differ from the level on resting cells, and that a change in receptor expression may alter the functional responsiveness of these cells to either the beta 2AR-selective ligand terbutaline or the sympathetic neurotransmitter norepinephrine. Following anti-CD3 activation, the beta 2AR was expressed on Th1 cells, but not Th2 cells. The number of binding sites on Th1 cells was maintained, with no change in affinity, over a 24-h activation period. When Th clones were exposed to terbutaline following anti-CD3 activation, Th1 cell, but not Th2 cell, cytokine production was modulated. IL-2 production by Th1 cells was decreased, while IFN-gamma production was not significantly altered. The decrease in IL-2 production was concentration dependent and was blocked by an antagonist. In comparison with control supernatants, the lower level of IL-2 present in terbutaline-exposed culture supernatants supported the proliferation of an IL-2-dependent Th1 clone to a lesser degree. Additionally, norepinephrine down-modulates IL-2, but not IFN-gamma, production by binding specifically to the beta-adrenergic receptor. Thus, a detectable level of the beta 2AR is expressed on activated Th1 cells, but not activated Th2 cells, thereby providing a mechanism by which IL-2 production is preferentially modulated by an endogenous and therapeutic ligand following Th1 cell activation.     

Type D SRV-2 virus-specific CD8+ and CD4- CD8- T cells that regulate virus-induced T cell proliferation in Celebes macaques

These studies defined SRV-2 envelope peptides 96-102, 127-152, and 233-249 as T cell epitopes that induce significant T cell proliferation. Peripheral blood lymphocytes of Celebes macaques (Macaca nigra) exposed to SRV-2 and currently virus- antibody+, cultured with SRV-2 virus show strongly suppressed T cell responses and have two immunoregulatory T cell populations.     

Oral administration of the bacterial superantigen staphylococcal enterotoxin B induces activation and cytokine production by T cells in murine gut-associated lymphoid tissue

The toxicity of the staphylococcal enterotoxins (SEs) has been linked to the activation of large numbers of T cells in the peripheral lymphoid tissues. Because the primary manifestations of foodborne enterotoxic poisoning are associated with the gastrointestinal tract, we have compared the responses of T cells in the gut-associated lymphoid tissue and in the periphery to intragastric (i.g.) and i.p. administration of SEB. Intraperitoneal SEB results in an early expansion of peripheral Vbeta8+ T cells and Th1 cytokine secretion followed by deletion at 7-10 days. We found that i.g. SEB rapidly (within 4 h) leads to the expansion and activation of Vbeta8+ T cells in the Peyer's patch and mesenteric lymph nodes. Analysis of cytokine mRNA in purified Vbeta8+ T cells by competitive RT-PCR showed that, 4 h after i.g. SEB, the induction of mRNA for IL-2 and IFN-gamma is about 10-fold greater in mucosal than in peripheral lymphoid tissue. Our results show that activated mucosal T cells expand and up-regulate cytokine mRNA in response to luminal exposure to SEB, suggesting a role for the gut-associated lymphoid tissue in the gastrointestinal manifestations of enterotoxic poisoning.     

Antigen-specific T lymphocytes regulate lipopolysaccharide-induced apoptosis of dendritic cells in vivo

The potent accessory properties of dendritic cells (DC) develop sequentially during a process termed "maturation." Splenic DC undergo functional maturation in vivo in response to the bacterial product LPS and migrate from the marginal zone to the T cell areas. The redistribution of fully mature DC, which present Ags encountered in the periphery, in the T cell area is likely to result in T cell priming. Unexpectedly, we found that DC rapidly die by apoptosis once they have entered the T cell zone. Injection of OVA peptide in OVA-specific, TCR-transgenic mice strongly delays the LPS-induced apoptosis of DC in situ. We conclude that mature DC are programmed to die unless they receive a survival signal from T cells and that the regulation of DC survival may be a mechanism aimed at controlling the initiation and the termination of the immune response.