Interleukin (IL)-4 production by human T cells: differential regulation of IL-4 vs. IL-2 production

Anti-inflammatory effects of the phosphodiesterase type 4 inhibitor CHF6001 on bronchoalveolar lavage lymphocytes from asthma patients

BACKGROUND

Lymphocytes play a key role in asthma pathophysiology, secreting various cytokines involved in chronic inflammation. CHF6001 is a highly potent and selective phosphodiesterase type 4 (PDE4) inhibitor designed for inhaled administration and has been shown to reduce the late asthmatic response. However, the effect of PDE4 inhibition on the different cytokines produced by lung lymphocytes from asthma patients has not been examined.

METHODS

This study investigated the anti-inflammatory effects of CHF6001 and the corticosteroid, 17-BMP, on T-cell receptor (TCR) stimulated Th1, Th2 and Th17 cytokine release from bronchoalveolar lavage (BAL) cells from mild (n = 12) and moderate asthma (n = 12) patients.

RESULTS

CHF6001 inhibited IFNγ, IL-2 and IL-17, but not IL-13, secretion from both mild and moderate asthma patient BAL cells; there was a greater effect on IFNγ and IL-2 than IL-17. The corticosteroid inhibited all four cytokines from both patient groups, but was less effective in cells from more severe patients. CHF6001 had a greater inhibitory effect on IFNγ and IL-2 than 17-BMP.

CONCLUSION

The PDE4 inhibitor CHF6001 had a greater effect on Th1 cytokines from TCR-stimulated BAL cells than corticosteroid. This pharmacological effect suggests the therapeutic potential for PDE4 inhibitors to be used in the subset of more severe asthma patients with increased airway levels of IFNγ.

High levels of eukaryotic Initiation Factor 6 (eIF6) are required for immune system homeostasis and for steering the glycolytic flux of TCR-stimulated CD4+ T cells in both mice and humans

Eukaryotic Initiation Factor 6 (eIF6) is required for 60S ribosomal subunit biogenesis and efficient initiation of translation. Intriguingly, in both mice and humans, endogenous levels of eIF6 are detrimental as they act as tumor and obesity facilitators, raising the question on the evolutionary pressure that maintains high eIF6 levels. Here we show that, in mice and humans, high levels of eIF6 are required for proper immune functions. First, eIF6 heterozygous (het) mice show an increased mortality during viral infection and a reduction of peripheral blood CD4⁺ Effector Memory T cells. In human CD4⁺ T cells, eIF6 levels rapidly increase upon T-cell receptor activation and drive the glycolytic switch and the acquisition of effector functions. Importantly, in CD4⁺ T cells, eIF6 levels control interferon-γ (IFN-γ) secretion without affecting proliferation. In conclusion, the immune system has a high evolutionary pressure for the maintenance of a dynamic and powerful regulation of the translational machinery.

Chronic thoracic spinal cord injury impairs CD8+ T-cell function by up-regulating programmed cell death-1 expression

Background

Chronic spinal cord injury (SCI) induces immune depression in patients, which contributes to their higher risk of developing infections. While defects in humoral immunity have been reported, complications in T-cell immunity during the chronic phase of SCI have not yet been explored.

Methods

To assess the impact of chronic SCI on peripheral T-cell number and function we used a mouse model of severe spinal cord contusion at thoracic level T9 and performed flow cytometry analysis on the spleen for T-cell markers along with intracellular cytokine staining. Furthermore we identified alterations in sympathetic activity in the spleen of chronic SCI mice by measuring splenic levels of tyrosine hydroxylase (TH) and norepinephrine (NE). To gain insight into the neurogenic mechanism leading to T-cell dysfunction we performed in vitro NE stimulation of T-cells followed by flow cytometry analysis for T-cell exhaustion marker.

Results

Chronic SCI impaired both CD4⁺ and CD8⁺ T-cell cytokine production. The observed T-cell dysfunction correlated with increased expression of programmed cell death 1 (PD-1) exhaustion marker on these cells. Blocking PD-1 signaling in vitro restored the CD8⁺ T-cell functional defect. In addition, we showed that chronic SCI mice had higher levels of splenic NE, which contributed to the T-cell exhaustion phenotype, as PD-1 expression on both CD4⁺ and CD8⁺ T-cells was up-regulated following sustained exposure to NE in vitro.

Conclusions

These studies indicate that alteration of sympathetic activity following chronic SCI induces CD8⁺ T-cell exhaustion, which in turn impairs T-cell function and contributes to immune depression. Inhibition of the exhaustion pathway should be considered as a new therapeutic strategy for chronic SCI-induced immune depression.

Targeting co-stimulatory pathways in gene therapy

Gene therapy with recombinant viral vectors such as adenovirus and adenovirus-associated virus holds great promise in treating a wide range of diseases because of the high efficiency with which the viruses transfer their genomes into host cells in vivo. However, the activation of the host immune responses remains a major hurdle to successful gene therapy. Studies in the past two decades have elucidated the important role co-stimulation plays in the activation of both T and B cells. This review summarizes our current understanding of T cell co-stimulatory pathways, and strategies targeting these co-stimulatory pathways in gene therapy applications as well as potential future directions.

Effects of the phosphodiesterase IV inhibitor rolipram on Th1 and Th2 immune responses in mice

The present study was designed to investigate the effect of the phosphodiesterase IV inhibitor rolipram on Th1 and Th2 immune responses in mice. Mice were immunized subcutaneously at the base of the tail with ovalbumin (OVA) emulsified with complete Freund's adjuvant (day 0) and were treated daily with oral administration of various doses of rolipram from days 0 to 20. On day 21, production of anti-OVA IgG and proliferative responses to the antigen were determined. Anti-OVA IgG2a and interferon-γ (IFN-γ), as indicators of Th1 responses, and anti-OVA IgG1 and interleukin-10 (IL-10), as indicators of Th2 responses, were also measured. The results showed that treatment with rolipram failed to affect the production of OVA-specific IgG but decreased the proliferation of spleen cells to the antigen. Its inhibitory effect on these immune responses was correlated with a marked decrease in IFN-γ but not IL-10 production, although neither anti-OVA IgG2a nor IgG1 production was affected by rolipram. These results suggest that rolipram may preferentially inhibit Th1 responses more effectively than Th2 responses. Administration of rolipram resulted in suppression of antigen (OVA)-induced arthritis in mice. The suppression of joint inflammation by rolipram was associated with the inhibition of the OVA-specific proliferative responses of spleen cells and IFN-γ secretion. These results indicate that rolipram may be effective in regulating Th1-mediated diseases such as rheumatoid arthritis.

Characterization of sequence variations in immunodominant regions of the HBV-nucleocapsid protein as a prerequisite for the development of an epitope-based vaccine

BACKGROUND/AIMS

In hepatitis B virus infection, viral elimination is dependent on an efficient antiviral T cell response which is not detectable in chronic hepatitis B. Therefore, new therapeutic concepts focus on T cell activation, such as epitope-based T cell-targeted vaccines. However, with the development of peptide-based vaccines in mind, viral mutations frequently described in hepatitis B within known immunodominant helper epitopes may have an influence on peptide selection.

METHODS

Mutant peptides within immunodominant epitopes (aa 1-20, aa 91-105, and aa 143-157) at position 12, 14, 93, 97, 147, 151, 153, and 155 were tested with peripheral blood mononuclear and specific clone cells for their ability to induce proliferation, produce cytokines, induce T cell receptor down-regulation or antagonize wild-type activity of the hepatitis B core antigen-specific CD4+ T cell clones.

RESULTS

Five variants could not induce T cell proliferation or cytokine production when the variants were presented alone. Coincubation with wild-type epitopes leads to T cell activation showing that the variants do not act as T cell receptor antagonists for hepatitis B virus-specific CD4+ T cells. In contrast, five other variants and wild-type peptides stimulated CD4+ T cell proliferation and production of Th1 cytokines.

CONCLUSIONS

Our data demonstrate that frequently occurring mutations within immunodominant epitopes have rather a nonstimulatory than a strengthening effect and thus should not included in a vaccine.

Cross-talk between G(s)- and G(q)-coupled pathways in regulation of interleukin-4 by A(2B) adenosine receptors in human mast cells

Human mast cells express functional A(2A) and A(2B) adenosine receptors. However, only stimulation of A(2B), not A(2A), leads to secretion of interleukin (IL)-4, an important step in adenosine receptor-mediated induction of IgE synthesis by B-cells. In this study, we investigate intracellular pathways that link stimulation of A(2B) receptors to IL-4 up-regulation in HMC-1 mast cells. Both A(2A) and A(2B) receptors couple to G(s) proteins and stimulate adenylate cyclase, but only A(2B) stimulates phospholipase Cbeta through coupling to G(q) proteins leading to activation of protein kinase C and calcium mobilization. Inhibition of phospholipase Cbeta completely blocked A(2B) receptor-dependent IL-4 secretion. The protein kinase C inhibitor 2-{8-[(dimethylamino)-methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-(1-methyl-1H-indol-3-yl)maleimide (Ro-32-0432) had no effect on A(2B) receptor-mediated IL-4 secretion but inhibited phorbol 12-myristate 13-acetate-stimulated IL-4 secretion. In contrast, chelation of intracellular Ca(2+) inhibited both A(2B) receptor- and ionomycin-dependent IL-4 secretion. This Ca(2+)-sensitive pathway probably includes calcineurin and nuclear factor of activated T cells, because A(2B) receptor-dependent IL-4 secretion was blocked with cyclosporin A or 11R-VIVIT peptide. G(s)-linked pathways also play a role in the A(2B) receptor-dependent stimulation of IL-4 secretion; inhibition of adenylate cyclase or protein kinase A attenuated A(2B) receptor-dependent IL-4 secretion. Although stimulation of adenylate cyclase with forskolin did not increase IL-4 secretion on its own, it potentiated the effect of Pasteurella multocida toxin by 2-fold and ionomycin by 3-fold. Both forskolin and stimulation of A(2B) receptors up-regulated NFATc1 protein levels. We conclude that A(2B) receptors up-regulate IL-4 through G(q) signaling that is potentiated via cross-talk with G(s)-coupled pathways.

Peripheral blood mononuclear cells proliferation and Th1/Th2 cytokine production in response to streptococcal M protein in psoriatic patients

BACKGROUND

Psoriasis is a chronic skin disease that is probably a T cell-mediated autoimmune condition which is strongly associated with streptococcal throat infections. Although some groups have associated the involved response with different streptococcal antigens, M protein has been described as the major virulence factor of Streptococcus pyogenes. Thus, it is necessary to describe some features of the cellular responses to this streptococcal antigen.

METHODS

Proliferation and Th1/Th2 cytokine production of peripheral blood mononuclear cells (PBMC) in response to total soluble extracts from type M5 S. pyogenes with (TSE37Sp) and without (M(-)TSESp) M protein were analyzed in 10 psoriatic patients and 10 healthy controls.

RESULTS

PBMC from both patients and controls proliferated to both extracts. Responses to M(-)TSESp were significantly lower than those to TSE37Sp (P < 0.05). PBMC IL-2 and gammaIFN production after TSE37Sp stimulus was much higher than after M(-)TSESp antigenic stimulation in both groups (P < 0.05). Meanwhile, IL-4 production was quite low in both groups and in response to both extracts. We found a differential production of IL-10 between groups. PBMC from healthy controls responded to TSE37Sp with a much higher production of this cytokine as compared to the responses showed to M(-)TSESp while the cells from psoriatic patients responded without differences in the production of IL-10.

CONCLUSION

Results obtained suggest an important Th1 response to M protein in psoriatic patients which could be associated with the cellular responses involved in psoriasis, while healthy subjects respond in a probably non-Th2 IL-10 producing regulatory T cells fashion.

Renal tubular epithelial cells modulate T-cell responses via ICOS-L and B7-H1

BACKGROUND

Renal tubular epithelial cells (TECs) play an active role in renal inflammation. Previous studies have demonstrated the capacity of TECs to modulate T-cell responses both positively and negatively. Recently, new costimulatory molecules [inducible T cell costimulator-L (ICOS-L) and B7-H1] have been described, which appear to be involved in peripheral T-cell activation.

METHODS

We characterized expression and regulation of costimulatory molecules on primary human TECs and the TEC line human kidney-2 (HK-2) with reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry. Immunohistochemistry was performed on human kidney biopsies. The capacity of TECs to modulate T-cell activation was studied in TEC/T-cell cultures.

RESULTS

We demonstrate that TECs express ICOS-L and B7-H1 in vitro and in vivo. Stimulation with interferon-gamma (IFN-gamma) resulted in increased expression of B7-H1, whereas ICOS-L expression was marginally increased upon stimulation with CD40L, with no effect of interleukin (IL-1), IL-17, or tumor necrosis factor-alpha (TNF-alpha). Furthermore, we show that TECs are able to costimulate T cells that have received signal-1 using alphaCD3 antibodies, inducing strong IL-10 production, which was partially mediated by ICOS-L. In contrast, B7-H1 appeared to be involved in inhibition of proliferation and cytokine synthesis. In addition, TECs were able to alter the cytokine profile of fully activated T cells, which were incubated with alphaCD3 and alphaCD28 antibodies, resulting in low IFN-gamma and high IL-10 production. This activity appeared to be independent of ICOS-L and B7-H1.

CONCLUSION

Interaction of tubular epithelial cells and kidney infiltrating T cells via ICOS-L and B7-H1 may change the balance of positive and negative signals to the T cells, leading to IL-10 production and limitation of local immune responses.

Effect of Rolipram, a Phosphodiesterase IV Inhibitor, on Allergic Footpad Swelling using Various Adjuvants in Mice

We studied the effect of rolipram, a phosphodiesterase (PDE) IV inhibitor, on allergic footpad swelling in mice. For this study, varying adjuvants including complete Freund's adjuvant (CFA), incomplete Freund's adjuvant (IFA) and Imject Alum (Alum) were used because the extent of antigen-specifically induced T helper type 1 (Th1) and Th2 responses had been shown to depend on adjuvants used. To induce allergic footpad swelling, we immunized mice with ovalbumin (OVA) emulsified in either CFA or IFA, dissolved in Alum or in phosphate-buffered saline (PBS) as a control (day 0), followed by subcutaneous injection of the antigen into footpads on day 21. Rolipram was given orally to the animals daily from days 0-20. Results showed that treatment with rolipram was followed by an increase in early swelling at 0.5 h and a decrease in late swelling at 6 and 24 h in the CFA group. In the IFA group, rolipram significantly enhanced swelling at, but not after, 30 min. In the Alum and the PBS groups, the PDE inhibitor failed to affect the OVA-specific footpad reaction at all times examined. Treatment of the CFA and IFA groups with rolipram significantly inhibited the production of the Th1 antibody anti-OVA immunoglobulin G2a (IgG2a), and the drug enhanced Th2 cell-dependent anti-OVA IgE production. In both groups, rolipram also enhanced the secretion of Th2 cytokines including interleukin-4 (IL-4) and IL-10. These findings suggest that rolipram may facilitate early allergic footpad swelling mediated by Th2 immune responses, while the late phase of swelling associated with Th1 responses may be attenuated by the PDE IV inhibitor.

Macrophages and post-burn immune dysfunction

The activation of a pro-inflammatory cascade after burn injury appears to be important in the development of subsequent immune dysfunction, susceptibility to sepsis and multiple organ failure. Macrophages are major producers of pro-inflammatory mediators and their productive capacity for these mediators is markedly enhanced following thermal injury. Thus, macrophage hyperactivity (as defined by increased productive capacity for pro-inflammatory mediators) appears to be of critical importance in the development of post-burn immune dysfunction. This review will focus on the current state of knowledge with regards to the role of macrophages in the development of post-burn immune dysfunction. Particular areas of discussion include: nitric oxide synthase (NOS) and cyclooxygenase (COX) enzyme systems, macrophages and the T-helper (Th)-1/Th-2 cytokine responses, alterations in macrophages signal transduction and a potential role for gamma/delta T-cells in the development of macrophage hyperactivity following thermal injury. A more comprehensive understanding of the relationship between macrophage activity and post-burn immune dysfunction will hopefully provide the basis for improved therapeutic regimes in the treatment of burn patients.

Differential expression and tissue compartmentalization of the inflammatory response following thermal injury

Studies have shown that both animal tissue-fixed immune cells and human peripheral blood mononuclear cell (PBMC) functions are altered after burn injury. Additional studies suggest that the burn injury-induced alterations in these divergent cell populations from different species are similar. It remains unknown, however, whether the observed changes in animal tissue-fixed immune cell function following thermal injury also occurs to a similar extent in the PBMC population. The aim of our study was to compare PBMC and tissue-fixed immune cell functions from the same animal using a murine burn model. At 7 days post-burn, mice were more susceptible to sepsis and delayed type hypersensitivity responses were suppressed. Splenocytes isolated from injured mice displayed suppressed proliferation and increased IL-10 production. In contrast, PBMC from injured mice displayed suppressed proliferation, IL-2 and IFN-gamma production. Splenic macrophage nitric oxide, PGE(2), TNF-alpha, IL-6 and IL-10 production was enhanced post-burn and IL-12 production was suppressed. PBMC from such animals displayed enhanced PGE(2) production and suppressed IL-6 and IL-12 production. These results indicate that while an immunosuppressive Th(2) phenotype (increased IL-10 and/or suppressed IL-2, IFN-gamma) was induced in both the splenic and PBMC compartments post-injury, differential expression and dimorphism in the response also exists. Thus, the assessment of only PBMC function in burn patients may not accurately reflect the patient's actual immune status at the tissue level.

Cyclooxygenase 2-mediated suppression of macrophage interleukin-12 production after thermal injury

Macrophage (Mphi) prostaglandin (PG)E(2) production has been implicated in immunosuppression and increased susceptibility to sepsis after thermal injury. Deficient interleukin (IL)-12 production has also been implicated in these postburn complications. The present study examined the relationship between Mphi cyclooxygenase (COX)-2 activity and IL-12 production after thermal injury. C57BL/6 female mice were subjected to a 25% total body surface area full-thickness burn. Mphi were isolated 7 days later, or the mice were subjected to sepsis by cecal ligation and puncture (CLP). IL-12 production by Mphi from injured mice was suppressed by >50%, whereas COX-2 expression and PGE(2) production were increased twofold. The COX-2 inhibitor NS-398 suppressed PGE(2) production and normalized IL-12 production in the injury group, whereas it had no effect on IL-10 production. Injured mice subjected to CLP had lower IL-12 plasma levels compared with sham-treated mice subjected to CLP. NS-398 treatment prevented the suppression in plasma IL-12 levels in the injury group. Thus elevated Mphi COX-2 activity, independent of IL-10, suppresses Mphi IL-12 production after thermal injury and may play an important role in the observed immunosuppression under such conditions.

Histamine increases the expression of LOX-1 via H2 receptor in human monocytic THP-1 cells

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a member of the scavenger receptor family, and is known to be expressed in monocytes/macrophages. We investigated the effect of histamine on the expression of LOX-1 in cells of the human monocytic leukemia cell line THP-1. Histamine as well as forskolin and dibutyryl cyclic AMP (Bt2-cAMP) stimulated the THP-1 monocytes to express the LOX-1 gene at the transcription level. This histamine effect on LOX-1 gene expression, via the histamine H2 receptor-mediated cAMP signal transduction pathway, was reduced after differentiation of the cells into macrophages, even though forskolin and Bt2-cAMP still enhanced the gene expression. The alteration of the responsiveness of LOX-1 expression to histamine was related to suppressed expression of the H2 receptor in THP-1 macrophages. The switch of the predominant class of histamine receptors between H1 and H2 would modulate the effects of histamine on LOX-1 gene expression in monocytes and macrophages, and therefore, would play a certain role in the inflammatory aspects of atherogenesis.

Selective inhibition of interleukin-4 gene expression in human T cells by aspirin

Previous studies indicated that aspirin (acetylsalicylic acid [ASA]) can have profound immunomodulatory effects by regulating cytokine gene expression in several types of cells. This study is the first in which concentrations of ASA in the therapeutic range were found to significantly reduce interleukin (IL)-4 secretion and RNA expression in freshly isolated and mitogen-primed human CD4+ T cells. In contrast, ASA did not affect IL-13, interferon-gamma, and IL-2 expression. ASA inhibited IL-4, but not IL-2, promoter-driven chloramphenicol acetyltransferase expression in transiently transfected Jurkat T cells. The structurally unrelated nonsteroidal anti-inflammatory drugs indomethacin and flurbiprofen did not affect cytokine gene expression in T cells, whereas the weak cyclo-oxygenase inhibitor salicylic acid was at least as effective as ASA in inhibiting IL-4 expression and promoter activity. The inhibitory effect of ASA on IL-4 transcription was not mediated by decreased nuclear expression of the known salicylate target nuclear factor (NF)-kappaB and was accompanied by reduced binding of an inducible factor to an IL-4 promoter region upstream of, but not overlapping, the NF of activated T cells- and NF-kappaB-binding P1 element. It is concluded that anti-inflammatory salicylates, by means of a previously unrecognized mechanism of action, can influence the nature of adaptive immune responses by selectively inhibiting the expression of IL-4, a critical effector of these responses, in CD4+ T cells.

Lymphocyte stimulation by CD3-CD28 enables detection of low T cell interferon-gamma and interleukin-4 production in rheumatoid arthritis

The analysis of cytokine production is increasingly important in defining the course of an immune response and in evaluating specific therapies of immune diseases. In rheumatoid arthritis (RA), a dysregulation in T1/T2 cell balance, as defined by the production of their specific cytokines, IFN-gamma and IL-4, respectively, is suggested. A predominance of T1-cell mediated macrophage activity in the joint plays a key role in the destruction of articular cartilage and subchondral bone, whereas local T2 cell activity, mitigating disease, fails. However, analysis of the cytokines defining both T cell subsets is difficult and spontaneous production is often below detection limits. Several stimuli are therefore used to increase cytokine production. In the present study we examined whether stimulation of peripheral blood T cells in the context of mononuclear cells (PB MNC) by CD3-CD28 is a reliable method for assessing IFN-gamma and IL-4 production and is representative for the spontaneous production of these cytokines. The production of IFN-gamma and IL-4 following CD3-CD28 stimulation of RA PB MNC correlated significantly in a ratio 1 : 1 with production following ionomycin-PMA stimulation. In samples with detectable spontaneous production of IFNgamma and IL-4, production following CD3-CD28 stimulation was significantly higher than in stimulated samples with undetectable spontaneous production. Moreover, in the case of spontaneous production there was a significant positive linear correlation between the CD3-CD28 stimulated and spontaneous IFNgamma and IL-4 production, although production of both cytokines was not equally enhanced. Serial sampling did not show significant daily or weekly variation in stimulated cytokine production. The results demonstrate that a pecific T-cell stimulation by CD3-CD28 is a reliable way to enhance IFN-gamma and IL-4 production above the detection limit and so measure the T1/T2 cell balance in RA.

Suppression of anti-CD3-induced interleukin-4 and interleukin-5 release from splenocytes of Mesocestoides corti-infected BALB/c mice by phosphodiesterase 4 inhibitors

We investigated the suppressive effects of rolipram, RP 73401 (piclamilast), and other structurally diverse inhibitors of adenosine 3'5'-cyclic monophosphate (cAMP)-specific phosphodiesterase (PDE4) on anti-CD3-stimulated interleukin (IL)-4 and IL-5 generation by splenocytes from BALB/c mice infected with Mesocestoides (M) corti. RP 73401 (IC40: 0.011 +/- 0.004 microM) was a very potent inhibitor of anti-CD3-induced IL-4 release, being approximately 40-fold more potent than (+/-)-rolipram (IC40: 0.43 +/- 0.09 microM). A maximal inhibition of 60-70% of the response was achieved at the top concentrations of RP 73401 (1 microM) and rolipram (100 microM). These PDE inhibitors also suppressed IL-5 generation over the same concentration ranges, but the maximal suppression achieved was only 30-40%. R-(-)-rolipram (IC40: 0.39 +/- 0.09 microM) was approximately 6-fold more potent than S-(+)- rolipram (IC40: 2.6 +/- 0.95 microM) in inhibiting IL-4 release. A close correlation (r2 = 0.82) was observed between suppression of IL-4 release by PDE inhibitors and inhibition of CTLL cell PDE4, a form against which R-(-)-rolipram displayed relatively weak inhibitory potency. A poorer correlation (r2 = 0.26) was observed between suppression of IL-4 release and affinities of cAMP PDE inhibitors for the high-affinity rolipram binding site in mouse brain membranes. The cGMP-inhibited PDE (PDE3) inhibitor, siguazodan, had little or no effect (IC40 > 100 microM) on anti-CD3-stimulated release of either IL-4 or IL-5 and did not significantly enhance the inhibitory action of RP 73401 on the release of either of these cytokines. Finally, RP 73401 (IC50: 0.41 +/- 0.19 nM) inhibited anti-CD3-stimulated DNA synthesis in splenocyte preparations from M. corti-infected mice and siguazodan (10 microM) had no effect on this response, either alone or in combination with the PDE4 inhibitor. The results show that PDE4 inhibitors suppress the release of Th2 cytokines from anti-CD3-stimulated murine spenocytes and that this effect is correlated with inhibition of a low-affinity PDE4 form.

Specific inhibition of TH2-type cytokine production from human peripheral T cells by terfenadine in vitro

BACKGROUND

Cytokine imbalance is thought to be one of the causes for allergic diseases. The effect of anti-allergic drugs on cytokine production from T cells should be examined in a convenient way.

OBJECTIVES

To study the in vitro effect of terfenadine, a prototype non-sedating H1 receptor antagonist, on cytokine production from activated T cells.

METHODS

T cells were cultured in the presence of terfenadine on anti-CD3 mAb and anti-CD26 mAb-coated wells, anti-CD3 mAb and anti-CD28 mAb-coated wells, and anti-CD3 mAb wells with PMA. T-cell proliferation, along with the concentrations of interleukin (IL) -2, interferon (IFN) -gamma, IL-4, and IL-5 were measured.

RESULTS

Terfenadine inhibited T-cell proliferation and IL-4 and IL-5 production under each costimulatory condition tested, whereas it had no effect on IL-2 and IFN-gamma production.

CONCLUSIONS

These results indicate that terfenadine has a specific inhibitory effect on TH2-type cytokine production induced by several ways of costimulatory activation.

Effects of tumour necrosis factor alpha and melphalan on the cytokine production of circulating T cells in patients with cancer

BACKGROUND

The objective of the present study was to investigate the effects of isolated limb perfusion (ILP) with tumour necrosis factor alpha (TNF-alpha) and melphalan on circulating T cells from cancer patients using two different methods.

DESIGN

Eight patients undergoing an ILP entered the study. At first, the number of T cells at several time points was determined using FACScan. Subsequently, production of interferon gamma (IFN-gamma) (T-helper 1) and interleukin (IL) 4 (T-helper 2) was measured at the intracytoplasmic level after stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. IFN-gamma, IL-4 and IL-2 (also T-helper 1) production in the whole-blood cell culture system was then determined after stimulation with a combination of anti-CD3/anti-CD28 monoclonal antibodies.

RESULTS

An enormous decrease in the number of circulating T cells was observed. In the remaining T-cell population cytokine production (IL-2, IL-4, IFN-gamma) was depressed, showing the same pattern in both methods. No difference could be detected between the effect of TNF-alpha and melphalan on Th1 cells and Th2 cells.

CONCLUSIONS

The results demonstrate that TNF-alpha and melphalan reduce the number of circulating T cells and at the single-cell level decrease cytokine production in the remaining circulating T cells. No selective effect of TNF-alpha on Th1 or Th2 cells could be detected. If the impaired T-cell function is representative of all T cells remaining in the systemic circulation, this could help to explain the tolerability of high TNF concentrations after ILP, perhaps by decreasing the synthesis and production of T-cell-derived cytokines.

Involvement of protein kinase A in histamine-mediated inhibition of IL-2 mRNA expression in mouse splenocytes

The release of histamine from mast cells and basophils during allergic reactions can regulate functions of T cells and may influence the nature of the immune response to a given antigen. The effects of histamine on T lymphocytes are associated with its binding to H2-receptors linked with adenylate cyclase, elevation of cAMP levels and activation of cAMP-dependent protein kinase (PKA). In this report we explore the role of PKA in histamine-mediated effects on IL-2 mRNA expression and IL-2 protein secretion. Fresh isolated mouse splenocytes (C57Bl/6) were pretreated with histamine (10(-4) M) for 1 h in the presence or absence of Rp-cAMPS (50 microM), an inhibitor of PKA regulatory subunit. The cells were then washed thoroughly and activated with plate-bound anti-CD3 (5 microg/ml), or PHA (1:100) or PMA + ionomycin (10 ng/ml, 1 microg/ml) for 6 h. Pretreatment with histamine inhibited IL-2 mRNA expression and secretion in cells activated with anti-CD3 or PMA, but not in cells activated with PMA + ionomycin. Rp-cAMPS prevented histamine-mediated suppression and did not itself affect IL-2 production. These results provide evidence that histamine affected IL-2 production when the cells were activated via the T cell receptor (TCR)/CD3 complex, but did not interfere with signal transduction pathways downstream of PKC leading to production of IL-2. These effects of histamine on IL-2 secretion and mRNA expression were mediated via PKA.

EBV-Induced Expression and HLA-DR-Restricted Presentation by Human B Cells of αB-Crystallin, a Candidate Autoantigen in Multiple Sclerosis

The development of multiple sclerosis is most likely influenced by autoimmune responses to central nervous system myelin proteins as well as by infections with common viruses such as EBV and human herpesvirus-6. However, much remains to be established on how these factors interact. In this study, we show that upon EBV infection, human B cells start to express αB-crystallin, a small stress protein that was identified previously as an immunodominant Ag of CNS myelin in multiple sclerosis patients. EBV-induced expression of αB-crystallin in B cells leads to HLA-DR-restricted presentation of the protein and to activation of proinflammatory αB-crystallin-specific Th cells. While αB-crystallin is present in EBV-infected human B cells, the protein is absent from human lymphoid tissues under normal conditions. This is in sharp contrast to other stress proteins such as heat-shock protein (hsp)27 and hsp60 that are ubiquitously expressed in these tissues. In addition, the absence of αB-crystallin from lymphoid tissues in humans is unique as compared with other mammals. All other species examined, including rodents, sheep, and primates, showed constitutive expression of αB-crystallin in secondary lymphoid tissues and sometimes even in the thymus. Since constitutive lymphoid expression most likely results in immunologic tolerance, such a state of tolerance to αB-crystallin can be expected for all of these species, but not for humans. When taken together, our data provide evidence for a novel mechanism by which common viral infections can trigger myelin-directed autoimmunity in a way that is unique for humans.

The immune suppressive effect of dexamethasone in rheumatoid arthritis is accompanied by upregulation of interleukin 10 and by differential changes in interferon gamma and interleukin 4 production

OBJECTIVES

The influence of dexamethasone on interleukin 10 (IL10) production and the type 1 (T1)/type 2 (T2) T cell balance found in rheumatoid arthritis (RA) was studied.

METHODS

Peripheral blood mononuclear cells (PB MNC) were isolated from 14 RA patients both before and 7 and 42 days after high dose dexamethasone pulse therapy. The ex vivo production of IL10, interferon gamma (IFN gamma) (T1 cell), and IL4 (T2 cell) by PB MNCs was assessed, along with parameters of disease activity (erythrocyte sedimentation rate, C reactive protein, Visual Analogue Scale, Thompson joint score). In addition, the in vitro effect of dexamethasone (0.02, 0.2, and 2 microM) on PB MNC IL10, IFN gamma, and IL4 production was studied.

RESULTS

Dexamethasone pulse therapy resulted in a rapid and sustained decrease in RA disease activity. IL10 production increased after dexamethasone treatment and this was sustained for at least six weeks. A transient strong decrease in IFN gamma was seen shortly after corticosteroid treatment, while IL4 only decreased slightly. This led to an increased IL-4/IFN gamma ratio. In vitro, IL10 production was not detectable, IFN gamma and IL4 decreased, but the effect was more pronounced for IFN gamma than for IL4, which again resulted in an increased IL4/IFN gamma ratio.

CONCLUSION

Dexamethasone therapy in RA patients leads to a rapid, clinically beneficial effect. The upregulation of IL10 production may be involved in the prolonged clinical benefit. The strong immunosuppressive effect is most evident in the decrease in IFN gamma, and is therefore accompanied by a relative shift towards T2 cell activity. In vitro evaluation showed that this shift in T cell balance was a direct effect of dexamethasone and thus independent of the hypothalamic-pituitary-adrenal axis.

Histamine inhibits the production of interleukin-12 through interaction with H2 receptors

IL-12 is essential for T helper 1 (Th1) development and inhibits the induction of Th2 responses. Atopic diseases, which are characterized by Th2 responses, are associated with the overproduction of histamine. Here we present evidence that histamine, at physiological concentrations, strongly inhibits human IL-12 p40 and p70 mRNA and protein production by human monocytes. The use of specific histamine receptor antagonists reveals that this inhibition is mediated via the H2 receptor and induction of intracellular cAMP. The inhibition of IL-12 production is independent of IL-10 and IFN-gamma. The observation that histamine strongly reduces the production of the Th1-inducing cytokine IL-12 implies a positive feedback mechanism for the development of Th2 responses in atopic patients.

Effects of anti-IL-4 receptor monoclonal antibody on in vitro T cell cytokine levels: IL-4 production by T cells from non-atopic donors

IL-4 is a pleiotropic cytokine which is involved in the development of atopic diseases. Only limited data exist on IL-4 production in humans, and the relative contribution to atopy of either unbalanced IL-4 production, or increased IL-4-responsiveness of target cells, is still unknown. The use of a MoAb to the IL-4 receptor alpha-chain (IL-4Ralpha) enabled us to demonstrate that IL-4 production in vitro is usually underestimated, due to in vitro consumption, even in cultures of purified T cells. When IL-4 consumption was blocked, it became evident that CD80 and CD86 both provide effective costimulatory signals for high IL-4 production. Moreover, we found that even stimulation with a soluble antigen (tetanus toxoid) induces IL-4 production by T cells from healthy non-atopic donors. Both sets of data imply that IL-4 is not required for IL-4 production by memory and/or effector T cells. Our data further show that endogenous IL-4 activity modulates IL-10 and interferon-gamma production by T cells in opposite directions. The use of this receptor-blocking antibody will thus be helpful for in vitro studies on IL-4 regulation. Consumption of IL-4 by different cell types during in vitro cultures might have interfered with previous attempts to quantify IL-4 production by human T cells.

Human memory T cell differentiation into Th2-like effector cells is dependent on IL-4 and CD28 stimulation and inhibited by TCR ligation

Freshly isolated memory T cells primarily produced IL-2 and small amounts of IL-4 and IFN-gamma after stimulation in vitro. Priming for 5 days in vitro with anti-CD28 monoclonal antibodies (mAb) alone markedly increased production of IL-4. In comparison to fresh cells, the increase in the amount of IL-4 secreted reflected a marked increase in the number of IL-4-producing cells. Stimulation with immobilized anti-CD3 mAb during priming limited subsequent IL-4 production. By contrast, IFN-gamma production from in vitro primed memory T cells was directly correlated to the concentration of priming anti-CD3 mAb. IL-2 production by all restimulated cells was decreased. The differentiation of IL-4-producing cells could be blocked by antibody to IL-4 and enhanced by the addition of recombinant IL-4 as well as antibody to IFN-gamma. Of note, the IL-4-producing effector cells induced from in vitro priming derived from the early CD27pos memory T cell subset, whereas the small CD27neg differentiated memory subset produced IL-4 without in vitro priming. The results indicate that memory T cells can be directed to differentiate into IL-4-producing effector cells by stimulation via CD28 and IL-4, whereas increasing engagement of the TCR limits Th2 memory cell differentiation.

Mutual antagonism of rheumatoid arthritis and hay fever; a role for type 1/type 2 T cell balance

OBJECTIVES

The balance between interferon gamma (IFN gamma) and interleukin 4 (IL4) producing T cells (T1 and T2 cells) seems to be of importance in many (auto)immune disorders. In general, T1 cell activity is important in cellular immunity whereas T2 cell activity plays a part in humoral responses. T1 cell activity predominates in joints of patients with rheumatoid arthritis (RA) whereas T2 cell activity is characteristic of atopic syndromes. This study investigated whether the prevalence of hay fever in RA is low and if severity of RA (T1 cell activity) can be influenced by the concomitant occurrence of a T2 cell mediated disease (hay fever).

METHODS

The prevalence of hay fever was assessed in 643 consecutive (RA and non-RA) patients seen in our outpatient clinic and confirmed by skin test and specific IgE. Of this group the 12 RA patients with hay fever were compared with RA patients without hay fever (matched for age, sex, and disease duration).

RESULTS

The prevalence of hay fever in RA patients is lower than in non-RA patients (4% versus 8%), and yields a relative risk for RA patients to develop hay fever of 0.48. RA patients with hay fever showed a lower disease activity (erythrocyte sedimentation rate, C reactive protein, Thompson joint score, and radiographic joint damage (Sharp) score) than RA patients without hay fever. The clinical data were related to peripheral blood T1/T2 cell balance: a lower IFN gamma/IL4 ratio was observed for RA patients with hay fever, indicating a comparatively increased T2 cell activity in RA patients with hay fever.

CONCLUSION

These results argue in favour of the exploration of treatments aimed at regulation of a possible imbalance in T1/T2 cell activity in RA.

Inhibition of T Cell Activation by Pharmacologic Disruption of the MEK1/ERK MAP Kinase or Calcineurin Signaling Pathways Results in Differential Modulation of Cytokine Production

Productive T cell activation leading to cytokine secretion requires the cooperation of multiple signaling pathways coupled to the TCR and to costimulatory molecules such as CD28. Here, we utilized two pharmacophores, PD98059 and FK506, that inhibit, respectively, mitogen-activated protein (MAP) kinase kinase 1 (MEK 1) and calcineurin, to determine the relative role of the signaling pathways controlled by these enzymes in T cell activation. Although the two compounds had distinctive effects on CD69 induction, they both suppressed T cell proliferation induced by anti-CD3 mAb, in a manner reversible by exogenous IL-2, suggesting that PD98059, like FK506, affects the production of, rather than the responsiveness to growth-promoting cytokines. Accordingly, IL-2 production by T cells stimulated with anti-CD3 mAb in conjunction with PMA or with anti-CD28 mAb was inhibited by both compounds. However, these compounds differentially affected the production of other cytokines, depending on the mode of activation. PD98059 inhibited TNF-α, IL-3, granulocyte-macrophage (GM)-CSF, IFN-γ, and to a lesser extent IL-6 and IL-10 production but enhanced IL-4, IL-5, and IL-13 production induced by CD3/PMA or CD3/CD28. FK506 suppressed CD3/PMA-induced production of all cytokines examined here but to a lesser extent IL-13. FK506 also reduced CD3/CD28-induced production of IL-3, IL-4, IL-10, TNF-α, and IL-6 but augmented that of GM-CSF, IL-5, IFN-γ, and IL-13. Therefore, the biochemical targets of PD98059 and FK506 contribute differently to the production of various cytokines by T cells, which may have implications for the therapeutic manipulation of this production.

Protein kinase A inhibitors reverse histamine-mediated regulation of IL-5 secretion

Histamine and IL-5 are important autacoid mediators involved in the etiology of allergic diseases. IL-5 is the main factor of eosinophilic reactions in allergy. It has been suggested that the protein kinase A-dependent (PKA) pathway of signal transduction may play the main role in histamine-induced elevation of interleukin-5 production. This study was designed to investigate the effects of the inhibitors of regulatory and catalytic subunits of PKA on histamine-mediated elevation of IL-5 production. In our study, histamine at a concentration range of 10(-4)-10(-6) M enhanced IL-5 production in D10.G4.1 cells, a mouse Th2 helper cell line. Pretreatment of this cell line with histamine at a concentration of 10(-4) M for 6-9 h had the maximum stimulatory effects (226-420%) on IL-5 production. Other cAMP-elevating agents including forskolin and Bt2-cAMP produced similar effects. The PKA inhibitors N-[2-(methylaminoethyl]-5-isoquinoline-sulfonamide (H-8) and Rp-diastereomer of adenosine cyclic 3',5'-phosphorothioate (Rp-cAMPS) were used for the inhibition of catalytic and regulatory subunits of PKA, respectively. Pretreatment of D10.G4.1 cells with H-8 at a concentration of 10(-5) M completely prevented the effects of histamine at a concentration range of 10(-6)-10(-4) M. Rp-cAMPS at 10(-5) M also prevented histamine-induced stimulation. Neither inhibitor affected IL-5 production when tested alone. These observations suggest a role for PKA in histamine-mediated increase in IL-5 production.

Cytokine release and its modulation by dexamethasone in whole blood following exercise

Glucocorticoids (GC) play an important role in the treatment of inflammatory diseases like asthma. However, in selected patients a relative resistance to GC has been reported. Recently, it has been suggested that GC sensitivity of peripheral blood leucocytes may be regulated in a dynamic fashion during exercise, in association with activation of the hypothalamic-pituitary-adrenal (HPA) axis. The aim of the present study was to explore changes in the GC sensitivity of cytokine production by leucocytes following strenuous exercise by well trained oarsmen. These changes were studied using lipopolysaccharide (LPS)-induced and anti-CD2/anti-CD28 MoAb-stimulated cytokine release in whole blood and its modulation by dexamethasone. Following exercise, significant decreases in LPS-induced release of IL-6, tumour necrosis factor-alpha (TNF-alpha) and IL-10 and anti-CD2/anti-CD28 MoAb-stimulated secretion of interferon-gamma (IFN-gamma) were observed. In addition, the inhibitory effect of dexamethasone on both IL-6 and TNF-alpha secretion was significantly reduced following exercise, whereas that on IL-10 and IFN-gamma release was not affected. These exercise-induced changes were accompanied by activation of the HPA axis, as indicated by an increase in circulating adrenocorticotropic hormone (ACTH) levels immediately following exercise. The results from the present study suggest that GC sensitivity of whole blood cytokine release can be regulated in a dynamic fashion and that this can be assessed using an ex vivo stimulation assay. Moreover, since dexamethasone responsiveness of anti-CD2/anti-CD28 MoAb-induced IFN-gamma secretion in whole blood is not affected by exercise, it may suggest that exercise differentially affects monocytes and lymphocytes. The dynamic regulation of steroid responsiveness of leucocytes, as observed in the present study, could have important consequences for the effectiveness of GC treatment in inflammatory diseases.

CD8+ T cells inhibit immunoglobulin E synthesis in low responder SJL/J mice

In an effort to examine the basis for low IgE responsiveness of SJL/J strain mice, we analysed the profiles of cytokines, such as interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma), in SJL/J and A.SW/SnJ mice following immunization. Splenocytes of ovalbumin (OVA)-immunized SJL/J mice, secreted significantly higher levels of IL-4 and lower levels of IFN-gamma than those of A.SW/SnJ mice. A time-course analysis of cytokine expression in in vitro cultures of spleen cells indicated that the levels of IL-4 and IL-2 remained persistently high throughout in the cultures of SJL/J splenocytes as opposed to those of A.SW/SnJ. Depletion of CD4+ T cells in vivo suppressed the production of IL-2, IL-4 and IFN-gamma suggesting that CD4 T cells are the producers of most cytokines in both SJL/J and A.SW/SnJ mice. Depletion of CD8+ T cells in vivo not only induced productive epsilon transcript but also enhanced IgE production in SJL/J mice. Moreover, CD8 depletion in SJL/J mice led to decreased production of IFN-gamma, resulting in a net decrease in the ratio of IFN-gamma to IL-4. A similar shift in the IFN-gamma/IL-4 ratio was found in splenocytes of SJL/J mice following irradiation, which is known to enhance IgE synthesis in these mice. Taken together, it is concluded that low IgE responsiveness in SJL/J mice is not due to a defect in IL-4 production per se. Increased IFN-gamma production by the CD8+ T cells inhibits class switch and suppresses IgE antibody production in SJL/J mice.

The role of IL-13 in IgE synthesis by allergic asthma patients

IgE antibodies play a crucial role in allergic type I reactions. Only IL-4 and IL-13 are able to induce an immunoglobulin isotype switch to IgE in B cells. A major question is to what extent these cytokines contribute to the production of IgE in allergic patients. To address this question we used an in vitro culture system in which the production of IgE is dependent on endogenously produced IL-4 and IL-13. In cultures of purified T and B cells from allergic asthma patients and non-atopic controls, T cells were polyclonally stimulated to obtain IL-4, IL-13 and subsequently IgE secretion. The absolute amount of IgE produced was not significantly different between patients and controls. When neutralizing IL-4 antibodies were included during culture, the production of IgE was dramatically inhibited in both patients and controls (production of IgE was reduced to 12%). However, neutralization of IL-13 led to a significantly stronger inhibition of IgE production in the patient group: production of IgE was reduced to 23 +/- 3% versus 50 +/- 10% in the control group. Corresponding with these results, we also observed a higher production of IL-13 by the patients, while the production of IL-4 was not significantly different. A more detailed analysis of the production of IL-13 revealed that patients' T cells were less sensitive to a negative signal controlling IL-13 production. Our results indicate that, at least in vitro, IgE production in allergic asthma patients is more dependent on IL-13 than in non-atopics, due to enhanced IL-13 production and to enhanced IgE production in response to IL-13.

Phenotypic and functional separation of memory and effector human CD8+ T cells

Human CD8+ memory- and effector-type T cells are poorly defined. We show here that, next to a naive compartment, two discrete primed subpopulations can be found within the circulating human CD8+ T cell subset. First, CD45RA-CD45R0(+) cells are reminiscent of memory-type T cells in that they express elevated levels of CD95 (Fas) and the integrin family members CD11a, CD18, CD29, CD49d, and CD49e, compared to naive CD8+ T cells, and are able to secrete not only interleukin (IL) 2 but also interferon gamma, tumor necrosis factor alpha, and IL-4. This subset does not exert cytolytic activity without prior in vitro stimulation but does contain virus-specific cytotoxic T lymphocyte (CTL) precursors. A second primed population is characterized by CD45RA expression with concomitant absence of expression of the costimulatory molecules CD27 and CD28. The CD8+CD45RA+CD27- population contains T cells expressing high levels of CD11a, CD11b, CD18, and CD49d, whereas CD62L (L-selectin) is not expressed. These T cells do not secrete IL-2 or -4 but can produce IFN-gamma and TNF-alpha. In accordance with this finding, cells contained within this subpopulation depend for proliferation on exogenous growth factors such as IL-2 and -15. Interestingly, CD8+CD45RA+CD27- cells parallel effector CTLs, as they abundantly express Fas-ligand mRNA, contain perforin and granzyme B, and have high cytolytic activity without in vitro prestimulation. Based on both phenotypic and functional properties, we conclude that memory- and effector-type T cells can be separated as distinct entities within the human CD8+ T cell subset.

Decrease in peripheral type 1 over type 2 T cell cytokine production in patients with rheumatoid arthritis correlates with an increase in severity of disease

OBJECTIVES

To compare peripheral type 1 (T1) and type 2 (T2) T cell activities in rheumatoid arthritis (RA) patients with that found for osteoarthritic (OA) patients and healthy controls and to correlate peripheral T1/T2 cell activity in RA with parameters of the disease.

METHODS

Peripheral blood mononuclear cells were isolated from patients with RA (n = 66), OA (n = 19), and healthy controls (n = 15). Primary T cell activity in these mononuclear cells was enhanced by means of anti-CD3/anti-CD28, which mimicks stimulation of T cells by activation of the T cell receptor and a major co-stimulatory signal. Interferon gamma (IFN gamma) production and interleukin 4 (IL4) production in the three groups were quantified as measures of T1 and T2 cell activity, respectively, and compared. Serum tumour necrosis factor alpha (TNF alpha), erythrocyte sedimentation rate (ESR), C reactive protein (CRP), and joint destruction assessed radiographically of RA patients were determined as parameters of disease activity and correlated with T1/T2 cell activity.

RESULTS

Peripheral T cells from RA patients produced significantly less IFN gamma and more IL4 than T cells from both age and sex matched OA patients and healthy controls. Moreover, in RA patients both a decrease in IFN gamma and an increase in IL4 production correlated with an increase in serum TNF alpha, ESR, CRP, and joint destruction.

CONCLUSIONS

These results suggest a role for differential T cell activity in RA. In view of the intra-articular T1 cell predominance the results might be explained by selective T1 cell migration into the joint or peripheral suppression of T1 cell activity.

Ligation of CD2 provides a strong helper signal for the production of the type 2 cytokines interleukin-4 and -5 by memory T cells

In this study, we investigated the efficiency of costimulatory signaling provided by anti-CD2 monoclonal antibodies (mAbs) for the production of type 1 (IL-2 and IFN-gamma) and type 2 (IL-4, IL-5, and IL-10) cytokines by human T cells. We cultured purified human T cells (freshly isolated from blood) with immobilized anti-CD3 mAb, either alone or in combination with anti-CD28 or anti-CD2 mAbs. When compared with the standard costimulatory signal anti-CD28, anti-CD2 mAbs (9-1 plus 9.6) were shown to be more potent costimulators of IL-4 production and to have similar activity for IL-5 production, but to be less potent for costimulation of IL-2, IL-10, and IFN-gamma production. IL-4 production was completely inhibited by cyclosporin A or by blocking IL-2 activity and its receptor. IL-4 and IL-5 were produced by CD45RO+ T cells but not by CD45RA+ T cells, indicating that anti-CD2 in this system costimulated type 2 cytokine production by differentiated memory cells. In the presence of IL-12, the cytokine profile was shifted to high IFN-gamma and IL-10 production and IL-4 and IL-5 production were slightly inhibited. Our data thus suggest that CD2 ligation plays an important role in the upregulation of Th2-like T cell activity (especially IL-4 production), but they also show that this effect is strongly modulated by IL-12, resulting in predominant IL-10 and IFN-gamma production instead.

Glucocorticoids inhibit human antigen-specific and enhance total IgE and IgG4 production due to differential effects on T and B cells in vitro

Although anti-inflammatory properties of glucocorticoids (GC) are well documented, their activity in allergic diseases is still controversial. Recently, it has been reported that GC can increase, both in vivo and in vitro, the polyclonal production of total IgE. In this study we investigated the effects of GC on the antigen (Ag)-specific IgE response in a human in vitro system with peripheral blood mononuclear cells or B cells of bee venom-sensitized individuals that allows the production of bee venom phospholipase A2 (PLA)-specific IgE and IgG4 antibodies (Ab). PLA-specific Ab were induced by simultaneously activating T cells and B cells specifically with allergen and polyclonally with anti-CD2 and soluble CD40 ligand (sCD40L) in the presence of interleukin (IL)-4. Indeed, dexamethasone and prednisolone enhanced the formation of total IgE and IgG4 in PBMC, while the production of PLA-specific IgE and IgG4 Ab was selectively inhibited in a dose-dependent manner. The suppressive effect of GC was mediated during Ag-specific stimulation and T cell-B cell interaction. This was due to GC suppressing specific T cell proliferation and cytokine production, whereas neither allergen-specific nor total IgE and IgG4 production by sCD40L/IL-4-stimulated pure B cells was affected. In contrast to GC, cyclosporine A inhibited both total and PLA-specific IgE and IgG4 secretion in peripheral blood mononuclear cells and B cell cultures. Further experiments showed that increase in nonspecific total isotype response resulted from inhibition of IL-4 uptake by cells other than B cells and sufficient availability of IL-4 to B cells for isotype switch and synthesis. Furthermore, demonstration of opposite regulatory effects of GC on specific and total isotype formation in vitro, including the inhibition of allergy-relevant Ag-specific IgE response, may contribute to a better understanding of apparently controversial observations, and explain why most allergic patients benefit from GC therapy.

Immunodominant CD4+ T-cell epitope within nonstructural protein 3 in acute hepatitis C virus infection

In acute hepatitis C virus infection, 50 to 70% of patients develop chronic disease. Considering the low rate of spontaneous viral clearance during chronic hepatitis C infection, the first few months of interaction between the patient's immune system and the viral population seem to be crucial in determining the outcome of infection. We previously reported the association between a strong and sustained CD4+ T-cell response to nonstructural protein 3 (NS3) of the hepatitis C virus and a self-limited course of acute hepatitis C infection. In this study, we identify an immunodominant CD4+ T-cell epitope (amino acids 1248 to 1261) that was recognized by the majority (14 of 23) of NS3-specific CD4+ T-cell clones from four of five patients with acute hepatitis C infection. This epitope can be presented to CD4+ T cells by HLA-DR4, -DR11, -DR12, -DR13, and -DR16. HLA-binding studies revealed a high binding affinity for 10 of 13 common HLA-DR alleles. Two additional CD4+ T-cell epitopes, amino acids 1388 to 1407 and amino acids 1450 to 1469, showed a very narrow pattern of binding to individual HLA-DR alleles. Our data suggest that the NS3-specific CD4+ T-cell response in acute hepatitis C infection is dominated by a single, promiscuous peptide epitope which could become a promising candidate for the development of a CD4+ T-cell vaccine.

Stimulation of suppressive T cell responses by human but not bacterial 60-kD heat-shock protein in synovial fluid of patients with rheumatoid arthritis

In several animal models of rheumatoid arthritis (RA), T cell responses to self 60-kD heat-shock protein 60 (hsp60) protect against the induction of arthritis. The nature of this suppressive T cell activity induced by self hsp60 is not clear. In the present study, T cell responses to human (self) hsp60 in RA in terms of type 1 (T1) and type 2 (T2) T cell activity were assessed. The results show that human and not bacterial hsp60-reactive synovial fluid (SF) T cells of patients with RA proliferate in the presence of the T2 cell growth factor IL-4. SF T cells stimulated with human hsp60 produced significantly lower amounts of IFN-gamma and higher amounts of IL-4 than SF T cells stimulated with bacterial hsp60 (P </= 0.002 and 0.05, respectively), and consequently a lower T1/T2 cell cytokine ratio was observed for human versus bacterial hsp60 (P </= 0.004). Additionally, human and not mycobacterial hsp60-specific T cell lines suppressed TNF-alpha production. Together, our results suggest that human hsp60, as overexpressed in inflamed synovium of patients with RA, can contribute to suppression of arthritis by the stimulation of regulatory suppressive T cell activity.

Differential regulation of IFN-gamma, IL-10 and inducible nitric oxide synthase in human T cells by cyclic AMP-dependent signal transduction pathway

Expression of cytokines by T lymphocytes is a highly balanced process, involving stimulatory and inhibitory intracellular signalling pathways. In the present work, we attempted to clarify the role of cAMP on interferon-gamma (IFN-gamma), interleukin (IL)-10, IL-4 and IL-13 expression as well as on the inducible nitric oxide synthase (iNOS) expression. Treatment of phytohaemagglutinin (PHA)/phorbol 12-myristate 13-acetate (PMA)-activated Jurkat cells with either dibutyryl-cyclic adenosine monophosphate (cAMP) or pentoxifylline induced a strong inhibition of IFN-gamma mRNA expression as measured by reverse transcription (RT)-polymerase chain reaction (PCR), without affecting IL-10 expression. Both cholera toxin and prostaglandin E2 (PGE2) induced a strong inhibition of IFN-gamma mRNA expression, whereas IL-10 mRNA expression was significantly enhanced. This differential regulation of IFN-gamma and IL-10 expression was related to intracellular cAMP concentration. IL-13 and IL-4 mRNA expressions were not inhibited. We developed a new method based on immunofluorescence for intracellular cytokine detection followed by optical and computerized image processing, and our results showed that IFN-gamma protein was strongly inhibited when cells were treated with PGE2 or dibutyryl (db)-cAMP, whereas IL-10 protein was enhanced. This suggests that cAMP exerts its action at both the transcriptional and protein levels. iNOS mRNA expression was markedly elevated in the presence of PGE2. The generation of nitric oxide using sodium nitroprusside (SNP) induced a dramatic decrease of IFN-gamma, while IL-10 was enhanced; and conversely the inhibition of iNOS activity using 1-NG-monomethyl arginine (1-NMMA) induced a clear inhibition of IL-10 and IL-4, while IFN-gamma was enhanced. These results provide evidence that the protein kinase A (PKA) activation pathway plays a prominent role in the balance between the type 1 and type 2 cytokine profile in PHA/PMA-activated Jurkat cells. Data also suggest that iNOS expression is under the control of PKA activation, and that NO seems to be able to assume the polarization of activated T cells to the type 2 profile.

Identification of transcription factor binding sites important in the regulation of the human interleukin-5 gene

This study identifies three regions of the human interleukin (IL)-5 promoter involved in binding nuclear factors from activated T cells. DNase I footprinting and mobility shift assays with nuclear proteins from the human T cell clone, SP-B21, demonstrated protein interactions with each of these response elements (REs), located between positions -79 and -45 (RE-I), -123 and -92 (RE-II), and -170 and -130 (RE-III). Two of these regions, RE-II and RE-III, have not previously been described to regulate IL-5 expression in T cells. The RE-II site was shown to be critical for inducible IL-5 promoter activity in transient transfection assays in D10.G4.1 T cells, while the RE-III site functions as a negative regulatory element. The activity of the RE-II site was specifically inhibited by cyclosporin A, and transfection assays with IL-5 constructs containing mutations in the RE-II site showed greatly reduced reporter gene activity. We have defined the sequence involved in stimulation-dependent transcription and have identified constitutive as well as inducible DNA-binding protein complexes that bind to RE-II. Antibodies against at least two members of the nuclear factor of activated T cells (NFAT) family of transcription factors are capable of binding to the IL-5 RE-II complexes, although they can be distinguished from previously identified NFAT-specific complexes by several characteristics.

Antigen-presenting cell-derived signals determine expression levels of CD70 on primed T cells

Interaction between CD27 and its ligand CD70 provides a second signal for T-cell proliferation and tumour necrosis factor-alpha (TNF-alpha) production. Whereas CD27 is broadly expressed during T-cell development, expression of CD70 in vivo is restricted. To determine when CD27 CD70 interactions can occur in immune reactions, we here analysed the regulation of CD70 expression on activated T cells. Mitogenic stimulation of purified T cells with either immobilized CD3 monoclonal antibody (mAb) or a combination of CD2 mAb induces only low levels of CD70 membrane expression. Markedly expression of the CD27-ligand is strongly enhanced by antigen-presenting cells (APC) and APC-associated signals such as interleukin-1 alpha (IL-1 alpha). IL-12, TNF-alpha and CD28-ligation. In contrast, T-cell derived cytokines, such as IL-4, counteract CD70 up-regulation on activated T cells. Analysis of the small subset of circulating CD70+ T cells revealed that these cells have a primed phenotype as they express CD45RO and HLA-DR antigens and are in high frequency able to secrete interferon-gamma (IFN-gamma). We conclude that T-T interactions involving CD27 and CD70 are likely to occur relatively early in immune reactions, after productive T-cell priming by APC and that expression of CD70 on circulating T cells is a reflection of recent priming by antigen.

Anergic TH1 clones specific for hepatitis B virus (HBV) core peptides are inhibitory to other HBV core-specific CD4+ T cells in vitro

A strong and transient hepatitis B virus core (HBc)-specific CD4+ T-cell response has been shown to be associated with viral elimination in acute self-limited hepatitis B but to be absent in chronic hepatitis B. So far, little is known about immunological mechanisms involved in the regulation of the HBc-specific CD4+ T-cell response. We studied 28 patients with acute hepatitis B, and frequently a sudden decrease in the HBc-specific CD4+ T-cell response was found between 4 and 8 weeks after disease onset. Thirty-two CD4+ T-cell clones specific for amino acids 50 to 69, 81 to 105, 117 to 131, or 141 to 165 of HBc were isolated from a patient shortly before the peripheral blood mononuclear cell response to most HBc-derived peptides abruptly disappeared. TH1 clones, but not TH0 clones, could be anergized in vitro by stimulation with specific peptides even in the presence of costimulatory cells. Moreover, when anergic cells were mixed with responsive cells, the proliferation of HBc-specific TH1 or TH0 clones was inhibited antigen specifically by anergic cells. The unusual susceptibility of HBc-specific TH1 clones to anergy induction in vitro as well as their potential to inhibit other HBc-specific TH1 and TH0 clones suggests that anergy induction may be involved in the downregulation of the virus-specific immune response during acute hepatitis B in vivo.