Proliferation of peripheral lymphocytes to interleukin-2 and interleukin-4 after marrow transplantation.

Defects in the interleukin-2 (IL-2)-mediated T-lymphocyte activation/proliferation pathway have been implicated as contributing to the compromised immune function observed in patients following bone marrow transplantation (BMT). Since interleukin-4 (IL-4) is also involved in T-lymphocyte function, we have examined whether phytohemagglutinin (PHA)- or anti-CD3 (OKT3)-activated lymphocytes obtained from patients after allogeneic or autologous BMT are capable of proliferating in response to human recombinant IL-4, and compared these results to those obtained using human recombinant IL-2. Peripheral blood lymphocytes from marrow graft recipients were initially cultured for 3 days in the presence of PHA or OKT3. Such mitogen-activated lymphocytes exhibited little or no proliferation (as assessed by incorporation of [3H]-thymidine) following culture for an additional 3 days in the presence of IL-4 or IL-2. Results were similar for lymphocytes obtained from patients early (less than 4 months) after marrow grafting and those obtained from long-term marrow graft recipients with chronic graft-vs-host disease at the time of testing. In contrast, lymphocytes obtained from healthy individuals proliferated in response to IL-4, as well as to IL-2, following initial activation with PHA or OKT3. Immunofluorescence analysis showed that in normals equal numbers of CD4 and CD8 cells proliferated after stimulation with anti-CD3 antibody and IL-2. However, in BMT patients there was a predominant proliferation of CD8 cells using the same stimulator. These results indicate that defects in the IL-4-mediated T-lymphocyte activation/proliferation pathway may also contribute to the immunodeficiency observed following BMT.     

Expression of interleukin-2 receptor on blood lymphocytes stimulated with allogeneic lymphocytes or autologous tumor cells

Summary The kinetics of interleukin-2 receptor (IL-2R) expression and the [³H]dT incorporation of blood lymphocytes after the first and the second stimulation with allogeneic leukocytes (primary and secondary MLC) or with the autologous tumor cells (primary and secondary MLTC) were compared. The expression of IL-2R paralleled the induction of DNA synthesis. The proportion of IL-2R⁺ cells of the unprimed donors peaked earlier in the secondary MLC as compared to the primary MLC (on days 3 and 5 respectively). In MLC of alloimmunized healthy individuals and in the MLTC of cancer patients the highest proportions of IL-2R⁺ cells were detected between days 2 and 3 after both the first and second stimulations. Thus the first in vitro stimulation in the MLTC showed similar kinetics to those of the secondary MLC of unprimed individuals and to the primary MLC response of the allo-immunized individuals. The findings in the MLTC substantiate the hypothesis that cancer patients can be sensitized to their own tumors. The kinetics of the appearance of the IL-2R together with the characteristics of the IL-2-propagated cultures provide useful information for the strategy of expansion of auto-tumor reactive lymphocyte populations.     

Suppression of interleukin-2 production by human concanavalin A-induced suppressor cells

When PHA-activated normal responder cells (R cells) were cocultured with mononuclear cells (MN cells) which had been preincubated for 48 hr in medium alone (C cells) an enhanced proliferative response was observed. This enhancement was only obtained when the R cells were cultured with allogeneic C cells or when PHA was in the cocultures for the entire culture period. This effect was due to greater production of interleukin 2 (IL-2) by irradiated C cells in the presence of allogeneic or mitogenic stimulation. Con A-treated mononuclear cells (S cells) cultured with PHA-activated allogeneic or autologous responder cells showed reduced [3H]thymidine incorporation and IL-2 production as compared to activated R cells alone. Glutaraldehyde-treated S cells (which retained the ability to absorb IL-2) did not affect the proliferative response or IL-2 production by the R cells, indicating that passive absorption of IL-2 was not entirely responsible for suppression induced by S cells. S cells, pretreated with IL-2, still inhibited R-cell activity. These results show that Con A-treated MN cells suppressed or prevented [3H]thymidine incorporation by actively inhibiting IL-2 production.     

Expression of interleukin-4 in apoptotic cells: stimulation of the type-2 cytokine by different toxins in human peripheral blood mononuclear and tumor cells

BACKGROUND: Immunological reactivity is regulated by T-cell populations (type-1 and type-2 cells) via cytokine secretion, but their influence on apoptosis remains unclear. METHODS: Intracellular expression of type-1 (interferon [IFN]-gamma) and type-2 (interleukin [IL]-4) cytokines and apoptosis-related molecules (Apo2. 7, Bcl-2 protein) was studied by flow cytometry in human peripheral blood mononuclear cells (PBMC), myeloma (U-266), monocytic (THP-1), and T-leukemia cells (MOLT-4) in response to toxins, which act on different intracellular targets (actinomycin D, cycloheximide, the mistletoe lectins [ML]-1 and ML-3, brefeldin A, staurosporine). RESULTS: The apoptosis-inducing toxins stimulated intracellular IL-4 expression mainly in PBMC with high expression of the mitochondrial apoptosis marker, Apo2.7, but with decreased level of the anti-apoptotic Bcl-2 protein. Up-regulation of IL-4 coincided with a significant down-regulation of IFN-gamma in CD4(+) and CD8(+) cells. The inhibitor of oxidative phosphorylation, oligomycin, and the caspase inhibitor, z-VAD-fmk, abolished IL-4 expression and DNA fragmentation in the PBMC. Also in the myeloma, monocytic, and T-leukemia cells, IL-4 was mainly observed in the Apo2.7(+) apoptotic cells in response to the toxins. CONCLUSIONS: We suggest that the different apoptotic toxins activate a common pathway in which IL-4 production plays a yet unknown intracellular role further downstream during apoptosis.     

Role of interleukin-4 and prostaglandin E2 in Leishmania amazonensis infection of BALB/c mice

The role of cytokines in Leishmania amazonensis experimental infection has not been as well studied as in Leishmania major infection model. Here we investigated the role of interleukin (IL)-4 and PGE(2) in L. amazonensis infection of susceptible BALB/c mice. IL-4 deficient (-/-) or wild-type (+/+) BALB/c mice were infected with different inocula of L. amazonensis. Two weeks after infection with 5x10(6) promastigotes/footpad, the production of interferon (IFN)-gamma upon L. amazonensis antigen stimulation was significantly higher in lymph node cell cultures of IL-4-/- mice than in IL-4+/+ mice. The levels of anti-leishmania IgG2a antibodies were also significantly higher in serum from IL-4-/- mice. In contrast, the levels of IgG1 antibodies were increased in IL-4+/+ mice and almost undetectable in IL-4-/- mice. Despite the increased Th1 response, lesions of IL-4-/- BALB/c mice progressed similarly to those of IL-4+/+ mice upon infection with the 5x10(6) inoculum. However, IL-4-/- mice developed smaller lesions upon infection with 10(5), 10(4) or 10(3) parasites than IL-4+/+ mice. The resistance of IL-4-/- correlated with higher Th1 response, compared to IL-4+/+ upon infection with 10(4)L. amazonensis. IL-4+/+ mice treated with indomethacin, an inhibitor of PGE(2) synthesis, during the first 3weeks of infection developed smaller lesions and lower parasitic load when compared to the control group. The lesions of indomethacin-treated groups contained mostly macrophages without vacuoles and small or absent necrotic areas. These results indicate that IL-4 and PGE(2) are susceptibility factors to L. amazonensis infection.     

A Comparison of Colorimetric and DNA Quantification Assays for the Assessment of Meniscal Fibrochondrocyte Proliferation in Microcarrier Culture

We have developed and refined a rapid, reliable method for the evaluation of attachment and proliferation of ovine meniscal chondrocytes in microcarrier culture. Assays measuring both mitochondrial activity, using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] and MTS [3-(4,5-dimethylthiazol-2-yl)5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium], and DNA synthesis with a PicoGreen assay were compared. The MTT assay was the most sensitive at lower cell concentrations and enabled accurate assessment of cell proliferation over 14 day culture.     

Regulation of fibroblast cyclooxygenase synthesis by interleukin-1

We have prepared polyclonal antiserum against sheep seminal vesicle prostaglandin H synthase (also termed cyclooxygenase) which cross-reacted with human cyclooxygenase, thereby enabling us to directly determine the synthetic rate of cyclooxygenase protein and its modulation by the monokine interleukin-1 (IL-1). Cultured human dermal fibroblast cells were labeled with [35S]methionine, and the membrane-bound cyclooxygenase was solubilized and immunoprecipitated 35S-labeled fibroblast cyclooxygenase migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular size of approximately 73,000 daltons, similar to that of native sheep cyclooxygenase and of cyclooxygenase covalently labeled by [3H]aspirin, i.e. [3H]acetylcyclooxygenase. Additional validation of the immunoprecipitated 35S-labeled cyclooxygenase band indicated that it was specifically displaced by unlabeled sheep cyclooxygenase. N-terminal amino acid radiosequence analysis of [3H]proline-labeled cyclooxygenase revealed [3H]proline residues in positions 3, 6, and 8, consistent with the previously reported N-terminal sequence of sheep cyclooxygenase. Endoglycosidase H treatment of 35S-labeled fibroblast cyclooxygenase caused a decline in apparent molecular size (due to removal of mannose residues) which was similar to that seen with the native sheep cyclooxygenase. [35S]Methionine pulse-chase experiments indicated a half-life of 1 h for fibroblast cyclooxygenase. The monokine interleukin-1 stimulated fibroblast cyclooxygenase synthesis in a time- and dose-dependent fashion; as little as 0.03 unit/ml of IL-1 produced significant stimulation of 35S-labeled cyclooxygenase synthesis. Maximum stimulation was 3-10-fold after preincubation of the cells with 0.3 unit/ml of IL-1 for 12-16 h. IL-1 treatment of cells yielded parallel dose-response curves for stimulation of prostaglandin E2 formation, increased cellular cyclooxygenase activity, and increased synthetic rate of newly formed cyclooxygenase, suggesting that the IL-1 effect is mediated mainly, if not solely, via induction of cyclooxygenase synthesis.     

Distinct biological activities of recombinant forms of human interleukin-2 in vivo

 The biological activity of all recombinant forms of interleukin-2 (IL-2) is based upon an in vitro lymphocyte proliferation assay and measured in international units (IU). Numerous in vitro investigations have suggested that there may be different cellular effects of recombinant human IL-2 retaining the natural sequence (nIL-2) as compared to another recombinant form containing a serine substitution at amino acid position 125 ([Ser]IL-2). In the present study we investigated whether nIL-2 and [Ser]IL-2 cause similar patterns of systemic toxicities. C57BL/6 mice were treated with identical doses of either nIL-2 or [Ser]IL-2, as measured in IU, for 3 days and had blood and tissues removed for analysis of lymphocyte activation and organ dysfunction. The administration of nIL-2 had considerably greater effects on lymphocyte activation than did [Ser]IL-2, causing much greater up-regulation of the α subunit of the IL-2 receptor and the adhesion molecule lymphocyte function-associated antigen-1. Furthermore, nIL-2 induced more organ edema than did [Ser]IL-2 and caused hepatocellular injury, which was absent in mice treated with [Ser]IL-2. These data demonstrate that equivalent doses, measured in IU, of nIL-2 and [Ser]IL-2 have profoundly different effects on the induction of organ toxicity, suggesting that the IU standard may not be appropriate for the measurement of many in vivo biological activities. Received: 30 August 1996 / Accepted: 8 November 1996     

IL-4 Suppresses the Responses to TLR7 and TLR9 Stimulation and Increases the Permissiveness to Retroviral Infection of Murine Conventional Dendritic Cells

Th2-inducing pathological conditions such as parasitic diseases increase susceptibility to viral infections through yet unclear mechanisms. We have previously reported that IL-4, a pivotal Th2 cytokine, suppresses the response of murine bone-marrow-derived conventional dendritic cells (cDCs) and splenic DCs to Type I interferons (IFNs). Here, we analyzed cDC responses to TLR7 and TLR9 ligands, R848 and CpGs, respectively. We found that IL-4 suppressed the gene expression of IFNβ and IFN-responsive genes (IRGs) upon TLR7 and TLR9 stimulation. IL-4 also inhibited IFN-dependent MHC Class I expression and amplification of IFN signaling pathways triggered upon TLR stimulation, as indicated by the suppression of IRF7 and STAT2. Moreover, IL-4 suppressed TLR7- and TLR9-induced cDC production of pro-inflammatory cytokines such as TNFα, IL-12p70 and IL-6 by inhibiting IFN-dependent and NFκB-dependent responses. IL-4 similarly suppressed TLR responses in splenic DCs. IL-4 inhibition of IRGs and pro-inflammatory cytokine production upon TLR7 and TLR9 stimulation was STAT6-dependent, since DCs from STAT6-KO mice were resistant to the IL-4 suppression. Analysis of SOCS molecules (SOCS1, −2 and −3) showed that IL-4 induces SOCS1 and SOCS2 in a STAT6 dependent manner and suggest that IL-4 suppression could be mediated by SOCS molecules, in particular SOCS2. IL-4 also decreased the IFN response and increased permissiveness to viral infection of cDCs exposed to a HIV-based lentivirus. Our results indicate that IL-4 modulates and counteracts pro-inflammatory stimulation induced by TLR7 and TLR9 and it may negatively affect responses against viruses and intracellular parasites.     

High interleukin-4 expression and interleukin-4 gene polymorphisms are associated with susceptibility to human paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is caused by dimorphic fungi from theParacoccidioides brasiliensis complex. Previous studies have demonstrated that the severity of disease is associated with a T-helper 2 immune response characterised by high interleukin (IL)-4 production. In the present study we analysed two polymorphisms in the IL-4 gene (-590 C/T and intron-3 microsatellite) in 76 patients with PCM and 73 control subjects from an endemic area. The production of IL-4 by peripheral blood mononuclear cells after antigen or phytohaemagglutinin stimulation was determined by ELISA. A significant correlation was observed between the RP2/RP2 intron-3 genotype and infection with Paracoccidioides sp. (p = 0.011), whereas the RP1/RP1 genotype was correlated with resistance. No significant correlation was observed for the IL-4 promoter polymorphism. Furthermore, the low IL-4 expression observed in the control group compared with patients was associated with the RP1/RP1 genotype. These results suggest that IL-4polymorphisms might be associated with the ability of the host to control Paracoccidioides sp. infection. The relevance of this polymorphism is supported by the observation that patients with disease produce high levels of IL-4 following mitogen or antigen stimulation. The IL-4 gene is located in the cytokine cluster region of chromosome 5 where other polymorphisms have also been described.     

Th2-type immune response observed in healthy individuals to sonicate antigen prepared from the most prevalent Mycobacterium tuberculosis strain with single copy of IS6110

Different Mycobacterium tuberculosis strains operate different immune evasion strategies for their survival in the host. This mainly depends on the virulence of the strain and the host immune responses. The most virulent strains are actively involved in the transmission, widely spread in the community and induce differential immune responses. We evaluated the immune response of a sonicate antigen prepared from one predominant strain (S7) from M. tuberculosis harbouring a single copy of IS6110. Significant lymphoproliferative response against purified protein derivative from tubercle bacillus (PPD) and H37Rv antigens was observed in PPD positive normal individuals and tuberculosis patients. Interferon-gamma (IFN-gamma) levels against these antigens were significantly increased in normal individuals but not in tuberculosis patients. The antigen S7 showed marginal T-cell proliferation but did not induce IFN-gamma secretion in both groups. Conversely, it induced significantly high levels of cytokine interleukin 4 (IL-4) in normal individuals. The macrophage cytokines, IL-12 and tumour necrosis factor alpha (TNF-alpha), did not show S7 antigen specific stimulation. The intracellular cytokine further confirmed an increase in IL-4(+)/CD4+ T-cells and a decrease in IFN-gamma(+)/CD4+ T-cells upon stimulation. The antibody response showed an increase in IgG and IgA levels against this antigen in normal individuals. These observations suggest that antigen S7 modulates the immune response towards T helper cell type 2 by suppressing T helper cell type 1 protective immune response in PPD positive normal individuals. We speculate that some components of this sonicate antigen are associated with immunosuppressive response.     

Interleukin-1 stimulation of arachidonic acid release from human synovial fibroblasts; blockade by inhibitors of protein kinases and protein synthesis

Addition of IL-1 (interleukin-1) to human synovial fibroblasts radiolabelled with [3H]arachidonic acid caused a linear dose-dependent increase in arachidonic acid release and a transient rise in labelled diacylglycerol. Protein kinase C activators PMA 4-phorbol 12-myristate 13-acetate and DiC8 (1,2-dioctanoyl-sn-glycerol) also increased arachidonic acid release, but the time course observed with PMA was different from that of IL-1. When cultures were treated with PMA for 16-24 h to down regulate protein kinase C, the ability of IL-1 to increase arachidonic acid release persisted to the same extent as in nontreated cultures. In contrast, PMA pretreatment prevented the eight-fold stimulation of arachidonic acid release in response to PMA observed in cultures not previously exposed to PMA. To examine the role of other kinases in IL-1 stimulated arachidonic acid release, cultures were treated with H-7 (1-(5-isoquinolinesulphonyl)-2-methylpiperazine dichloride), H-8 (N-[2-(methylamino) ethyl]-5-isoquinolinesulphonamide dichloride), HA1004 (N-(2-guanidoinoethyl)-5-isoquinolinesulphonamide hydrochloride), and staurosporine. IL-1 stimulation of arachidonic acid release was blocked by H-7, H-8 and staurosporine. H-7 was a more potent inhibitor than H-8, suggesting that cAMP dependent kinase did not mediate IL-1 action. Addition of H-7 at various times following IL-1 decreased IL-1 stimulated arachidonic acid release, suggesting that continued protein kinase activity was necessary for IL-1 action. Cycloheximide and actinomycin D inhibited the stimulation of arachidonic acid release by IL-1, PMA or DiC8. The addition of cycloheximide or actinomycin D 15-45 min after IL-1 also inhibited IL-1 stimulated arachidonic acid release, indicating that continued protein synthesis was required for IL-1 action. These results suggest that IL-1 stimulation of acylhydrolyase activity in human synovial cells occurs by a mechanism requiring continued protein synthesis and protein kinase activity and that neither protein kinase C nor cAMP dependent protein kinase is involved.     

Bombesin and its analogues inhibit interleukin-2-induced proliferation of CTLL-2 cells

Specifically interleukin-2 (IL-2)-dependent CTLL-2 cells were incubated in short term culture in the presence of IL-2 together with bombesin and two analogues, [Lys3]bombesin and [Tyr4]bombesin in different concentrations. Cell proliferation, determined by [3H]thymidine incorporation was significantly inhibited by 35.6 +/- 5%, 39.0 +/- 5.6% and 57.0 +/- 11% (mean +/- S.E.M. of 3 independent experiments). A typically U-shaped dose-response relationship was observed, showing a maximum effect between 10(-12) and 10(-10) M. Our data support the hypothesis that this effect is mediated by a specific receptor for bombesin and closely related peptides on CTLL-2 cells. As IL-2 plays a critical role in the clonal expansion of activated lymphocytes, antagonism of the effect of IL-2 is of high biological significance.     

IL-10 and toll-like receptor-4 polymorphisms and the in vivo and ex vivo response to endotoxin

To determine to what extent lipopolysaccharide-induced IL-10 production capacity is determined by polymorphisms in toll-like receptor-4 (TLR4) and the IL-10 promoter region, we measured in vivo IL-10 and TNF-alpha production in patients undergoing elective cardiopulmonary bypass surgery, a major surgical trauma associated with ischemia-reperfusion injury that triggers an endotoxemia and profound inflammatory response in most patients. Ex vivo the IL-10 and TNF-alpha production was measured in a whole blood stimulation assay, using 3 LPS concentrations. Positive correlations were found between TNF-alpha and IL-10 production ex vivo, upon stimulation with each of the LPS concentrations. Also, the estimated TNF-alpha and IL-10 EC50, and TNF-alpha(max) and IL-10max were positively correlated (r = 0.203; p = 0.023 and r = 0.287; p = 0.001, respectively), indicating that these parameters describing LPS sensitivity and maximal production capacity, respectively, can be estimated by measuring either TNF-alpha or IL-10. Interleukin-10 concentrations in patients experiencing endotoxemia in vivo negatively correlated with the IL-10 levels produced upon stimulation with 1000 ng/mL LPS as well as the estimated IL-10max ex vivo. In vivo, a positive correlation between the TNF-alpha concentration at time-point 2 and the IL-10 concentration at time-point 3 was found, consistent with an important contribution of the magnitude of TNF-alpha release upon the subsequent IL-10 production. Carriers of the IL-10 promoter -1330G, -1082A, -819T, -592A (GATA) haplotype had lower IL-10 production ex vivo upon stimulation with 10 and 100 ng/mL LPS and higher EC50 values (the estimated LPS concentration at which 50% of the maximal IL-10 response is reached) as compared to carriers of the other haplotypes combined, indicating decreased LPS sensitivity ex vivo. These individuals did not differ from the others in interleukin-10 production capacity upon stimulation with a high LPS concentration (i.e., 1000 ng/mL) and the estimated IL-10(max) values, were similar, indicating unimpaired maximal IL-10 production capacity ex vivo. Carriers of the IL-10 promoter AGCC haplotype had lower EC50 values as compared to carriers of the other haplotypes combined, indicating increased LPS sensitivity ex vivo. In accordance with this finding, carriers of the AGCC haplotype had higher circulating IL-10 levels in vivo. The common TLR4 polymorphisms (Asp299Gly and Thr399Ile) were associated with slightly higher IL-10 production capacity ex vivo and in vivo, however, this was not statistically significant. Our results indicate that polymorphisms in the proximal IL-10 promoter region are associated with in vivo and ex vivo LPS sensitivity. The contribution to the inter-individual variation, however, is limited since the variation between individuals in LPS sensitivity and IL-10 production capacity can only partly be attributed to these IL-10 promoter polymorphisms.     

Concurrent production of interleukin-2, interleukin-10, and gamma interferon in the regional lymph nodes of mice with influenza pneumonia.

Cytokine production has been assessed at the single-cell level (ELISPOT assay) for freshly isolated mediastinal lymph node cells from C57BL/6 mice with primary, nonfatal influenza pneumonia. The mediastinal lymph node populations were also secondarily stimulated in vitro, and culture supernatants were assayed by enzyme-linked immunosorbent assay. Both approaches showed minimal evidence of protein secretion for interleukin-4 (IL-4), IL-5, and tumor necrosis factor, while IL-2, IL-10, and gamma interferon (IFN-gamma) were prominent throughout the response. The numbers of IL-2- and IFN-gamma-producing cells were maximal at 7 days after infection, while the total counts for cells secreting IL-10 were fairly constant from day 3 to 7. The cultures that were stimulated with virus in vitro showed in inverse relationship between IL-10 and IFN-gamma production, with IL-10 peaking on day 3 and IFN-gamma peaking on day 7. Lymphocytes secreting IL-2, IL-10, and/or IFN-gamma were present in CD4+ and CD8+ populations separated by fluorescence-activated cell sorting, although the CD8+ T cells produced less cytokine and were at a relatively lower frequency. Addition of recombinant IL-10 to the virus-stimulated cultures decreased the amount of IFN-gamma that could be detected, while incorporation of a monoclonal antibody to IL-10 had the opposite effect. A neutralization experiment also indicated that IL-2 was the principal mediator of lymphocyte proliferation. These experiments thus show that the developing T-cell response in the regional lymph nodes of mice with influenza cannot be rigidly categorized on the basis of a TH1 or TH2 phenotype and suggest possible regulatory mechanisms.     

Glutamine decreases interleukin-8 and interleukin-6 but not nitric oxide and prostaglandins e(2) production by human gut in-vitro

BACKGROUND: Glutamine modulates cytokine production in various tissues but its effects on the production of other inflammatory mediators such as eicosanoids and nitric oxide have not been investigated in human gut. AIM: To evaluate the influence of glutamine on interleukin (IL)-8, IL-6, nitric oxide and prostaglandin E(2) production by human gut. METHODS: Ten fasted volunteers received either enteral glutamine or isonitrogenous amino acids over 6 h in a cross-over design. Series of duodenal biopsies were frozen or cultured for 24 h with 0.5 or 5 mM of glutamine or amino acids. IL-6, IL-8 and PGE(2) were measured in culture media by ELISA and nitrites by Griess assay. mRNA levels for IL-6, IL-8, Cyclooxygenase-2 and NO synthase-2 were assessed in biopsies by RT-PCR. Results in percent, (median [range]) were compared by Wilcoxon test. RESULTS: Glutamine decreased IL-8 and IL-6 in-vitro production: 63 [2-173] vs 100 [19-177] and 37 [5-489] vs 100 [33-431], both P<0.05. IL-8 mRNA level also decreased in biopsies cultured with 5 mM glutamine: 26 [13-142] vs 92 [34-215], P<0.05. Nitrites and PGE(2) concentrations were not significantly affected by glutamine. CONCLUSION: Glutamine has a specific inhibitory effect on pro-inflammatory cytokine production in the gut and may contribution to the modulation of intestinal inflammation.     

Differential effects of interleukin-2 and interleukin-4 on protein tyrosine phosphorylation in factor-dependent murine T cells

Interleukin-2 (IL-2) is a requisite factor for growth and proliferation of IL-2-dependent T cells. At present, the mechanism by which the high-affinity IL-2-IL-2 receptor interaction transmits a mitogenic signal to the cellular interior remains unclear. In this report we have used three murine T cell clones to demonstrate that IL-2 stimulates rapid tyrosine phosphorylation of several proteins. Two of these clones, CTLL-2 and CT6, exhibit a cytotoxic T cell phenotype, while the third, HT-2, was derived from a helper T cell line. All three T cell clones proliferated in response to IL-2 stimulation, but HT-2 cells also proliferated in response to interleukin-4 (IL-4). We comparatively examined the effects of IL-2 and IL-4 on protein tyrosine phosphorylation in these cells by immunoaffinity purification of phosphotyrosyl substrates with an anti-phosphotyrosine monoclonal antibody. Stimulation with concentrations of IL-2 resulting in maximal (10-30 U/ml) or sub-maximal (1-5 U/ml) proliferation caused the rapid tyrosine phosphorylation of 97 and 57 kDa proteins in all three cell lines. The 97 kDa protein was localized in the cytosol, while the 57 kDa protein was detected in both cytosolic and crude membrane fractions. IL-2-dependent tyrosine phosphorylation of an 86 kDa cytosolic protein was observed only in CT6 cells. Tyrosine phosphorylation of 22, 23 and 200 kDa proteins was also observed, but only in the cytotoxic T cell clones. Phosphoamino acid analyses revealed that the 97, 86 and 57 kDa proteins contained phosphotyrosine and phosphoserine residues. Concentrations of IL-2 below the threshold concentration for induction of a proliferative response correspondingly failed to stimulate protein tyrosine phosphorylation. In contrast, growth stimulation of HT-2 cells by IL-4 was not preceded by early changes in protein tyrosine phosphorylation, suggesting that protein tyrosine phosphorylation may not be essential for the induction of IL-4-dependent cell-cycle progression. These results demonstrate that high-affinity IL-2 receptors are coupled to tyrosine kinase activity(s) in T cells. However, the failure of IL-4 to stimulate protein tyrosine phosphorylation in the same cells indicates that enhanced protein tyrosine phosphorylation may not be requisite for growth factor-dependent T cell proliferation.     

Functional regions of the mouse interleukin-10 receptor cytoplasmic domain.

The functions of wild-type and mutant mouse interleukin-10 receptors (mIL-10R) expressed in murine Ba/F3 cells were studied. As observed previously, IL-10 stimulates proliferation of IL-10R-expressing Ba/F3 cells. Accumulation of viable cells in the proliferation assay is to a significant extent balanced by concomitant cell death. Moreover, growth in IL-10 also induces a previously unrecognized response, differentiation of the cells, as evidenced both by formation of large clusters of cells in cultures with IL-10 and by induction or enhancement of expression of several cell surface antigens, including CD32/16, CD2, LECAM-1 (v-selectin), and heat-stable antigen. Two distinct functional regions near the C terminus of the mIL-10R cytoplasmic domain which mediate proliferation were identified; one of these regions also mediates the differentiation response. A third region proximal to the transmembrane domain was identified; removal of this region renders the cell 10- to 100-fold more sensitive to IL-10 in the proliferation assay. In cells expressing both wild-type and mutant IL-10R, stimulation with IL-10 leads to tyrosine phosphorylation of the kinases JAK1 and TYK2 but not JAK2 or JAK3 under the conditions tested.     

Monocyte-independent interleukin-2 production and proliferation of human T cells in response to murine hybridomas expressing the OKT3 monoclonal antibody: interleukin-1 is not required for T-cell proliferation

We report a new, monocyte-independent system for the induction of activation and proliferation of human T cells in response to murine hybridomas expressing the OKT3 monoclonal antibody (OKT3 hybridomas). Incubation of nylon-wool-nonadherent (NA) lymphocytes or purified T cells with OKT3 hybridomas resulted in interleukin-2 (IL-2) production, expression of IL-2 receptor, modulation of the CD3 antigen, and proliferation. In contrast, murine hybridomas (OKT4, OKT8, anti-HLA-DR, and others) expressing monoclonal antibodies (mAb) other than OKT3 did not induce T-cell activation and proliferation. T cells did not respond to OKT3 mAb alone. OKT3 hybridomas alone did not produce interleukin-1 (IL-1) or other soluble factors that might be involved in the induction of IL-2 production by T cells, and they did not contain membrane-bound IL-1. In addition, IL-1 activity was not detected in cultures of NA-lymphocytes and OKT3 hybridomas, clearly demonstrating that IL-1 was not required, at least in this system, for T-cell activation and proliferation. Direct cell-cell contact between T cells and OKT3 hybridomas was required for IL-2 production. Thirty to fifty percent of T cells formed conjugates with the OKT3 hybridomas but not with the OKT4 or OKT8 hybridomas. Both conjugate formation and IL-2 production were significantly inhibited by the OKT3 mAb and by the anti-LFA-1 mAb. The cells responsible for IL-2 production were found to be of the T3+ T4+ T8- Leu 7- Leu 11- phenotype. IL-2 activity produced by NA-lymphocytes in response to OKT3 hybridomas became detectable as early as 1 hr and reached a maximum by 8 hr, preceding IL-2 receptor expression, modulation of the CD3 antigen, and [3H]thymidine incorporation of T cells. T cells produced higher concentrations of IL-2 in response to OKT3 hybridomas than in response to equal numbers of monocytes and OKT3 mAb. Addition of monocytes to cultures of T cells and OKT3 hybridomas resulted in suppression of IL-2 production in a concentration-dependent manner, suggesting that monocytes regulate the levels of IL-2 production. This monocyte-independent system may be useful for further dissection of T-cell activation and proliferation and its regulation by monocytes.     

Interleukin 2 rapidly stimulates synthesis and breakdown of polyphosphoinositides in interleukin 2-dependent, murine T-cell lines

Several T-cell functions are controlled by the regulatory peptide interleukin 2 (IL-2). Binding of IL-2 with specific receptors has been well documented, but the molecular mechanism by which IL-2/IL-2 receptor interaction is transduced is not known. We have found that treatment of IL-2-dependent T-cell lines with IL-2 is followed by a rapid stimulation of inositol phospholipid metabolism, as determined by isotopic methodology employing myo-[1,2-3H]inositol. Increased incorporation of the metabolic precursor into phosphatidylinositol and phosphatidylinositol 4-monophosphate, together with the appearance of radiolabeled phosphatidylinositol 4,5-bisphosphate, occurred within minutes of treatment with IL-2 of factor-dependent CT6 cells. Analysis of labeled water-soluble compounds from prelabeled cells indicated a rapid (within 1 min) stimulation of inositol phospholipid hydrolysis following IL-2 treatment. Increased recovery of [3H] inositol phosphates and appearance of [3H]inositol trisphosphate were observed after treatment with IL-2 of CT6 cells, as well as of a second IL-2-dependent cell line, CTB6. These findings suggests that inositol phospholipid-derived metabolites (i.e. diacylglycerol and inositol trisphosphate) may be part of the mechanism by which certain IL-2 signals are transduced.