Detection of and discrimination between total and free human interleukin-4 and free soluble interleukin-4 receptor by ELISA

Type I IL-4Rs selectively activate IRS-2 to induce target gene expression in macrophages

Although interleukin-4 (IL-4) and IL-13 participate in allergic inflammation and share a receptor subunit (IL-4Ralpha), they have different functions. We compared cells expressing type I and II IL-4Rs with cells expressing only type II receptors for their responsiveness to these cytokines. IL-4 induced highly efficient, gammaC-dependent tyrosine phosphorylation of insulin receptor substrate 2 (IRS-2), whereas IL-13 was less effective, even when phosphorylation of signal transducer and activator of transcription 6 (STAT6) was maximal. Only type I receptor, gammaC-dependent signaling induced efficient association of IRS-2 with the p85 subunit of phosphoinositide 3-kinase or the adaptor protein growth factor receptor-bound protein 2. In addition, IL-4 signaling through type I IL-4Rs induced more robust expression of a subset of genes associated with alternatively activated macrophages than did IL-13. Thus, IL-4 activates signaling pathways through type I IL-4Rs qualitatively differently from IL-13, which cooperate to induce optimal gene expression.

Glucosamine abrogates the acute phase of experimental autoimmune encephalomyelitis by induction of Th2 response

Glucosamine, a natural glucose derivative and an essential component of glycoproteins and proteoglycans, has been safely used to relieve osteoarthritis in humans. Recent studies have shown that glucosamine also possesses immunosuppressive properties and is effective in prolonging graft survival in mice. Whether this reagent is effective in human multiple sclerosis (MS), an inflammatory demyelination in the CNS, is not known. We thus investigated the therapeutic effect of glucosamine on experimental autoimmune encephalomyelitis (EAE), an animal model of MS. We demonstrated that oral, i.p., or i.v. administration of glucosamine significantly suppressed acute EAE, with reduced CNS inflammation and demyelination. A significant, albeit not strong, blockade of Th1 response and an up-regulation of Th2 cytokines (IL-5 and IL-10) are observed in the splenocytes of glucosamine-treated mice. Glucosamine also regulates IL-5 and IL-10 in vitro. As glucosamine is able to effectively suppress acute EAE, has low or absent toxicity, and has been safely used in humans orally, our study suggests a potential use for this drug alone or in combination with other disease-modifying immunotherapies to enhance their efficacy and reduce their doses in MS and possibly other autoimmune disorders. Furthermore, because glucosamine functions not simply as an immunosuppressant, but as a mild immunomodulator, administration of glucosamine provides a novel immunoregulatory approach for autoimmune disorders.

CD45 isoform expression is associated with different susceptibilities of human naive and effector CD4+ T cells to respond to IL-4

Interleukin-4 (IL-4) is the major factor promoting the development of T helper type 2 (Th2) cells from naive precursor T cells. Minute amounts of IL-4 produced by naive T cells seem to be sufficient; however, the molecular mechanisms explaining this efficient utilization of IL-4 are not yet known. Here, we show that human CD4+ CD45RA+ naive T cells, in contrast to CD4+ CD45R0+ effector T cells, show responsiveness to endogenous as well as exogenous IL-4 to proliferate and differentiate towards Th2 cells in vitro. Despite production levels of IL-4 below conventional detection limits, CD45RA+ T cell-derived IL-4 could clearly activate STAT6. Although the expression levels of IL-4R and STAT6 were not different between naive and effector T cells, only naive T cells responded to IL-4 in a STAT6-dependent reporter gene assay. Transfecting a trans-dominant negative form of STAT6 abrogated IL-4-induced proliferation in CD45RA+ cells. A significantly higher protein tyrosine phosphatase (PTPase) activity was detected in CD45R0+ T cells as compared to CD45RA+ T cells. Cross-linking CD45 potently reduced PTPase activity in CD45R0+ T cells and restored their ability to proliferate in response to IL-4. Thus, CD45 PTPase activity contributes to the susceptibility of naive and memory T cells to respond to IL-4.

Deficient translocation of c-Rel is associated with impaired Th1 cytokine production in T cells from atopic dermatitis patients

Decreased production of T helper type 1 (Th1) cytokines, such as interferon-gamma (IFN-gamma) or interleukin-2 (IL-2), is a hallmark of atopic diseases. While accessory signals from antigen-presenting cells may be missing, T cells themselves may be suppressed in their ability to produce substantial amounts of Th1 cytokines. We show, in this study, that T cell receptor (TCR)-activated T cells from atopic dermatitis (AD) patients proliferate less than control T cells and produce lower amounts of IFN-gamma and IL-2, but comparable amounts of IL-4. Because mice lacking the nuclear factor kappa B (NF-kappaB) transcription factors - p65 or c-Rel - show reduced Th1, but undisturbed Th2 responses, we investigated the role of c-Rel and p65 for Th1 cytokine production in T cells from healthy and severe AD patients. TCR-activated primary T cells from healthy donors treated with c-Rel antisense oligonucleotides produced lower levels of IL-2 and IFN-gamma and proliferated less efficiently than the corresponding control T cells. Moreover, transfection of primary T cells with c-Rel or p65 enhanced proliferation and production of IL-2 and IFN-gamma. Nuclear extracts of activated primary T cells from AD donors bound weakly to NF-kappaB-specific oligonucleotides, compared to extracts from healthy control T cells. Western blotting studies revealed that nuclear, but not cytosolic, extracts from T cells of AD patients lacked significant amounts of c-Rel and p65. T cell clones derived from AD patients failed to sufficiently translocate c-Rel and p65 into the nucleus following activation. Thus, impaired nuclear translocation of c-Rel and p65 may determine an impaired Th1 cytokine response in AD.

Naïve CD4+ T cells from patients with atopic dermatitis show an aberrant maturation towards IL-4-producing skin-homing CLA+ cells

Overproduction of interleukin-4 (IL-4) has been reported in lesional and in peripheral T cells from patients with atopic dermatitis (AD). It is not clear whether the development of IL-4-producing T helper type 2 (Th2) cells from naïve precursors is an intrinsic phenomenon of T cells or whether other, extrinsic factors play a significant role. To analyze these alternatives, we investigated the IL-4 production of effector T cells generated in vitro from highly purified CD4+ CD45RA+ naïve T cells in the absence of signals derived from antigen-presenting cells. Effector T cells generated from naïve precursors from both AD and healthy donors produced comparable amounts of IL-4 after restimulation. Priming in the presence of exogenous IL-4 enhanced the production of IL-4 while neutralizing endogenously produced IL-4 abolished IL-4 production similarly in atopic and healthy T cells. A subset of effector T cells acquired the expression of the cutaneous lymphocyte antigen (CLA). The frequency of CLA+ T cells was not different between atopic and healthy donors. CLA+ T cells, differentiated from naïve atopic, but not healthy T cells, showed a preferential Th2 cytokine profile as assessed by intracellular cytokine staining. Also effector T cells derived from atopic patients without dermatitis tended to show this imbalance, although it was not significantly different to healthy controls. This Th2 cytokine profile did not develop when naïve T cells were cultured in the presence of IL-12. In conclusion, high IL-4 production in developing T cells from AD patients was associated with CLA expression, the net IL-4 production of all effector CD4+ T cells, however, was similar to IL-4 production by T cells from healthy donors.

Optimisation of the CT h4S bioassay for detection of human interleukin-4 secreted by mononuclear cells stimulated by phytohaemaglutinin or by human leukocyte antigen mismatched mixed lymphocyte culture

Limiting dilution analysis has been used in the context of allogeneic bone marrow transplantation to determine anti-recipient interleukin-2 (IL-2) producing helper T lymphocyte precursor (HTLp) frequencies, which in several studies have been predictive of graft-versus-host disease (GVHD). Recently high anti-recipient IL-4 producing HTLp frequencies have been reported and associated with a decreased risk of GVHD. The aim of the present study was to define the optimal conditions for combined determination of IL-2 and IL-4 producing anti-recipient HTLp frequencies. We have optimised the CT.h4S bioassay with regards to specificity, sensitivity, detection limit, and reproducibility. We have found the optimal assay conditions to be 1 x 10 (4) CT.h4S cells/well deprived of IL-4 for 24 h and preincubated for 7 h followed by 18 h of incubation with tritiated methyl-thymidine. In this setting the CT.h4S bioassay detects 5 pg/ml of human recombinant IL-4 with no detection of IL-2 in concentrations below 500 pg/ml. We have found 72 h of culture optimal for detection of IL-2 and IL-4 produced by human mononuclear cells (MNC) in response to stimulation with phytohaemaglutinin and for detection of IL-2 in human leukocyte antigen (HLA)-mismatched mixed leukocyte culture (MLC). An interindividual variation in cytokine accumulation was demonstrated for IL-4 but not for IL-2. With the use of 5x10(4) responder cells/well no IL-4 could be detected in HLA-mismatched MLC between days 1 and 16. The lack of IL-4 detection was not due to high amounts of soluble IL-4 receptor. With the use of 1x10(6) responder cells/well in HLA-mismatched MLC, we found limited IL-4 accumulation still increasing at day 12. We conclude that the CT.h4S bioassay is a reliable and specific method for quantification of IL-4 accumulation in cultures of human MNC. The difference in optimal timing for IL-2 (day 3) and IL-4 (>/=day 12) detection and evidence of very low IL-4 producing HTLp frequencies makes the relevance of a combined IL-2/IL-4 HTLp assay questionable.

Interleukin-4 and breast cancer

IL-4 is a pleiotropic cytokine produced by T lymphocytes which acts on various cells of such as T and B lymphocytes, monocytes, fibroblast, endothelial cells, macrophages and some others. IL-4 was originally described as a B cell growth factor, and now known to provide potent anti-tumor activity against various tumors, including breast cancer. IL-4 can induce apoptosis in cultured breast cancer cells. In addition, it has been clarified that IL-4 plays an important role in the regulation of estrogen synthesis enzymes including 17beta-HSD and 3beta-HSD. These findings imply that IL-4 is a key enzyme not only for Th2 type immune reactions but also for tumor cell growth itself in human breast cancer.

An enzyme immunoassay for detection of Japanese encephalitis virus-induced chemotactic cytokine

Japanese encephalitis virus (JEV) induces human peripheral blood monocytes to secrete a chemotactic cytokine [human macrophage-derived factor (hMDF)] which causes chemotaxis of neutrophils. The only known assay for hMDF cannot quantify its level in samples, so an enzyme immunoassay has been standardized for detection of hMDF and hMDF-specific antibodies in test samples. The reported enzyme linked immunosorbent assay (ELISA) was found to be sensitive (89%), specific (91%), accurate (92 2%) and reproducible and was able to detect a minimum concentration of 23 ng hMDF/ml in test samples. The chemotactic factor could be detected in JEV inoculated mouse sera and JEV infected culture fluids. Significant finding of the test was the detection of hMDF in sera of human cases of JE.

Enhancement of human IL-4 activity by soluble IL-4 receptors in vitro

The recombinant form of the extracellular domain of the IL-4 receptor (sIL-4R) is a potential candidate to neutralize IL-4; however, murine sIL-4R displayed both antagonistic and agonistic activity in vivo. Here we show that human recombinant sIL-4R induced the formation of complexed IL-4 in supernatants of activated T cells in a dose-dependent manner as measured by newly developed enzyme-linked immunosorbent assays. These IL-4/sIL-4R complexes liberated free IL-4 even after prolonged culturing. In contrast, in the absence of exogenously added sIL-4R, free IL-4 was rapidly consumed or proteolytically degraded in cultures of activated T cells. Thus, no IL-4 bioactivity could be determined in supernatants of T cells activated in the presence of IL-4 for 6 days. In contrast, the same cultures carried out in the presence of sIL-4R showed marked IL-4 bioactivity. While low concentrations of sIL-4R enhanced IL-4-driven inhibiton of IFN-gamma production by activated T cells, higher concentrations neutralized IL-4. Together, human sIL-4R, besides its activity as an antagonist to IL-4, also possesses protective and agonistic functions for IL-4, which may be relevant for clinical studies aiming to neutralize IL-4 in vivo.