The phosphodiesterase inhibitors pentoxifylline and rolipram prevent diabetes in NOD mice

Interleukin (IL)-12, interferon (IFN)-gamma, and other inflammatory cytokines play an important role in the pathogenesis of autoimmune insulitis and diabetes in NOD mice, and inhibition of these cytokines is likely to be beneficial. In this study, we found that Pentoxifylline (PTX) and Rolipram (phosphodiesterase [PDE] inhibitors that induce increased intracellular cAMP) can block inflammatory cytokine production. Inhibition of IL-12 and IFN-gamma secretion was demonstrated in macrophages activated with lipopolysaccharide or T-cells stimulated through the CD3/T-cell receptor complex, respectively. Moreover, strong inhibition of IL-12 was demonstrated in vivo in superantigen-immunized mice. Rolipram was inhibitory at concentrations as low as 10(-8) to 10(-7) mol/l, and on a molar basis, it was 100-fold more effective than PTX. Tumor necrosis factor-alpha was also inhibited, but IL-4 was less sensitive to suppression. In NOD mice, both PTX and Rolipram reduced the severity of insulitis and prevented diabetes, with or without cyclophosphamide administration (which precipitates onset of disease). This protection of NOD mice was still apparent over 10 weeks after withdrawal of the drug treatment. It appears that blocking the activity of type IV PDE is sufficient to mediate the effects reported in this study, since Rolipram inhibits only this isoform, unlike PTX (a general inhibitor). PTX and Rolipram may be effective in the treatment of autoimmune diabetes or other conditions characterized by excessive production of inflammatory cytokines.

Expression of the costimulatory receptor CD30 is regulated by both CD28 and cytokines

Costimulation was originally defined and characterized during primary T cell activation. The signaling events that regulate subsequent antigen encounters by T cells are less well defined. In this study we examined the role of CD30 in T cell activation and defined factors that regulate expression of CD30 on T cells. We demonstrate that CD30 expression is restricted to activated T cells and regulated by CD28 signal transduction. In contrast to CD28-expressing TCR Tg cells, CD28-deficient TCR Tg cells did not express CD30 when cultured with peptide and APCs. However, rIL-4 reconstituted CD30 expression on CD28-deficient TCR Tg cells. Blockade of CD28 interactions or depletion of IL-4 inhibited the induction of CD30, suggesting that both CD28 and IL-4 play important roles in the induction of CD30 expression on wild-type cells. However, CD28 signaling did not up-regulate CD30 expression solely through its ability to augment IL-4 production because IL-4-deficient T cells stimulated with anti-CD3 and anti-CD28 expressed CD30. Induction of CD30 in the absence of IL-4 was not due to the IL-4-related cytokine IL-13. CD30, when expressed on an activated T cell, can act as a signal transducing receptor that enhances the proliferation of T cells responding to CD3 crosslinking. Collectively, the data suggest that T cell expression of CD30 is dependent on the presence of CD28 costimulatory signals or exogenous IL-4 during primary T cell activation. Once expressed on the cell surface, CD30 can serve as a positive regulator of mature T cell function.

Corticosteroids enhance the capacity of macrophages to induce Th2 cytokine synthesis in CD4+ lymphocytes by inhibiting IL-12 production

We investigated the effects of corticosteroids on IL-12 production by mouse splenic adherent cells and the subsequent capacity of these cells to induce cytokine production by CD4+ T cells. To distinguish the effects of corticosteroids on APCs from those on T cells, only the APCs and not the T cells were exposed to corticosteroids. Treatment of splenic adherent cells with dexamethasone greatly inhibited production of IL-12, a cytokine known to enhance IFN-gamma synthesis and decrease IL-4 synthesis by CD4+ T cells. The reduction in IL-12 production by corticosteroid-treated macrophages decreased their ability to induce IFN-gamma and increased their ability to induce IL-4 synthesis in Ag-primed CD4+ T cells. Splenic adherent cells from mice treated in vivo with dexamethasone also displayed a reduced capacity to produce IL-12. These results help to resolve previous conflicting observations regarding the effects of corticosteroids on cytokine production by T cells, and indicate that while corticosteroids may directly inhibit Th1 and Th2 cytokine production in T cells, corticosteroids, by reducing IL-12 production in APCs, have the potential to indirectly enhance Th2 cytokine synthesis. Therefore, treatment of diseases such as allergy with chronic corticosteroids may indirectly exacerbate the course of the disease, which is caused primarily by the overproduction of Th2 cytokines in allergen-specific CD4+ T cells.

Strength of TCR signal determines the costimulatory requirements for Th1 and Th2 CD4+ T cell differentiation

Differentiation of naive CD4 T cells into cytokine-secreting effector Th1 and Th2 cells is influenced by several factors. We have previously reported that the affinity of antigen for TCR and antigen dose can influence the differentiation of Th1 and Th2 cells. Several in vitro and in vivo models have demonstrated a role for the costimulatory molecules, B7-1 (CD80) and B7-2 (CD86), in the generation of distinct effector T cell responses. To determine whether the strength of TCR signaling controls the involvement of CD28 costimulation in selective CD4 T cell differentiation, naive CD4 T cells bearing a transgenic TCR are primed by a weak or strong TCR signal (signal 1) in the presence or absence of B7 costimulatory molecules (signal 2). In this system, IL-4-producing Th2 cells are generated by priming with a weak but not a strong TCR signal. Th2 cell differentiation is dependent on CD28/B7 interactions in that disruption of CD28/B7 interactions inhibits the priming of Th2 cells and cross-linking CD28 with anti-CD28 antibody augments the priming of Th2 cells. In contrast, however, IL-4-producing Th2 cells cannot be generated by priming with a strong TCR signal even in the presence of strong costimulation or high doses of IL-2. Thus, our results suggest that naive CD4 T cells are receptive to CD28-dependent IL-4 production only if they receive a weak TCR signal.

Interleukin 4 responses in acute leukaemia patients with severe chemotherapy-induced leucopenia

T lymphocyte functions in acute leukaemia patients with severe chemotherapy-induced leucopenia were investigated using 3 different approaches: (i) analysis of serum concentrations of the T cell cytokine interleukin 4 (IL4) demonstrated that serum IL4 levels increased during complicating bacterial infections. However, this response was modulated by a concomitant increase in serum levels of the potential IL4 antagonist soluble IL4 receptor alpha chain (sIL4R alpha). (ii) Even during leucopenia a subset of T lymphocytes derived from leucopenic patients expressed the activation markers CD25 (IL2 receptor), CD71 (transferrin receptor) and HLA-DR. (iii) Subsets of circulating CD4+ and CD8+ T lymphocytes could undergo clonogenic proliferation in vitro, and a majority of these clones secreted IL4. CD4+ clones showed higher IL4 levels than CD8+ clones. Our results indicate that T lymphocytes can be activated and contribute to cytokine responses in acute leukaemia patients with severe chemotherapy-induced cytopenia.

CTL generation in the presence of IL-4 is inhibited by free p40: evidence for early and late IL-12 function

The cytokine requirements for the generation of a CTL response were examined using thymocyte responders stimulated with Con A. In agreement with previous reports, IL-4 alone can generate a strong CTL response. To determine whether IL-12 was required for this response, we added either a neutralizing Ab against IL-12 or an antagonist of IL-12 function, p40. Both anti-IL-12 and p40 were found to inhibit the generation of CTL in the presence of IL-4. Consistent with these data, exogenous IL-12 was found to synergize with IL-4, particularly, when IL-4 was added at levels unable to generate a CTL response alone. This synergistic response was observed whether IL-12 was added at the beginning of culture along with IL-4 or after the first day to cultures initiated with IL-4. Likewise, the combination of IL-2 plus IL-12 evoked a strong synergistic response when cultures were initiated with IL-2 and IL-12 was added initially or after the first day of culture. Addition of either IL-2 or IL-12 alone did not generate a response. In contrast to these data showing that IL-12 was able to signal late in culture, p40 inhibited CTL generation in response to IL-4 only when added at the beginning of culture. These results imply that CTL induction involves a crucial early IL-12 signal, which once delivered permits cells to respond to a later IL-12 signal. These data are consistent with the idea that free circulating p40 could inhibit the generation of CTL by antagonizing the early IL-12 "differentiation" signal.

Protection from autoimmune diabetes by adjuvant therapy in the non-obese diabetic mouse: the role of interleukin-4 and interleukin-10

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease that is characterized by the destruction of insulin-producing beta-cells in the pancreatic islets. A single administration of CFA prevents clinical hyperglycaemia in non-obese diabetic (NOD) mice. We have previously shown that CFA administration does not eliminate insulitis in the pancreas of the treated animals, but diverts the disease process from a destructive to a non-destructive pathway. We provide evidence that this phenomenon may be under cytokine control. Neutralizing monoclonal antibodies against IL-4 and IL-10 were injected, singularly or in combination, into CFA-treated NOD mice. Antibody treatment did not lead to the development of overt diabetes; however, a marked impairment of glucose tolerance was shown in about one half of the mice treated with a combination of the two antibodies at the end of the study. This functional abnormality correlated with the histological loss of pancreatic islet tissue. These studies suggest a role for IL-4 and IL-10 in CFA-induced protection from diabetes in the NOD mouse. They also suggest that, in this animal model, the nature of the autoimmune response to islet tissue (either destructive or non-destructive) may reflect the relative proportion of Th1- and Th2-type cytokines produced in the lesions.

An interleukin (IL)-13 receptor lacking the cytoplasmic domain fails to transduce IL-13-induced signals and inhibits responses to IL-4

Interleukin (IL)-13 is a pleiotropic immunoregulatory cytokine that shares many, although not all, of the biological activities of IL-4. The overlapping biological properties of IL-4 and IL-13 appear to be due to the existence of shared components of the receptors, and we and others showed that the IL-4 receptor-alpha is involved in signal transduction paths activated by both. We show here that expression of the IL-13 receptor-alpha in two factor-dependent cell lines, the premyeloid FD5 and the T lymphoid CT4.S, conferred the ability to grow continuously in response to IL-13; to respond to IL-13 with tyrosine phosphorylation of JAK1, Tyk2, IL-4Ralpha, IRS-2, and STAT6; and to respond to IL-4 with tyrosine phosphorylation of Tyk2 in addition to those induced in parental cell lines. Expression of a truncated IL-13 receptor-alpha that lacked the cytoplasmic domain demonstrated that this domain was essential for IL-13-dependent growth and phosphorylation of the above substrates. Expression of this truncated IL-13 receptor also resulted in an inhibition of biochemical and biological responses to IL-4 that was exacerbated by the presence of IL-13. These dominant inhibitory effects indicate that the extracellular domain of the truncated IL-13 receptor competes with gammac for complexes of IL-4 and the IL-4 receptor-alpha, or, when itself bound to IL-13, competes with IL-4 for the IL-4 receptor-alpha.

Aqueous humor induces transforming growth factor-beta (TGF-beta)-producing regulatory T-cells

PURPOSE

The intraocular microenvironment is an immune-privileged site where immunogenic inflammation is suppressed. Suppression of immunogenic inflammation has been associated with immunosuppressive factors found in aqueous humor produced by ocular tissues. To further understand the mechanisms suppressing immunogenic inflammation in the eye, we have examined the production of lymphokines by primed T-cells activated in the presence of aqueous humor.

METHODS

Enriched in vivo primed T-cells were T-cell receptor-stimulated in the presence of fresh aqueous humor. The culture supernatant was assayed for IFN-gamma and IL-4 by sandwich ELISA. TGF-beta production by T-cells stimulated in the presence of aqueous humor was assayed by a TGF-beta bioassay of the culture supernatant and by quantitative RT-PCR for TGF-beta 1 mRNA expression. Aqueous humor-treated T-cells were assayed for their capacity to suppress IFN-gamma production by stimulated, primed T-cells.

RESULTS

Aqueous humor-enhanced proliferation but irreversibly suppressed production of both IFN-gamma and IL-4 by in vitro-activated, in vivo-primed T-cells. Aqueous humor induced in vivo primed T-cells to produce TGF-beta in vitro, and these TGF-beta-producing T-cells suppressed IFN-gamma production by other T-cells activated in co-cultures.

CONCLUSIONS

Aqueous humor alters the functional program of TCR-ligand-activated, primed T-cells, converting the cells to TGF-beta-producing regulatory cells.

In vivo IL-12 administration induces profound but transient commitment to T helper cell type 1-associated patterns of cytokine and antibody production

There is much interest in the utility of exogenous IL-12 as a biologic adjuvant in immediate hypersensitivity and infectious or parasitic diseases where the induction of Th1 responses is strongly associated with protective immunity. Using an immediate hypersensitivity model in which C57Bl/6 mice immunized with OVA (alum) normally generate Th2-dominated responses, we examined the ability of rIL-12 to direct and maintain OVA-specific cytokine and Ab responses in a Th1 direction. Exogenous IL-12 administered coincident with OVA immunization stimulated elevated serum IFN-gamma levels, enhanced IFN-gamma synthesis, and inhibited IL-4 synthesis in bulk culture; 80 to 99% inhibited primary Ag-specific serum IgE and IgG1 responses; and 15- to 20-fold enhanced IgG2a synthesis. However, each of these effects was highly transient, as exogenous IL-12, given at levels up to those associated with serious toxicity, failed to have a lasting impact on the OVA-specific T or B cell response. This transience was evident in primary bulk culture cytokine synthesis; in limiting dilution analysis of the frequency of OVA-specific IFN-gamma-, IL-4-, or IL-10-producing CD4 T cells; and, most importantly, in vivo effector responses such as IgE production to secondary and tertiary OVA immunization. The finding that the intense Th1-like phenomena seen following in vivo administration of rIL-12 with this exogenous Ag are highly transient and are not associated with alterations in the allergen-specific CD4 T cell repertoire to Th1-like patterns suggests a need for caution in the enthusiasm for the use of this cytokine as a biologic adjuvant.

Induction of protective Th1 responses to Candida albicans by antifungal therapy alone or in combination with an interleukin-4 antagonist

Resistance or susceptibility to disseminated and mucosal Candida albicans infections in mice correlates with the development of protective or nonprotective T helper (Th) cell responses. To determine whether immunomodulatory activity on Th cell functions is an effect beyond that provided by antifungal therapy, mice with disseminated or gastrointestinal infection were treated with amphotericin B or fluconazole and assessed for mortality, fungus burden in the organs, and parameters of Th cell-dependent immunity. Both antimycotics produced protective CD4+ Th1 cell responses, as revealed by increased production of interleukin (IL)-12 and interferon-y, decreased production of IL-4, delayed-type hypersensitivity to fungal antigen, and the disappearance of antigen-specific IgE. Concomitant neutralization of endogenous IL-4 greatly increased the antifungal efficacy and the Th1-promoting activity of both agents. These results indicate that successful antifungal therapy alone or in combination with cytokine antagonists may rely on the induction of an appropriate Th antifungal cell response.

Mouse macrophage development in the absence of the common gamma chain: defining receptor complexes responsible for IL-4 and IL-13 signaling

The common gamma chain (gamma c) forms a critical component of the receptors for interleukins (IL)-2, IL-4, IL-7, IL-9, and IL-15. We analyzed gamma c-deficient mice to define a role for gamma c signaling in the development and function of the macrophage lineage. No major differences in absolute cell numbers, cell surface phenotype, or in vitro function of gamma c- compared to gamma c+ macrophages were observed. We therefore conclude that signaling through the gamma c chain is not essential for the differentiation of mouse macrophages. Although B and T cells require gamma c for IL-4 responses, IL-4 up-regulated major histocompatibility class II molecules and inhibited nitric oxide production from gamma c- macrophages following stimulation with lipopolysaccharide and interferon-gamma. gamma c- macrophages could also respond to IL-13, consistent with the model of a type II IL-4 receptor alpha/IL-13R which can function in the absence of gamma c. Both IL-4 and IL-13 responses could be completely inhibited with the mouse IL-4 antagonist OY, suggesting that all of the observed IL-13 responses pass through the type II receptor, making it the primary signaling receptor complex for IL-13 in mouse macrophages.

Interleukin-5 and eosinophils induce airway damage and bronchial hyperreactivity during allergic airway inflammation in BALB/c mice

The cytokines IL-4 and IL-5 secreted from antigen-activated CD4+ T cells are thought to play central roles in the clinical expression and pathogenesis of asthma. However, there is conflicting evidence in animal models of allergic airway inflammation as to the relative importance of IL-5 and eosinophils to the mechanisms underlying the induction of bronchial hyperreactivity and morphological changes to the airways in response to aeroallergen. In a recent investigation, the development of aeroallergen-induced bronchial hyperreactivity in BALB/c mice was thought to be exclusively regulated by IL-4, with no role for IL-5 or eosinophils being demonstrated. In contrast, allergic airway disease could not be induced in IL-5-deficient mice of the C57BL/6 strain. A model of allergic airway inflammation, which displays certain phenotypic characteristics of late-phase asthmatic responses, was used in the present investigation to establish a role for IL-5 and eosinophils in the initiation of bronchial hyperreactivity and in the pathogenesis of allergic airway disease in BALB/c mice. Sensitization and repetitive aerosolization of mice with ovalbumin resulted in a severe airway inflammatory response which directly correlated with the induction of extensive airway damage and bronchial hyperreactivity to beta-methacholine. Treatment of mice with anti-IL-5 mAb before aeroallergen challenge, abolished blood and airway eosinophilia, lung damage and significantly reduced bronchial hyperreactivity. These results show that IL-5 and eosinophilic inflammation play a substantial role in the pathophysiology of allergic airway disease and, moreover, that aeroallergen-induced bronchial hyperreactivity is not exclusively regulated by IL-4. These results also suggest that eosinophils are predominantly responsible for regulating aeroallergen-induced structural changes to the airways which contribute, in part, to the mechanism underlying the induction of bronchial hyperreactivity. Thus, there are at least two distinct pathophysiological mechanisms for the induction of aeroallergen-induced airway occlusion.

IL-4 receptor complexes containing or lacking the gamma C chain are inhibited by an overlapping set of antagonistic IL-4 mutant proteins

IL-4 signals on lymphocytes and other cells through a heterodimeric complex of two cytokine receptor proteins, IL-4R alpha and gamma C. IL-4 variants with mutations in the positions Tyr124, and (less efficiently) Arg121 and Ser125 are deficient in interaction with gamma zero and can be applied as IL-4 antagonists. Some cells respond to IL-4 without using gamma zero presumably by recruiting an alternative subunit into the receptor complex. We have investigated the effects of IL-4 mutant proteins on cells bearing this second type of IL-4 receptor complex. Mutations in the amino acid residues Arg 121 and Tyr124, but not Ser125, completely prevented cellular responses mediated by type 2 IL-4 receptors. Both receptor types are therefore affected by mutations in an overlapping but not identical site of the IL-4 molecule.

Requirement of CD28-CD86 co-stimulation in the interaction between antigen-primed T helper type 2 and B cells

The interaction between CD28 and its ligands, CD80 and CD86, is crucial for an optimal activation of antigen-specific T cells. However, the requirement of CD80 or CD86 co-stimulation in Th2 cell differentiation and activation is controversial. Freshly isolated murine CD4+ and CD8+ T cells were incubated with P815 transfectants expressing a similar level of either CD80 or CD86 in the presence of anti-CD3 mAb. Both CD80 and CD86 co-stimulated the proliferation of CD4+ and CD8+ T cells at comparable time-kinetics and magnitude, but CD86 alone was able to co-stimulate IL-4 and especially IL-10 production in CD4+ T cells. In typical Th2-dependent immune responses elicited by Nippostrongylus brasillensis infection, the anti-CD86 mAb treatment but not the anti-CD80 mAb treatment efficiently inhibited antigen-specific IgE and IgG1 production, which was accompanied with the reduced IL-4 production. Our results suggest that CD86 co-stimulation plays a dominant role not only in the primary activation of Th2 cells but also in the secondary interaction between antigen-primed Th2 cells and B cells.

Th1 CD4+ cells adoptively transfer experimental hypersensitivity pneumonitis

Cultured cells from Micropolyspora faeni-sensitized donors can adoptively transfer murine experimental hypersensitivity pneumonitis (EHP). To determine whether the CD4+ cells responsible for transfer have characteristics of Th1 or Th2 cells, we established cell lines from lung-associated lymph nodes of M. faeni-sensitized C3H/HeJ mice by culturing with antigen and either IFN-gamma, IL2, and anti-IL4, or IL4. Cell lines were stimulated regularly with antigen, fresh antigen-presenting cells, and the cytokine/anti-cytokine antibody cocktail. At various times after initiation of culture, cells were injected intravenously into recipients, which were then challenged intratracheally with M. faeni and sacrificed and the extent of pulmonary inflammatory response was determined. IFN-gamma, IL4, and IL10 levels were determined in supernatants of cell cultures stimulated with M. faeni to characterize the cell lines as Th1 (IFN-gamma, but low IL4 and IL10 secretion) or Th2 (IL4 and IL10, but low IFN-gamma secretion). Cell lines were differentiated into either Th1 (IFN-gamma = 310 +/- 45 U/ml, IL4 = 0.10 +/- 0.1 U/ml, IL10 = 1750 +/- 75 pg/ ml, >99% CD4+) cell lines by Day 16 of culture or Th2 cell lines (IFN-gamma = 1.8 +/- 1.0 U/ml, IL4 = 830 +/- 388 U/ml, IL10 = 51,700 +/- 10,900 pg/ml, >96% CD4+) by Day 30. Th1 cell lines were able to adoptively transfer EHP whereas Th2 cell lines were unable to adoptively transfer EHP. The ability to transfer EHP was directly related to the amount of IFN-gamma and inversely to the amount of IL4 secreted by antigen-stimulated cells. We conclude that it is possible to produce CD4+ cell lines with either Th1 or Th2 characteristics from lung-associated lymph nodes of mice exposed to M. faeni and that only Th1 CD4+ cell lines can adoptively transfer EHP.

Role of costimulators in T cell differentiation: studies using antigen-presenting cells lacking expression of CD80 or CD86

For T cells to be optimally activated, recognition of Ag/MHC complexes by the TCR must be accompanied by a second, costimulatory signal that can be provided efficiently by the related costimulatory molecules CD80 (B7-1) and CD86 (B7-2). Recently, CD80 and CD86 have been implicated as differential determinants of Th1- vs Th2-type cytokine profiles. However, this remains a controversial issue since conflicting results have been obtained in different experimental models both in vivo and in vitro. To investigate the role of CD80 and CD86 in Th subset differentiation, we have examined the cytokine profiles induced in TCR transgenic T cells stimulated by peptide in association with splenic APCs obtained from knockout mice that selectively lack expression of either the CD80 or the CD86 molecule. Our data suggest that CD86, and to a lesser extent CD80, can make significant contributions to the production of both IL-4 and IFN-gamma. However, neither molecule plays an obligatory role in priming for the production of either effector cytokine. Furthermore, CD80 and CD86 contribute to the magnitude of T cell activation, but do not appear to selectively regulate Th1 vs Th2 differentiation.

Roles of IL-4 and IFN-gamma in stabilizing the T helper cell type 1 and 2 phenotype

It has previously been reported that Th1 CD4 T cell populations can be converted to IL-4 producers, whereas Th2 populations are refractory to IL-12-mediated IFN-gamma production. We have recently shown that CD30 is a marker for the IL-4 response and have therefore used CD30 here to study Th1 and Th2 commitment. We show that Th2 cell populations normally show a stable phenotype and fail to respond to IL-12 because of endogenous IL-4 production. IFN-gamma abrogates this antagonistic effect of IL-4 and permits the conversion of Th2 populations to IFN-gamma producers by IL-12. In the complete absence of IL-4, however, IFN-gamma is not required for this transformation, and Th1 cells generated by IL-12 become committed to the Th1 pathway and lose the ability to respond to IL-4. Thus, the balance between local IL-4 and IFN-gamma in an immune response is a key factor in determining the outcome of the CD4 effector T cell response.

A murine interleukin-4 antagonistic mutant protein completely inhibits interleukin-4-induced cell proliferation, differentiation, and signal transduction

We characterize here a highly efficient antagonist for interleukin-4 (IL-4) in the mouse system. In this double mutant of the murine IL-4 protein, both glutamine 116 and tyrosine 119 were substituted by aspartic acid residues. This variant (QY) bound with similar affinity to the IL-4 receptor alpha subunit as wild type IL-4 without inducing cellular responses. In contrast, QY completely inhibited in a dose-dependent manner the IL-4-induced proliferation of lipopolysaccharide-stimulated murine splenic B-cells, of the murine T cell line CTLL-2, and of the murine pre-B-cell line BA/F3. QY also inhibited the IL-4-stimulated up-regulation of CD23 expression by lipopolysaccharide-stimulated murine splenic B-cells and abolished tyrosine phosphorylation of the transcription factor Stat6 and the tyrosine kinase Jak3 in IL-4-stimulated BA/F3 cells. Selective inhibition of IL-4 may be beneficial in T-helper cell type 2-dominated diseases, like type I hypersensitivity reactions or helminthic infections. The QY mutant could be an attractive tool to study in vivo the therapeutic potential of IL-4 antagonists in mouse systems.

Evidence for the participation of interleukin-2 (IL-2) and IL-4 in the regulation of autonomous growth and tumorigenesis of transformed cells of lymphoid origin

In the current study, we investigated the role of interleukin-2 (IL-2) and IL-4 as autocrine growth factors responsible for autonomous growth of four murine tumor cell lines: LSA, a radiation leukemia virus-induced T-cell lymphoma; EL-4, a chemically triggered T-cell lymphoma; PE-3T, a T-cell line that underwent spontaneous transformation ex vivo; and P815, a mastocytoma. All tumor cell lines screened constitutively expressed IL-2 receptor (IL-2R) and IL-4R genes. However, only LSA and PE-3T cells expressed IL-2 and IL-4 genes constitutively, whereas EL-4 and P815 tumor cells expressed only IL-4 but not IL-2. Monoclonal antibodies (MoAbs) against IL-2, IL-4, or a combination of these, as well as MoAbs against IL-2R significantly inhibited the proliferation of LSA but not that of other tumor cell lines ex vivo. To exclude the possibility that, in other tumor cell lines, the autocrine growth factor may interact with its receptor within the cell, the ability of antisense phosphorothioate oligonucleotides to inhibit the growth of the tumor cells was tested. The antisense phosphorothioate oligonucleotides specific for IL-2, IL-4, IL-2R beta, or IL-2R gamma chains, added in culture, could markedly inhibit the growth of LSA but not that of the other tumor cell lines screened. Inasmuch as IL-2R beta and IL-2R gamma subunits also serve as a component of the receptors for IL-4, IL-7, IL-9, and IL-15, the above data suggested that such cytokine redundancy was not responsible for autonomous growth of the other tumor cell lines. Addition of exogenous IL-2 or IL-4 to the tumor cell cultures caused significant enhancement in the proliferation of PE-3T cells, whereas other cell lines were either not significantly affected or slightly inhibited from growing. Interestingly, the LSA tumor growth in nude mice was significantly inhibited after treatment of these mice with a combination of MoAbs against IL-2 and IL-4. Together, our studies show for the first time that IL-2 and IL-4 may serve as autocrine growth factors in the autonomous proliferation of tumor cells, particularly those that are retrovirally induced. Second, some tumor cell lines, despite expressing certain cytokines and their receptors constitutively, may not depend exclusively on such factors for autocrine growth.

Analysis of thymic stromal cell subpopulations grown in vitro on extracellular matrix in defined medium--V. Proliferation regulating activities in supernatants of human thymic epithelial cell cultures

In previous reports in this series, we described the growth conditions, morphology and supernatant activities of human thymic epithelial cell cultures. The human thymic epithelial cell supernatant (HTES) contained IL-6, G-CSF activities and exhibited a strong enhancing effect on thymocyte proliferative response to mitogens, which was identified as IL-6 related. The responding thymocyte population was apparently identified as PNA, mature T cells. In order to simplify further analysis of HTES activities, we selected to use a well-defined mature murine T cell clone which has a Th2 phenotype (8-5 clone). HTES induced 8-5 cell proliferation without the presence of antigen, antigen presenting cells (APC) or mitogens. This enhancing effect of HTES was completely blocked with anti hIL-6 antibody but could not be reproduced by rhIL-6 alone. Hence, IL-6 is a necessary but insufficient factor in mediating this effect. HTES induced proliferation was accompanied by endogenous IL-4 secretion from 8-5 cells. Furthermore, the proliferation was blocked by anti mIL-4 antibody, implicating IL-4 as an autocrine growth factor in this system. HTES increased also the expression of IL-2 receptor. In addition, rhIL-2 and rmIL-4 each has a synergistic effect on the proliferative response of 8-5 cells to HTES. A similar synergistic activity was demonstrated when rhIL-6 was used instead of HTES, suggesting that IL-6 regulates some HTES activities. Our findings indicate that HTES activities, of which IL-6 is only part, are mediated via the induction of autocrine growth factors and by the regulation of T cell growth factor receptor expression.

Effect of CD80 and CD86 blockade and anti-interleukin-12 treatment on mouse acute graft-versus-host disease

We investigated the efficacy of a combination of anti-CD80 and CD86 (CD80 + 86) monoclonal antibodies (mAb), anti-interleukin (IL)-12 mAb, or both, for prophylaxis in a mouse acute graft-versus-host-disease (GVHD) model. The treatment with a combination of anti-CD80 + 86 mAb efficiently reduced the lethality of GVHD, whereas mAb against either CD80 or CD86 alone had an effect. A delay in lymphocyte reconstitution and GVHD-associated histological changes in organs was observed at 30 days post-bone marrow transplantation (BMT) even in the anti-CD80 + 86 mAb-treated mice, although these manifestations were resolved by 100 days. In vitro, host alloantigen-specific T cell proliferative responses and generation of CTL were significantly reduced by anti-CD80 + 86 treatment. Furthermore, anti-CD80 + 86 mAb preferentially inhibited the production of interferon (IFN)-gamma, but not IL-4 and IL-10, when cultures were assayed at 21 days. Although the anti-IL-12 mAb treatment alone inhibited the generation of cytotoxic T lymphocytes and IFN-gamma production in vitro, administration of anti-IL-12 mAb in vivo reversed the beneficial effects of anti-CD80 + 86 treatment on host survival post-BMT. The adverse effect of anti-IL-12 treatment seems to result from impairment of natural immunity and hematopoiesis, rather than as a consequence of an incomplete blockade of T helper (Th)1 responses. Our results suggest that the prevention of GVHD-induced death results from the efficient blockade of Th1 cell activation by the anti-CD80 + 86 treatment. However, further treatment is required for a complete prevention of GVHD, which seems to be partly mediated by Th2 cells.