Identification of a novel thymocyte growth-promoting factor derived from B cell lymphomas

Immunosuppressive Mechanisms of Malignant Gliomas: Parallels at Non-CNS Sites

The central nervous system (CNS) possesses powerful local and global immunosuppressive capabilities that modulate unwanted inflammatory reactions in nervous tissue. These same immune-modulatory mechanisms are also co-opted by malignant brain tumors and pose a formidable challenge to brain tumor immunotherapy. Routes by which malignant gliomas coordinate immunosuppression include the mechanical and functional barriers of the CNS; immunosuppressive cytokines and catabolites; immune checkpoint molecules; tumor-infiltrating immune cells; and suppressor immune cells. The challenges to overcoming tumor-induced immunosuppression, however, are not unique to the brain, and several analogous immunosuppressive mechanisms also exist for primary tumors outside of the CNS. Ultimately, the immune responses in the CNS are linked and complementary to immune processes in the periphery, and advances in tumor immunotherapy in peripheral sites may therefore illuminate novel approaches to brain tumor immunotherapy, and vice versa.

B cells responses and cytokine production are regulated by their immune microenvironment

The adaptive immune system consists of two types of lymphocytes: T and B cells. These two lymphocytes originate from a common precursor, yet are fundamentally different with B cells mediating humoral immunity while T cells mediate cell mediated immunity. In cytokine production, naïve T cells produce multiple cytokines upon activation while naïve activated B cells do not. B cells are capable of producing cytokines, but their cytokine production depends on their differentiation state and activation conditions. Hence, unlike T cells that can produce a large amount of cytokines upon activation, B cells require specific differentiation and activation conditions to produce cytokines. Many cytokines act on B cells as well. Here, we discuss several cytokines and their effects on B cells including: Interleukins, IL-7, IL-4, IL-6, IL-10, and Interferons, IFN-α, IFN-β, IFN-γ. These cytokines play important roles in the development, survival, differentiation and/or proliferation of B cells. Certain chemokines also play important roles in B cell function, namely antibody production. As an example, we discuss CCL28, a chemokine that directs the migration of plasma cells to mucosal sites. We conclude with a brief overview of B cells as cytokine producers and their likely functional consequences on the immune response.

TSPAN33 is a novel marker of activated and malignant B cells

We have identified Tspan33 as a gene encoding a transmembrane protein exhibiting a restricted expression pattern including expression in activated B cells. TSPAN33 is a member of the tetraspanin family. TSPAN33 is not expressed in resting B cells, but is strongly induced in primary human B cells following activation. Human 2E2 cells, a Burkitt's lymphoma-derived B cell model of activation and differentiation, also upregulate TSPAN33 upon activation. TSPAN33 is expressed in several lymphomas including Hodgkin's and Diffuse large B cell lymphoma. TSPAN33 is also expressed in some autoimmune diseases where B cells participate in the pathology, including rheumatoid arthritis patients, systemic lupus erythematosus (SLE), and in spleen B cells from MRL/Fas(lpr/lpr) mice (a mouse model of SLE). We conclude that TSPAN33 may be used as a diagnostic biomarker or as a target for therapeutic antibodies for treatment of certain B cell lymphomas or autoimmune diseases.

[Alopecia areata in animal models--new insights into pathogenesis and treatment of a T cell-mediated autoimmune disorder]

Alopecia areata is a common disease, but for ethical reasons it seems difficult to perform large-scale studies to elucidate the pathogenesis and to develop new therapeutic approaches in man. It is therefore helpful to develop appropriate animal models. The Dundee experimental bald rat (DEBR) and the C3H/HeJ mouse are well-established animal models for alopecia areata and can be used for the study of genetic aspects, pathogenesis and therapy of the disease. In C3H/HeJ mice alopecia areata can be experimentally induced by grafting lesional skin from an affected mouse to a histocompatible recipient which offers the possibility to study the influence of various factors on the development of the disease. Studies on the C3H/HeJ mouse and the DEBR have corroborated the concept that alopecia areata is a T-cell mediated autoimmune disease and various steps and aspects of the pathogenesis have been elucidated. Based on this knowledge new therapeutic options may be developed such as inhibition of lymphocyte-homing by an anti-CD44v10 antibody, or inhibition of costimulation by monoclonal antibodies. Therapeutic studies in the C3H/HeJ mouse and the DEBR suggest that alopecia areata can be treated by topical tacrolimus but treatment in humans may only be successful after development of an improved vehicle that facilitates penetration of tacrolimus down to the hair bulb. Current investigations in mice are designed to elucidate the mechanisms how contact sensitizers act in the treatment of alopecia areata, and this will hopefully lead to the development of more specific approaches based on the beneficial effect of contact sensitizers.

The effects of interleukin 10 and interferon gamma cytokine gene polymorphisms on survival after autologous bone marrow transplantation for patients with breast cancer

Several clinical trials evaluating the induction of autoimmune graft-versus-host disease (GVHD) after autologous bone marrow transplantation (BMT) as antitumor immunotherapy have shown that autologous GVHD is associated with increased production of interleukin (IL)-10. The induction of autologous GVHD also segregated with single nucleotide polymorphisms in the IL-10 promoter region (IL-10 -592 and IL-10 -1082 ) and with CA repeats in the first intron of the interferon (IFN)-gamma gene. Polymorphisms within these promoter regions can significantly modify the cytokine response because of differential transcription factor efficiency. This study evaluated the relationship between inheritance of polymorphisms within the IL-10 promoter and in the IFN-gamma gene and the overall survival of patients who received autologous BMT for metastatic breast cancer. Peripheral mononuclear cells from 87 women enrolled in 3 autologous BMT (plus induction of autologous GVHD) clinical trials were examined. By using a Cox proportional hazard model, trends in survival after autologous BMT were analyzed. The model included inheritance polymorphisms of IL-10 -592 , IL-10 -1082 , CA repeats within the first intron of the IFN-gamma gene, estrogen and progesterone receptor status, and stage of disease. Increased survival was significantly associated with patients having the IL-10 -592 promoter allele associated with high IL-10 production (hazard ratio, 0.23; 95% confidence interval, 0.09-0.55; P = .001). The effect of the strong IL-10 promoter allele on survival seems to be independent of the development of clinical autologous GVHD. However, decreased survival was significantly associated with patients having CA repeats associated with higher IFN-gamma transcription (hazard ratio, 2.34; 95% confidence interval, 1.21-4.54; P = .011). Inheritance of specific alleles that modify IL-10 and IFN-gamma production may have unexpected effects on the efficacy of immune-based strategies after autologous BMT. Additional studies are necessary to further define the influence of IL-10 and IFN-gamma on the immune response after BMT.

A model of the ternary complex of interleukin-10 with its soluble receptors

BACKGROUND

Interleukin-10 (IL-10) is a cytokine whose main biological function is to suppress the immune response by induction of a signal(s) leading to inhibition of synthesis of a number of cytokines and their cellular receptors. Signal transduction is initiated upon formation of a ternary complex of IL-10 with two of its receptor chains, IL-10R1 and IL-10R2, expressed on the cell membrane. The affinity of IL-10R1 toward IL-10 is very high, which allowed determination of the crystal structure of IL-10 complexed with the extracellular/soluble domain of IL-10R1, while the affinity of IL-10R2 toward either IL-10 or IL-10/sIL-10R1 complex is quite low. This so far has prevented any attempts to obtain structural information about the ternary complex of IL-10 with its receptor chains.

RESULTS

Structures of the second soluble receptor chain of interleukin-10 (sIL-10R2) and the ternary complex of IL-10/sIL-10R1/sIL-10R2 have been generated by homology modeling, which allowed us to identify residues involved in ligand-receptor and receptor-receptor interactions.

CONCLUSION

The previously experimentally determined structure of the intermediate/binary complex IL-10/sIL-10R1 is the same in the ternary complex. There are two binding sites for the second receptor chain on the surface of the IL-10/sIL-10R1 complex, involving both IL-10 and sIL-10R1. Most of the interactions are hydrophilic in nature, although each interface includes two internal hydrophobic clusters. The distance between C-termini of the receptor chains is 25 A, which is common for known structures of ternary complexes of other cytokines. The structure is likely to represent the biologically active signaling complex of IL-10 with its receptor on the surface of the cell membrane.

Interleukin-10 in viral diseases and cancer: exiting the labyrinth?

Interleukin-10 (IL-10) is unique among cytokines, as it is considered both as a potent immunostimulatory and immunosuppressive factor. This complex biology has been particularly challenging when trying to define the useful or harmful role of IL-10 in chronic viral diseases and cancer. In the present review, we emphasize how these multiple roles define IL-10 as an adaptive molecule, constantly tuning the host response against dangerous and resourceful pathogens.

Functional divergence of antigen-specific T-lymphocyte responses in syngeneic graft-versus-host disease

Administration of cyclosporine after autologous bone marrow transplantation elicits a T-lymphocyte autoaggression syndrome with remarkable similarity to graft-versus-host disease (GVHD). This syndrome, termed syngeneic GVHD (SGVHD), with both acute and chronic phases, is mediated by a restricted repertoire of autoreactive T cells that promiscuously recognize major histocompatibility complex (MHC) class II determinants in association with a peptide from the invariant chain (MHC class II-invariant chain peptide; CLIP). This study evaluated and compared antigen-specific autoreactive T cells during acute and chronic SGVHD ex vivo isolated with a soluble MHC class II immunoglobulin molecular construct. This approach allows for the direct assessment of the functional behavior of the effector T cells without potential modification by in vitro culture. Two major subsets were detected that had overlapping specificity recognizing the MHC class II-binding domain of CLIP but that were differentially dependent on the N- and C-terminal flanking domains of this peptide. The N- and C-terminal subsets were primarily associated with acute and chronic SGVHD, respectively. The cytokine profiles of the CLIP-reactive T cells, however, were most informative and closely correlated with the onset and progression of disease. Levels of type 1 cytokine, particularly interferon-gamma, messenger RNA (mRNA) production, assessed by quantitative polymerase chain reaction, were dominant during acute SGVHD, whereas chronic SGVHD was associated with type 2 cytokine mRNA production. Although there was a dramatic polarization with respect to cytokine production, only subtle changes in antigen specificity could be detected. Unexpectedly, the functional behavior within the antigen-specific effector cell populations is not fixed and seems to change as the disease progresses to the chronic phase. Concordant with the evolution of the effector T-cell response is a differential loss in B7.1 mRNA expression in the N-terminal CLIP-reactive T-cell subset that may reflect the regulation of this autoimmune response. Of additional interest, autoreactive T cells producing interleukin-10 mRNA were detected in both acute and chronic SGVHD, suggesting that this cytokine may play an important but perhaps paradoxical role in both the onset and progression of this experimental autoaggression syndrome.

S-adenosylmethionine (AdoMet) modulates endotoxin stimulated interleukin-10 production in monocytes

IL-10 is produced by a large variety of cells including monocytes, macrophages, B and T lymphocytes, as well as natural killer cells and is an important suppressor for both immunoproliferative and inflammatory responses. IL-10 exerts antifibrotic effects in the liver, and decreased monocyte synthesis of IL-10 is well documented in alcoholic cirrhosis. Intracellular deficiency of S-adenosylmethionine (AdoMet) is a hallmark of toxin-induced liver injury. Although the administration of exogenous AdoMet attenuates this injury, the mechanisms of its actions are not fully established. This study was performed to investigate the effect of exogenous AdoMet on IL-10 production in LPS-stimulated RAW 264.7 cells, a murine macrophage cell line. Our results demonstrated that exogenous AdoMet administration enhanced both protein production and gene expression of IL-10 in RAW 264.7 cells. Ethionine, an inhibitor for methionine adenosyltransferases, inhibited LPS-stimulated IL-10 both at the protein and mRNA levels. Exogenous AdoMet increased the intracellular cAMP concentration as early as 3 h and continued for 24 h after AdoMet treatment; however, the inhibitors for both adenylyl cyclase and PKA did not significantly affect IL-10 production. On the basis of these results, we conclude that AdoMet administration may exert its anti-inflammatory and hepatoprotective effects, at least in part, by enhancing LPS-stimulated IL-10 production.

The complex role of interleukin-10 in autoimmunity

Interleukin-10 (IL-10) is a cytokine that has been tested in different clinical trials based on its ability to down regulate T helper 1-type responses, namely IFN-gamma secretion and activation of monocytes/macrophages. There is also evidence in different animal models, that IL-10 could be useful in controlling Th2-mediated inflammatory processes. However, IL-10 also displays immunostimulatory properties especially on B cells and activated CD8(+)T cells. These seemingly divergent effects may explain the apparent lack of activity or adverse effects observed after IL-10 treatment in several animal models or clinical trials. Nevertheless, the ability of IL-10 to induce the differentiation of a subset of regulatory CD4(+)T cells (Tr1) and the importance of IL-10 for the in vivo function of regulatory T cells tends to support the view of IL-10 as a crucial cytokine in the control of immune responses. In different in vivo models, these cells were shown to inhibit Th1 and Th2-type inflammatory responses through the secretion of IL-10. These Tr1 cells may thus be used in specific cellular therapy in order to deliver IL-10 precisely at the site of inflammation.

Cytokine and chemokine profiles in autologous graft-versus-host disease (GVHD): interleukin 10 and interferon gamma may be critical mediators for the development of autologous GVHD

Administration of the immunosuppressive drug cyclosporine A (CsA) following autologous stem cell transplantation paradoxically elicits a systemic autoimmune syndrome resembling graft-versus-host disease (GVHD). This syndrome, termed autologous GVHD, is associated with autoreactive CD8(+) T cells that recognize major histocompatibility complex (MHC) class II determinants in association with a peptide from the invariant chain. To investigate the potential role of cytokines and chemokines in autologous GVHD, interleukin 2 (IL-2), IL-4, IL-10, interferon gamma (IFN-gamma), and macrophage inflammatory protein-1alpha (MIP-1alpha) gene expression in peripheral blood mononuclear cells (PBMCs) was determined in 36 patients treated with CsA following transplantation and correlated with the induction of cytolytic activity against autologous phytohemagglutinin-stimulated lymphocytes (PHA-blasts) and the breast cancer cell line (T47D). The determination of gene expression by real-time polymerase chain reaction (PCR) revealed that IL-10 mRNA levels by PBMCs in patients with autologous GVHD were 29-fold higher than in healthy individuals. IFN-gamma (4-fold), IL-2 (3-fold), and MIP-1alpha (44-fold) mRNA levels were also increased in GVHD-induced patients compared with healthy individuals. The ability of PBMCs to lyse autologous PHA-blasts and T47D tumor cells exhibited an identical temporal relationship with expression of IL-10 and IFN-gamma during autologous GVHD. Moreover, the susceptibility to autologous GVHD as assessed in 75 patients was significantly associated with the IL-10(-1082) G/G polymorphic alleles, allelic variants in the promoter region that govern IL-10 production. These findings indicate that IL-10 may play an unexpected but critical role in autologous GVHD and could be utilized to enhance a graft-versus-tumor effect after transplantation. Interestingly, polymorphisms in the IL-10 promoter region may also explain differences in the susceptibility of patients to autologous GVHD induction.

IL-10 as a mediator in the HPA axis and brain

Certain functional interactions between the nervous, endocrine, and immune systems are mediated by cytokines. The pro-inflammatory cytokines, interleukin-1 (IL-1) and tumor necrosis factor (TNF) were among the first to be recognized in this regard. A modulator of these cytokines, IL-10, has been shown to have a wide range of activities in the immune system; in this review, we describe its production and actions in the hypothalamic-pituitary-adrenal (HPA) axis. IL-10 is produced in pituitary, hypothalamic, and neural tissues in addition to lymphocytes. IL-10 enhances corticotropin releasing factor (CRF) and corticotropin (ACTH) production in hypothalamic and pituitary tissues, respectively. Further downstream in the HPA axis endogenous IL-10 has the potential to contribute to regulation of glucocorticosteroid production both tonically and following stressors. Our studies and those of others reviewed here indicate that IL-10 may be an important endogenous regulator in HPA axis activity and in CNS pathologies such as multiple sclerosis. Thus, in addition to its more widely recognized role in immunity, IL-10's neuroendocrine activities described here point to its role as an important regulator in communication between the immune and neuroendocrine systems.

Interleukin-10-induced CD8 cell proliferation

Interleukin (IL)-10, a product of T helper 2 (Th2) lymphocytes, has been shown to be an important regulator of lymphoid and myeloid cells, inhibiting mitogen, peptide and alloantigen-induced T-cell proliferation and IL-2 production. The microenvironment at the time of cell activation, notably the presence or absence of cytokines such as IL-10, interferon-gamma (IFN-gamma) and IL-2, is believed to determine the lineage and magnitude of cell-mediated responses. In this study, we show that recombinant human IL-10 (rhIL-10) exerts a dose-dependent inhibitory effect on human peripheral blood mononuclear cells stimulated in vitro, when these cells have not previously been exposed to rhIL-10. Furthermore, incubation of these cells with high doses of rhIL-10, either before or at the time of activation, results in inhibition which is followed several days later by the emergence of a population of CD8 positive cells. This rhIL-10-responsive CD8, positive cell population still emerges even when the cells are washed following incubation with rhIL-10 prior to cell activation. Using purified CD8 populations this was shown to be a direct action of rhIL-10 on CD8 cells and not via CD4 positive cells and monocytes. This finding was only observed when cells were activated with a cross-linking anti-CD3 antibody and not when activated with phorbol-12-mystrate-13-acetate (PMA) and calcium ionophore (CaIon), suggesting that the effect is mediated through cell-surface receptors. Analysis of CD8 positive clones reveal production of Tc2 patterns of cytokines and reduced cell cytotoxicity to allogeneic, natural killer and lymphokine activated cell targets.

Interleukin-10 dose-dependent regulation of CD4+ and CD8+ T cell-mediated graft-versus-host disease

BACKGROUND

Endogenous interleukin (IL)-10 production has been associated with the lack of graft-versus-host disease (GVHD) in human recipients of MHC-disparate donor grafts. Paradoxically, we have shown that the exogenous administration of high doses (30 microg/dose) of IL-10 to murine recipients of MHC-disparate grafts accelerates GVHD lethality.

METHODS

The effects of IL-10 on GVHD mediated by either CD4+ or CD8+ T cells was examined in studies involving exogenous IL-10 administration or the infusion of T cells from IL-10-deficient (-/-) donor mice. The role of interferon (IFN)-gamma on IL-10-induced GVHD acceleration was studied using IFN-gamma-deficient (-/-) donor mice or neutralizing monoclonal antibody.

RESULTS

IL-10 was found to have a dose-dependent effect on the GVHD lethality mediated by either CD4+ or CD8+ T cells. High doses of exogenous IL-10 accelerated GVHD lethality. IFN-gamma release was not responsible for the IL-10 facilitation of GVHD lethality. Paradoxically, low doses of IL-10 protected mice against GVHD lethality. The GVHD protective effect of the bioavailability of small amounts of IL-10 was confirmed by demonstrating that the infusion of T cells from IL-10 -/- donors accelerated GVHD lethality.

CONCLUSIONS

The results suggest that IL-10 has a dose-dependent effect on the GVHD lethality mediated by CD4+ or CD8+ T cells, such that high doses accelerate lethality, while low amounts of bioavailable IL-10 are protective.

Human interleukin-10 expression in T/natural killer-cell lymphomas: association with anaplastic large cell lymphomas and nasal natural killer-cell lymphomas

Several cytokines have been implicated in the pathogenesis of human lymphomas. Among them, interleukin-10 (IL-10) is a pleiotropic cytokine with various biological effects on B and T lymphocytes. Its expression has been essentially studied in B-cell lymphomas, where it appears to act as an autocrine growth factor. BCRF1 (also called viral IL-10), an open reading frame of Epstein-Barr virus, exhibits extensive sequence and functional homologies with human IL-10. Some entities belonging to T- or natural killer (NK)-cell lymphomas are characterized by a frequent association with Epstein-Barr virus. We analyzed 39 cases of peripheral T-cell lymphoma, as well as 7 cases of nasal NK-cell lymphoma, for the presence of IL-10 transcripts by in situ hybridization, to see whether this cytokine was expressed in these tumors and whether its expression could be related to their histological subtype and to the presence of Epstein-Barr virus. Because the riboprobe used for in situ hybridization recognizes both human and viral IL-10, 12 cases were also analyzed by reverse transcription-polymerase chain reaction to verify the human or viral origin of IL-10. It was found that 8 of 11 (73%) anaplastic large cell lymphomas (ALCLs), 2 of 11 (18%) pleomorphic T-cell lymphomas, and 3 of 7 (43%) nasal NK-cell lymphomas exhibited a large number of IL-10-expressing cells, whereas only rare scattered cells were detected in angioimmunoblastic (11 of 11) and in gammadelta T-cell lymphomas (6 of 6). In ALCLs, the pattern of IL-10 mRNA-expressing cells showed an overlapping with the CD30 staining and preferential localization in sinusal and perifollicular areas, thereby suggesting that IL-10-expressing cells were tumor cells. Furthermore, IL-10 transcripts were detected in the SU-DHL-1 anaplastic lymphoma cell line. No correlation with Epstein-Barr virus profile was found, because all cases of ALCL were negative for EBER 1 and 2 genes by in situ hybridization. We confirmed the presence of human IL-10 mRNA by reverse transcription-polymerase chain reaction in ALCLs as well as in NK-cell lymphomas, whereas viral IL-10 was not detected. Thus, human and not viral IL-10 is frequently expressed by tumor cells in ALCLs and nasal NK-cell lymphomas. In view of its function in the proliferation and the differentiation of cytotoxic T and NK cells, and its immunosuppressive properties, IL-10 may have a role in the pathogenesis of these lymphomas.

Mapping of the interleukin-10/interleukin-10 receptor combining site

The discontinuous interleukin-10(IL-10)/interleukin-10 receptor (IL-10R) combining site was mapped using sets of overlapping peptides derived from both binding partners bound to continuous cellulose membranes. Low affinity binding of single regions of the discontinuous contact sites on IL-10 and IL-10R could be identified due to (1) high peptide density on the membrane support, (2) incubation with high protein concentrations, (3) indirect immunodetection of the ligates after electrotransfer onto polyvinylene difluoride membranes, and (4) use of highly overlapping peptide scans of different length (6-mers and 15-mers). The single binding regions identified for each protein species are separated in the protein sequences, but form continuous areas on the surface of IL-10 (X-ray structure) and IL-10R (computer model). Furthermore, four epitopes of neutralizing anti-IL-10 and anti-IL-10R antibodies were mapped and overlap with these binding regions. Soluble peptides (15- to 19-mers) each spanning one of the three identified IL-10-derived receptor binding regions displayed no significant affinity to IL-10R as expected, whereas a peptide (35-mer) comprising two of these regions had considerably higher binding activity. The data are consistent with a previously published computer model of the IL-10/IL-10R complex. This approach should be generally applicable for the mapping of non-linear protein-protein contact sites.

Successful Adoptive Cellular Immunotherapy Is Dependent on Induction of a Host Immune Response Triggered by Cytokine (IFN-γ and Granulocyte/Macrophage Colony-Stimulating Factor) Producing Donor Tumor-Infiltrating Lymphocytes

Adoptive immunotherapy with tumor-infiltrating lymphocytes (TIL) and systemic low dose rIL-2 effectively eradicates pulmonary metastases of the murine MCA-105 sarcoma. We described earlier that host CD8+ T cells are critical for tumor eradication and that successful treatment is associated with production of high levels of IFN-γ and granulocyte/macrophage (GM)-CSF by donor TIL in vitro. Here, we propose the mechanism through which adoptively transferred Thy-1.1+ TIL induce a host antitumor response in congenic Thy-1.2+ tumor-bearing mice. Donor Thy-1.1+ TIL were detected at the tumor site 12 h after transfer. These Thy-1.1+ cells produced IFN-γ and GM-CSF in situ. The percentage of Thy-1.1+ TIL at the tumor site increased up to 16.4 ± 4.9% 24 h after transfer but decreased to undetectable levels thereafter. In contrast, the percentages of host cells producing IFN-γ and GM-CSF continued to increase at the tumor site. These increases were significantly higher in TIL + rIL-2-treated mice compared with untreated mice and rIL-2-treated mice 48 h after TIL transfer. The appearance of IFN-γ+ and GM-CSF+ cells was followed by a large influx of host CD4+, CD8+, and Thy-1.2+ TIL and eventually by tumor eradication. This response was tumor specific since TIL obtained from MCA-205 did not induce high levels of IFN-γ and GM-CSF and did not induce tumor eradication of MCA-105 tumor. Coinjection of Thy-1.1+ TIL and anti-IFN-γ or anti-GM-CSF mAb significantly inhibited antitumor efficacy of the TIL + rIL-2 treatment. We conclude that successful adoptive immunotherapy in this model is mediated through cytokine production by adoptively transferred TIL that induce a host T cell-dependent antitumor response.

Regulation of mouse immuno-responses by a natural suppressor cell clone from bone marrow

Natural suppressor (NS) activity is mediated by several kinds of cell lineages in bone marrow. We demonstrated that a NS cell, clone 7-31, was obtained after limiting dilution with bone marrow culture supplemented with WEHI supernatant. Clone 7-31, was capable of non-specific suppression of the generation of cytotoxic T lymphocytes without major histocompatibility complex restriction. Suppression of cytotoxic thymus-dependent lymphocyte (CTL) generation was also induced with a cell-free supernatant from the 7-31 cells. Interleukin-2 (IL-2) containing concanavallin-A-conditioned medium could not reverse the suppression. The supernatant did not inhibit the proliferation of IL-2-dependent CTLL-2 cells and rapidly growing tumour cells and fibroblasts. Thus, this bone marrow suppressor cell produces a soluble factor that inhibits the generation of CTL in vitro, and prolongs the acceptance of skin allografts in in vivo.

Bidirectional Effect of Interleukin-10 on Early Murine B-Cell Development: Stimulation of flt3-Ligand Plus Interleukin-7–Dependent Generation of CD19− ProB Cells From Uncommitted Bone Marrow Progenitor Cells and Growth Inhibition of CD19+ ProB Cells

B-cell commitment and early development from multipotent hematopoietic progenitor cells has until recently been considered to be dependent on direct interaction with stromal cells. We recently showed that the flt3 ligand (FL) has a unique ability to interact with interleukin-7 (IL-7) to directly and selectively promote B-cell development from murine bone marrow progenitor cells with a combined myeloid and lymphoid potential. Here we report that whereas IL-10 alone has no ability to stimulate growth of primitive (Lin−Sca-1+c-kit+) bone marrow progenitor cells, it potently enhances FL + IL-7–induced proliferation (sevenfold). This enhanced proliferation results from recruitment of progenitors unresponsive to FL + IL-7 alone, as well as from increased growth of individual clones, resulting in a 7,000-fold cellular expansion over 12 days. Single cell cultures and delayed addition studies suggested that the stimulatory effect of IL-10 was directly mediated on the progenitor cells. The cells generated in response to FL + IL-7 + IL-10 appeared to be almost exclusively proB cells, as shown by their expression of B220, CD24, CD43, and lack of expression of cμ, myeloid, erythroid, and T-cell surface antigens. Although IL-10 also enhanced kit ligand (KL) + IL-7–induced proliferation of Lin−Sca-1+c-kit+ progenitor cells, the resulting cells were predominantly myeloid progeny. Accordingly, FL + IL-7 + IL-10 was 100-fold more efficient in stimulating production of proB cells than KL + IL-7 + IL-10. In contrast to its ability to stimulate the earliest phase of proB cell formation and proliferation, IL-10 inhibited growth of proB cells generated in response to FL + IL-7. Analysis of CD19 expression on cells generated in FL + IL-7 + IL-10 showed that almost all cells generated under these conditions lacked expression of CD19, in contrast to cells generated in the absence of IL-10, which were predominantly CD19+. Replating of sorted CD19+ and CD19− proB cells in FL + IL-7 or FL + IL-7 + IL-10 showed that IL-10 efficiently blocked growth of CD19+, but not CD19− cells. Both CD19− and CD19+ cells expressed λ5 and VpreB , shown to be specific for B-cell progenitors. In addition, sorted CD19− cells generated CD19+ cells in response to FL + IL-7. Thus, IL-10 has a dual regulatory effect on early B-cell development from primitive murine bone marrow progenitor cells in that it enhances FL + IL-7–induced proB-cell formation and growth before acquisition of CD19 expression, whereas growth of CD19+ proB cells is inhibited.

Bidirectional Effect of Interleukin-10 on Early Murine B-Cell Development: Stimulation of flt3-Ligand Plus Interleukin-7–Dependent Generation of CD19− ProB Cells From Uncommitted Bone Marrow Progenitor Cells and Growth Inhibition of CD19+ ProB Cells

B-cell commitment and early development from multipotent hematopoietic progenitor cells has until recently been considered to be dependent on direct interaction with stromal cells. We recently showed that the flt3 ligand (FL) has a unique ability to interact with interleukin-7 (IL-7) to directly and selectively promote B-cell development from murine bone marrow progenitor cells with a combined myeloid and lymphoid potential. Here we report that whereas IL-10 alone has no ability to stimulate growth of primitive (Lin−Sca-1+c-kit+) bone marrow progenitor cells, it potently enhances FL + IL-7–induced proliferation (sevenfold). This enhanced proliferation results from recruitment of progenitors unresponsive to FL + IL-7 alone, as well as from increased growth of individual clones, resulting in a 7,000-fold cellular expansion over 12 days. Single cell cultures and delayed addition studies suggested that the stimulatory effect of IL-10 was directly mediated on the progenitor cells. The cells generated in response to FL + IL-7 + IL-10 appeared to be almost exclusively proB cells, as shown by their expression of B220, CD24, CD43, and lack of expression of cμ, myeloid, erythroid, and T-cell surface antigens. Although IL-10 also enhanced kit ligand (KL) + IL-7–induced proliferation of Lin−Sca-1+c-kit+ progenitor cells, the resulting cells were predominantly myeloid progeny. Accordingly, FL + IL-7 + IL-10 was 100-fold more efficient in stimulating production of proB cells than KL + IL-7 + IL-10. In contrast to its ability to stimulate the earliest phase of proB cell formation and proliferation, IL-10 inhibited growth of proB cells generated in response to FL + IL-7. Analysis of CD19 expression on cells generated in FL + IL-7 + IL-10 showed that almost all cells generated under these conditions lacked expression of CD19, in contrast to cells generated in the absence of IL-10, which were predominantly CD19+. Replating of sorted CD19+ and CD19− proB cells in FL + IL-7 or FL + IL-7 + IL-10 showed that IL-10 efficiently blocked growth of CD19+, but not CD19− cells. Both CD19− and CD19+ cells expressed λ5 and VpreB , shown to be specific for B-cell progenitors. In addition, sorted CD19− cells generated CD19+ cells in response to FL + IL-7. Thus, IL-10 has a dual regulatory effect on early B-cell development from primitive murine bone marrow progenitor cells in that it enhances FL + IL-7–induced proB-cell formation and growth before acquisition of CD19 expression, whereas growth of CD19+ proB cells is inhibited.

Identification and functional characterization of a second chain of the interleukin-10 receptor complex

Interleukin-10 (IL-10) is a pleiotropic cytokine which signals through a specific cell surface receptor complex. Only one chain, that for ligand binding (IL-10Ralpha or IL-10R1), was identified previously. We report here that, although human IL-10 binds to the human IL-10R1 chain expressed in hamster cells, it does not induce signal transduction. However, the co-expression of CRFB4, a transmembrane protein of previously unknown function belonging to the class II cytokine receptor family, together with the IL-10R1 chain renders hamster cells sensitive to IL-10. The IL-10:CRFB4 complex was detected by cross-linking to labeled IL-10. In addition, the IL-10R1 chain was able to be co-immunoprecipitated with anti-CRF antibody when peripheral blood mononuclear cells were treated with IL-10. These results demonstrate that the CRFB4 chain is part of the IL-10 receptor signaling complex. Thus, the CRFB4 chain, which we designate as the IL-10R2 or IL-10Rbeta chain, serves as an accessory chain essential for the active IL-10 receptor complex and to initiate IL-10-induced signal transduction events.

Recent advances in graft-versus-host disease (GVHD) prevention

In the 1970s and 1980s, GVHD prevention approaches were limited in number. Recent advances in our understanding of the requirements for T-cell immune responses and for basic mechanism(s) involved in GVHD pathophysiology have led to exciting new strategies for GVHD prevention. This review focuses upon recent developments in GVHD prevention generated over the past 5 years. We have selected five different types of strategies to highlight including: 1) the in vivo targeting of GVHD-reactive T cells using either intact and F(ab')2 fragments of monoclonal antibodies directed against T-cell-surface determinants or immunotoxins which consist of antibodies linked to toxins, 2) a comparison of the in vivo immunosuppressive effects of FK506 and rapamycin on T-cell signaling, 3) the inhibition of T-cell activation through blockade of costimulatory or adhesogenic signals, 4) shifting the balance between acute GVHD-inducing T-helper-type 1 (Th1) T cells to anti-inflammatory T-helper-type 2 (Th2)-type T cells, and 5) the regulation of alloreactive T-cell activation by treatment with peptide analogs which affect either TCR/MHC, CD4/MHC class II, or CD8/MHC class I interactions. Collectively, these approaches are illustratrative of the progress made in extending our GVHD prevention armamentarium.

Resolution of recombinant human interleukin 10 from variants by recycling free flow focusing

Recombinant human interleukin 10 (rhIL-10) is a potential human therapeutic agent for treating inflammatory bowel diseases and rheumatoid arthritis. The rhIL-10 molecule derived from Escherichia coli including bodies consists of two identical subunits forming a noncovalent dimer. Since the ability to separate rhIL-10 from closely related impurities was highly desirable, recycling free flow focusing (RFFF) was utilized for the purification process development of rhIL-10. Under nondenaturing conditions, RFFF was able to separate rhIL-10 from fractions enriched in rhIL-10 variants. Three major monomeric variants (A, B, and C) can be identified and quantitated by reversed phase HPLC. The isoelectric point (pI) of rhIL-10 was empirically determined to be 8.2 while that for the three variant populations were in the range 7.3-7.5. Knowledge of these pI's would potentially facilitate the optimization process for ion-exchange chromatography. Furthermore, the technique provided a mild and fast preparation procedure for obtaining the recombinant protein and its variants for further characterization, as evidenced in the separation of rhIL-1- from variant C by successive RFFF treatments.

Suppression of tumor necrosis factor-alpha production by interleukin-10 is enhanced by cAMP-elevating agents

The pro-inflammatory peptide tumor necrosis factor-alpha (TNF) stimulates production of the anti-inflammatory cytokine-interleukin-10 by monocytes which in turn inhibits the synthesis of TNF. This inhibitory effect of interleukin-10 may contribute to the balance of pro- and anti-inflammatory cytokines in several diseases, e.g., chronic inflammatory bowel disease. In the present study we addressed the question whether interleukin-10 in combination with other TNF-suppressing agents leads to enhanced suppression of TNF synthesis. We investigated the inhibitory potency of interleukin-10 in combination with rolipram, a specific type IV phosphodiesterase inhibitor, or with cicaprost, a stable prostacyclin analogue in lipopolysaccharide-stimulated human peripheral blood mononuclear cells. Peripheral blood mononuclear cells were stimulated with 10 ng/ml lipopolysaccharide in the absence or presence of interleukin-10 or one of the cAMP-elevating agents. First, we confirmed the TNF-suppressing effect of interleukin-10, rolipram and cicaprost alone and determined the IC50 for these substances. Second, for the combination of interleukin-10 with one of the cAMP-elevating substances we were able to demonstrate enhanced TNF inhibition. Of these, the combination of interleukin-10 and rolipram revealed an additive effect. The maximal TNF synthesis of 5.5 +/- 1.1 ng/ml after lipopolysaccharide stimulation alone was inhibited by 0.1 ng/ml interleukin-10 to 2.7 +/- 0.6 ng/ml TNF and by 100 nM rolipram to 3.1 +/- 0.6 ng/ml TNF. Both substances combined suppressed TNF synthesis to 1.5 +/- 0.3 ng/ml. After stimulation with Staphylococcus epidermidis we could demonstrate a more pronounced inhibition of TNF synthesis by interleukin-10 compared to rolipram which was more effective after stimulation with lipopolysaccharide. Finally, the additive inhibitory effect of interleukin-10 and rolipram could be confirmed on the level of TNF mRNA. The results obtained in the present investigation could form a prerequisite to study the combination of interleukin-10 and cAMP-elevating agents in in vivo models of acute or chronic inflammatory diseases.

Crystal structure of human interleukin-10 at 1.6 A resolution and a model of a complex with its soluble receptor

The crystal structure of human interleukin-10 (IL-10) was refined at 1.6 A resolution against X-ray diffraction data collected at 100 K with the use of synchrotron radiation. Although similar to the IL-10 structure determined previously at room temperature, this low-temperature IL-10 structure contains, in addition, four N-terminal residues, three sulfate anions, and 175 extra water molecules. Whereas the main-chain conformation is preserved, about 30% of the side chains, most of them on the protein surface, assume different conformations. A computer model of a complex of IL-10 with its two soluble receptors was generated based on the topological similarity of IL-10 to interferon-gamma. The contact region between the cytokine and each receptor shows excellent complementarity of polar and hydrophobic interactions, suggesting that the model is generally correct and should be useful in guiding mutagenesis experiments.

Evidence suggesting a stimulatory role for interleukin-10 in erythropoiesis in vitro

Interleukin-10 (IL-10) has been shown to exert anti-inflammatory effects by suppressing macrophage proliferation and inhibiting cytokine production. In this study we show that in the presence of erythropoietin (EPO), the addition of IL-10 results in a significant dose-dependent increase in both Burst Forming Unit-Erythroid (BFU-E) and Colony Forming Unit-Erythroid (CFU-E) colony growth in both serum-containing and serum-free murine cultures in vitro. IL-10 acts at the later stages of erythroid cell proliferation and differentiation as the increase in colony number was greater in CFU-E than in BFU-E, and was similar when IL-10 was added to BFU-E cultures at the time of culture initiation as when its addition to culture was delayed for 7 days. Furthermore, no increase in BFU-E colony number was noted when IL-10, added at the time of culture initiation, was neutralized by the addition to culture of a monoclonal anti-IL-10 antibody up to 7 days later. The increases in BFU-E by IL-10 addition were not the result of prolongation of BFU-E colony lifespan, which was not significantly different in IL-10 treated and control cultures, respectively. Rather IL-10 stimulated the proliferation of erythroid clusters that were now large enough to be recognized as colonies. IL-10-induced stimulation of erythropoiesis appeared to be independent of its inhibitory effects on macrophage function, as stimulation of erythroid colony growth was similar in macrophage-containing and depleted cultures. Studies to determine if the IL-10 effect was direct or indirect yielded equivocal results. A limiting dilution assay suggested a direct effect. However, a log/log dose response curve with IL-10 did not pass through the origin suggesting an indirect effect. These studies indicate that IL-10 acts synergistically with EPO to significantly increase stimulation of erythroid differentiation and proliferation in vitro and may be involved in the regulation of normal erythropoiesis in vivo.

Peritoneal cavity CD5 (Bla) B cells: cytokine induced IgA secretion and homing to intestinal lamina propria in SCID mice

The mouse peritoneal cavity contains a unique population of B cells (Bla) with a high IgM/low IgD ratio, CD5+ (Ly1), MAC-1 + phenotype. These cells arise early in ontogeny, utilize a limited repertoire of immunoglobulin V genes, produce polyreactive IgM antibodies and have been implicated as the source of many auto-reactive immunoglobulins. Recent data from chimeric mice suggest that this B cell population also contains the precursors of many IgA plasma cells found in the lamina propria of the small intestine. In the present study we have investigated the potential of this cell population to secrete IgA (and IgG) in response to various cytokines. IL-5 alone, or in combination with IL-2, greatly enhanced secretion of both IgG and IgA. Cytokine-induced IgA secretion resulted from expansion of a subset of CD5 B cells co-expressing sIgA. Adoptive transfer of CD5 B cells while peripheral lymph nodes contained only IgM+ and some IgG+ B cells. Transfer of CD5+ B cells also reconstituted serum IgM, IgG and IgA and IgG, immunoglobulins characteristic of mucosal and anamnestic responses, when cultured in vitro with the appropriate cytokines. These cells also give rise to IgA plasma cells in the intestinal lamina propria following adoptive transfer to SCID mice, further supporting the hypothesis that cells of this lineage may be important in immune responses at mucosal surfaces.

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.

Crystallization and preliminary X-ray investigation of recombinant human interleukin 10

Crystals of recombinant human interleukin 10 have been grown from solutions of ammonium sulfate. The crystals are tetragonal, space group P4(1)2(1)2 or P4(3)2(1)2; the unit cell axes are a = 36.5 A and c = 221.9 A. There is the equivalent of one polypeptide chain in the asymmetric unit. The crystals are stable to X-rays and diffract to at least 2.5 A resolution.

Characterization of recombinant extracellular domain of human interleukin-10 receptor

The extracellular region of the human interleukin-10 (hIL-10) receptor was expressed using a myeloma cell line and was purified to homogeneity by ligand-affinity chromatography. SDS-polyacrylamide gel electrophoresis analysis indicated that the soluble receptor is glycosylated and has an apparent molecular mass of 35,000-45,000. Under native conditions, soluble hIL-10 receptor was determined by gel filtration to be a monomeric protein. Soluble hIL-10 receptor was able to inhibit the binding of 125I-hIL-10 to the full-length receptor and was able to antagonize the effect of human IL-10 in cell proliferation and cytokine synthesis inhibition. The apparent dissociation constant (Kd) of soluble hIL-10 receptor was determined to be 563 +/- 59 pM, approximately 2- to 10-fold higher than that found on intact cells (Tan, J. C., Indelicato, S. R., Narula, S. K., Zavodny, P. J., and Chou, C.-C. (1993) J. Biol. Chem. 268, 21053-21059; Liu, Y., Wei, S. H.-Y., Ho, A. S.-Y., de Waal Malefyt, R., and Moore, K. W. (1994) J. Immunol. 152, 1821-1829). When hIL-10 binds soluble hIL-10 receptor in solution, a single complex was detected by gel filtration, and the complex was found to consist of two hIL-10 dimers and four soluble receptor monomers, suggesting that hIL-10 may induce a novel mode of oligomerization of the receptor upon binding.

Studies on the T cell dependence of natural IgM and IgG antibody repertoires in adult mice

The present experiments address the thymic dependence of IgM and IgG natural antibody repertoires in adult euthymic and athymic BALB/c mice, as well as in athymic animals reconstituted with a fixed number of syngeneic T cells. Within 3 weeks of the transfer of 10(7) syngeneic splenic T lymphocytes to athymic mice, the T cell compartment is essentially reconstituted in the peritoneal cavity (up to 80% of the numbers in euthymic animals), but is only 10-20% of controls in the spleen and lymph nodes. Early after transfer, there is an increase in the numbers of activated B cells and of immunoglobulin-secreting cells in the spleen, and within 1-2 weeks, the serum concentrations of IgG1 and IgG2a are fully reconstituted to control levels (30-40-fold increased). Multiparametric analyses of serum IgM and IgG repertoires revealed that euthymic and athymic mice share essentially all natural antibody reactivities towards syngeneic extracts of liver and muscle. When tested at the same immunoglobulin concentrations, however, nude sera consistently show higher values of reactivity in all detectable bands. The transfer of 10(7) splenic T cells into athymic mice results in a general decrease of serum IgM reactivities, some of which become undetectable, and in alterations of the serum IgG repertoire as early as 1 week, and for at least 4 weeks after transfer. T cell transfer, however, fails to restore the euthymic IgM and IgG repertoires within 4 weeks. The present observations demonstrate that, after limited T cell reconstitution of nude mice, there is a rapid and quantitatively important increase of serum IgG1 and IgG2a production; the serum IgM reactivity repertoire is qualitatively similar in euthymic and athymic animals, but is generally decreased by T cell activity; and the serum IgG repertoire, which is qualitatively similar in euthymic and athymic animals, is amplified by T cell activity and partially altered by T cell transfer into athymic animals. These results raise questions on the mechanisms of B cell activation and natural antibody repertoire selection in T cell-deficient adult individuals.

Cloning and expression of a cDNA encoding ovine interleukin 7

Using the polymerase chain reaction (PCR) and primers based on regions of homology between the human and murine interleukin 7 (IL-7)-encoding cDNAs, we have amplified an ovine (ov) IL-7 cDNA from reverse-transcribed RNA extracted from concanavalin A (Con A)-activated ovine lymph-node cells. The nucleotide sequence of the cDNA and the predicted amino acid (aa) sequence showed significant homology to those of the human and murine molecules. The ovIL-7 cDNA encodes a 176-aa polypeptide that, based on analysis of murine IL-7, is processed to a protein of 151 aa. The cDNA was demonstrated to encode a protein with IL-7 biological activity. Supernatants from COS or CHO-K1 cells transfected with an expression vector containing the ovIL-7 cDNA were able to synergise with a suboptimal level of Con A to induce proliferation of ovine thymocytes. In addition, both supernatants were able to induce thymocyte proliferation, albeit at a reduced level, in the absence of Con A. Further experiments demonstrated that for induction of ovine thymocyte proliferation, recombinant (re)-ovIL-7 was able to synergise with re-human (h) IL-2 but not re-hIL-6 or tumor necrosis factor-alpha (re-hTNF alpha).

Molecular characterization and determination of the coding capacity of the genome of equine herpesvirus type 2 between the genome coordinates 0.235 and 0.258 (the EcoRI DNA fragment N; 4.2 kbp)

The complete DNA nucleotide sequence of the EcoRI DNA fragment N (0.235 to 0.258 viral map units) of equine herpes virus type 2 (EHV-2) strain T400/3 was determined. This DNA fragment comprises 4237 bp with a base composition of 55.23% G+C and 44.77% A+T. Nineteen open reading frames (ORFs) of 50-287 amino acid (aa) residues were detected. ORF number 10 is located between the nucleotide position 2220 and 2756 coding for a protein of 179 amino acid residues. This protein shows significant homology to the cytokine synthesis inhibitory factor (CSIF; interleukin 10) of human (76.4%) and mouse (68.5%), and to the Epstein-Barr virus (EBV) protein BCRF1 (70.6%). The existence of an interleukin 10 (IL-10) analogous gene within the genome of the EHV-2 was confirmed by screening the genome of nine EHV-2 strains using specific oligonucleotide primers corresponding to the 5' and 3' region of this particular gene by polymerase chain reaction. In all experiments an 870 bp DNA product was amplified. The specifity of the amplified DNA fragments obtained from individual EHV-2 strains was confirmed by DNA-DNA hybridization experiments. The DNA sequence analysis of the amplified DNA products of the EHV-2 strain LK was carried out. This analysis revealed the identity of the corresponding IL-10 gene (540 bp) of this strain to the IL-10 gene of EHV-2 strain T400/3. The presented data indicate that the EHV-2 genome harbors a viral interleukin 10-like gene. This is further evidence that the IL-10 gene can be present in the genomes of members of the Herpesviridae family.

In vivo effects of interleukin-10 on contact hypersensitivity and delayed-type hypersensitivity reactions

Interleukin (IL) 10 is a recently discovered cytokine, originally isolated from T-helper 2 (Th2) cells, which inhibits cytokine production of T-helper 1 (Th1) cells. Because Th1 cells appear to be of importance during the contact hypersensitivity reaction (CHS) we hypothesized that IL-10 might modulate the outcome of CHS in vivo. Intraperitoneal injection of murine recombinant IL-10 (1000 ng) into naive mice 24, 72, or 120 h before sensitization by epicutaneous application of 2,4-dinitrofluorobenzene (DNFB) did not affect ear swelling when ears were challenged 5 d later. However, intraperitoneal injection of IL-10 into already sensitized mice 24 h before challenge resulted in a significant suppression of the ear swelling response, suggesting that under the conditions employed IL-10 is able to block the effector phase, but not the induction phase of CHS in vivo. The suppression could be reversed by the concurrent injection of an IL-10 antibody. Moreover, heat inactivation of native IL-10 resulted in loss of the inhibitory capacity. When mice were sensitized by subcutaneous injection of trinitrophenyl-coupled spleen cells (DTH) instead of epicutaneous application of the hapten (CHS), intraperitoneally-injected IL-10 suppressed the effector phase, but also the induction phase of DTH. IL-10 did not inhibit the toxic ear-swelling response induced by topical application of two irritants tested (croton oil or benzalkonium chloride). The capacity of IL-10 to suppress the effector phase of CHS and DTH supports an important role for this cytokine in the downregulation of type IV immune reactions in vivo. The finding that IL-10 suppresses the induction of DTH, but not of CHS, further suggests that CHS and DTH are related but distinct immune reactions.

Human B cell interleukin 10

Interleukin 10 (IL-10) is a novel lymphokine which exhibits strong DNA and amino acid sequence homology to BCRF1, an open reading frame in the Epstein-Barr virus genome. Using a wide panel of EBV positive and EBV negative cell lines, it has been shown that EBV positive B cell lines derived from patients with AIDS and Burkitt's lymphoma (AABCL) secrete large quantities of B cell IL-10, compared with EBV-positive B cell lines obtained from patients with undifferentiated lymphomas of Burkitt's and non-Burkitt's types. In contrast, EBV-negative B cell lines do not express IL-10 by Northern blot analysis, ELISA or even PCR. B cell IL-10 is confined to a narrow window in the B cell differentiation pathway, and whereas IL-10 expression is detected in mature and preplasmacytic stages, none of the pro-B, pre-B, or myeloma cell lines produce IL-10. EBV exerts direct effect on the production of B cell IL-10, and purified tonsillar B cells infected with EBV were triggered to secrete IL-10. The large amount of IL-10 secreted by B cells derived from AIDS-related lymphomas suggests that HIV-1 also exerts direct effect on IL-10 secretion. B cell IL-10 may function as autocrine growth factor for B cell lymphomas, and both IL-10 and BCRF1 seem to be involved in the pathophysiology of non-Hodgkin's lymphomas.

Similar frequencies and kinetics of cytokine producing cells in murine peripheral blood and spleen. Cytokine detection by immunoassay and intracellular immunostaining

Production of IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IFN-gamma, GM-CSF (granulocyte-macrophage colony stimulating factor) and macrophage colony stimulating factor by murine peripheral blood and spleen cells was analyzed following primary and secondary mitogen stimulation in vitro. Individual cytokine producing cells were detected by an intracytoplasmic staining technique. Cytokine production in cells from peripheral blood and spleen was comparable and more rapidly induced by calcium ionophore and phorbol 12-myristate 13-acetate than by concanavaling A. Restimulation in vitro induced both a swift production of cytokines and, for some cytokines, higher frequencies of producing cells. This was especially evident for IL-10 secreting cells, which increased 30-80 times in secondary responses. These analyses using the dual approaches of immunoenzymetric and fluorescent immunohistochemical techniques provide important evidence that cytokine induction kinetics can differ following primary or secondary stimulation.

A receptor for interleukin 10 is related to interferon receptors

We isolated cDNAs encoding a mouse interleukin 10 receptor (mIL-10R) from mouse mast cell and macrophage cell lines. The two cDNAs are substantially identical and express an approximately 110-kDa polypeptide in COS7 cells, which binds mIL-10 specifically. A mouse pro-B-cell line (Ba/F3) expressing transfected recombinant mIL-10R binds IL-10 with high affinity (approximately 70 pM) and proliferates in response to mIL-10. mIL-10R is structurally related to interferon receptors (IFNRs). Since IL-10 inhibits macrophage activation by IFN-gamma, a possible implication of this relationship interaction of IL-10R and IFN-gamma R or their signaling pathways.

Reciprocal cytokine-mediated cellular interactions in mouse epidermis: promotion of gamma delta T-cell growth by IL-7 and TNF alpha and inhibition of keratinocyte growth by gamma IFN

A unique subset of gamma delta T cells, termed dendritic epidermal T cells (DETC), resides in symbiosis with keratinocytes in mouse epidermis. We have shown previously that interleukin 7 (IL-7) which is produced by keratinocytes, promotes growth and prevents apoptosis in DETC. To extend this observation, we examined 12 cytokines, each of which is expressed by epidermal cells at mRNA and/or protein levels, for their capacities to modulate the growth of DETC. Cytokines examined included IL-1 alpha, IL-2, IL-3, IL-4, IL-6, IL-7, IL-8, IL-10, tumor necrosis factor-alpha (TNF alpha), interferon-gamma (IFN gamma), granulocyte/macrophage-colony stimulating factor (GM-CSF), and macrophage inflammatory protein-1 alpha (MIP-1 alpha). When tested individually, IL-2 and IL-7 promoted maximal growth of the long-term cultured DETC line 7-17. When tested in combinations, synergistic growth-promoting effects were seen with IL-2 and IL-4 or IL-7, and with IL-7 and IL-4 or TNF alpha. Dose-response experiments demonstrated that TNF alpha, which is produced by keratinocytes, enhances IL-7-induced DETC proliferation, but inhibits IL-2-induced proliferation. The mouse keratinocyte-derived cell line Pam 212 was used to test these cytokines for their capacities to regulate keratinocyte growth. Only gamma IFN, which is produced by DETC, inhibited proliferation in a dose-dependent fashion. These results illustrate three reciprocal pathways by which epidermal cytokines regulate the growth of epidermal cells: 1) a paracrine mechanism by which keratinocyte-derived cytokines (e.g., IL-7 and TNF alpha) promote the growth of DETC, 2) an autocrine mechanism by which DETC-derived cytokines (e.g., IL-2 and IL-4) support their own growth, and 3) a reciprocal pathway in which a cytokine produced by resident epidermal leukocytes (e.g., gamma IFN) modulates the growth of keratinocytes.

Epstein-Barr virus transformation induces B lymphocytes to produce human interleukin 10

Interleukin 10 (IL-10) is a pleiotropic factor that enhances proliferation of activated human B lymphocytes and induces them to secrete high amounts of immunoglobulins. Here we show that several human B cell lines were able to constitutively secrete human (h)IL-10. Whereas none of the pre-B nor the plasmocytic cell lines tested produced hIL-10, 25 of the 36 tested mature B cell lines (lymphoblastoid and Burkitt lymphoma cell lines) secreted hIL-10. Moreover, 24 of these 25 hIL-10-producing B cell lines contained the Epstein-Barr virus (EBV) genome, suggesting a relationship between hIL-10 production by human B cell lines and EBV expression. Accordingly, whereas polyclonal activation via triggering of surface immunoglobulins or CD40 antigen induced highly purified normal human B lymphocytes to produce only low (0.3-0.4 ng/ml) but significant amounts of hIL-10, EBV infection induced them to secrete high amounts of hIL-10 (4-9 ng/ml). Furthermore, addition of exogenous hIL-10, simultaneously to EBV infection, potentiated cell proliferation, whereas a blocking anti-IL-10 antiserum inhibited it. Thus, hIL-10 produced by infected human B lymphocytes appears to be involved in the mechanisms of EBV-induced B cell proliferation.

The genome of equine herpesvirus type 2 harbors an interleukin 10 (IL10)-like gene

A gene was identified within the DNA sequences of the EcoRI DNA fragment N (4.3 kbp) of the genome of equine herpesvirus type 2 (EHV-2) coding for a protein (179 amino acid residues) homologous to the cytokine synthesis inhibitory factor (CSIF; interleukin 10) of the human and mouse, and to the Epstein-Barr virus (EBV) protein BCRF1. This finding is further significant evidence that the interleukin 10 (IL-10) and/or IL-10-like gene can indeed be present in the genomes of members of the herpesviral family.