Modelling asthma in macaques: longitudinal changes in cellular and molecular markers.

The aim of the present study was to determine whether systemic sensitisation and chronic aeroallergen challenge in macaques replicate the classical and emerging immunology and molecular pathology of human asthma. Macaques were immunised and periodically challenged over 2 yrs with house dust mite allergen. At key time-points, serum, bronchoalveolar lavage (BAL) and bronchial biopsies were assayed for genes, proteins and lymphocyte subpopulations relevant to clinical asthma. Immunisation and periodic airway challenge induced changes in immunoglobulin E, airway physiology and eosinophilia consistent with chronic, dual-phase asthma. Sensitisation increased interleukin (IL)-1ß and -6 concentrations in serum, and IL-13 expression in BAL cells. Airway challenge increased: early expression of IL-5, -6, -13 and -19, and eotaxin; and variable late-phase expression of IL-4, -5 and -13, and thymus- and activation-regulated chemokine in BAL cells. CD4+ lymphocytes comprised 30% of the CD3+ cells in BAL, increasing to 50% in the late phase. Natural killer T-cells represented <3% of the CD3+ cells. Corticosteroid treatment reduced serum histamine levels, percentage of CD4+ cells and monocyte-derived chemokine expression, while increasing CD3+ and CD8+ cells in BAL. Sensitisation and periodic aeroallergen challenge of cynomolgus macaques results in physiological, cellular, molecular and protein phenotypes, and therapeutic responses observed in human asthma, providing a model system useful in target and biomarker discovery, and translational asthma research.

Interleukin 10(IL-10) inhibits cytokine synthesis by human monocytes: an autoregulatory role of IL-10 produced by monocytes.

In the present study we demonstrate that human monocytes activated by lipopolysaccharides (LPS) were able to produce high levels of interleukin 10 (IL-10), previously designated cytokine synthesis inhibitory factor (CSIF), in a dose dependent fashion. IL-10 was detectable 7 h after activation of the monocytes and maximal levels of IL-10 production were observed after 24-48 h. These kinetics indicated that the production of IL-10 by human monocytes was relatively late as compared to the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF alpha), and granulocyte colony-stimulating factor (G-CSF), which were all secreted at high levels 4-8 h after activation. The production of IL-10 by LPS activated monocytes was, similar to that of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF, inhibited by IL-4. Furthermore we demonstrate here that IL-10, added to monocytes, activated by interferon gamma (IFN-gamma), LPS, or combinations of LPS and IFN-gamma at the onset of the cultures, strongly inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF at the transcriptional level. Viral-IL-10, which has similar biological activities on human cells, also inhibited the production of TNF alpha and GM-CSF by monocytes following LPS activation. Activation of monocytes by LPS in the presence of neutralizing anti-IL-10 monoclonal antibodies resulted in the production of higher amounts of cytokines relative to LPS treatment alone, indicating that endogenously produced IL-10 inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF. In addition, IL-10 had autoregulatory effects since it strongly inhibited IL-10 mRNA synthesis in LPS activated monocytes. Furthermore, endogenously produced IL-10 was found to be responsible for the reduction in class II major histocompatibility complex (MHC) expression following activation of monocytes with LPS. Taken together our results indicate that IL-10 has important regulatory effects on immunological and inflammatory responses because of its capacity to downregulate class II MHC expression and to inhibit the production of proinflammatory cytokines by monocytes.

Interleukin 10 (IL-10) and viral IL-10 strongly reduce antigen-specific human T cell proliferation by diminishing the antigen-presenting capacity of monocytes via downregulation of class II major histocompatibility complex expression.

Interleukin 10 (IL-10) and viral IL-10 (v-IL-10) strongly reduced antigen-specific proliferation of human T cells and CD4+ T cell clones when monocytes were used as antigen-presenting cells. In contrast, IL-10 and v-IL-10 did not affect the proliferative responses to antigens presented by autologous Epstein-Barr virus-lymphoblastoid cell line (EBV-LCL). Inhibition of antigen-specific T cell responses was associated with downregulation of constitutive, as well as interferon gamma- or IL-4-induced, class II MHC expression on monocytes by IL-10 and v-IL-10, resulting in the reduction in antigen-presenting capacity of these cells. In contrast, IL-10 and v-IL-10 had no effect on class II major histocompatibility complex (MHC) expression on EBV-LCL. The reduced antigen-presenting capacity of monocytes correlated with a decreased capacity to mobilize intracellular Ca2+ in the responder T cell clones. The diminished antigen-presenting capacities of monocytes were not due to inhibitory effects of IL-10 and v-IL-10 on antigen processing, since the proliferative T cell responses to antigenic peptides, which did not require processing, were equally well inhibited. Furthermore, the inhibitory effects of IL-10 and v-IL-10 on antigen-specific proliferative T cell responses could not be neutralized by exogenous IL-2 or IL-4. Although IL-10 and v-IL-10 suppressed IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 production by monocytes, it was excluded that these cytokines played a role in antigen-specific T cell proliferation, since normal antigen-specific responses were observed in the presence of neutralizing anti-IL-1, -IL-6, and -TNF-alpha mAbs. Furthermore, addition of saturating concentrations of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha to the cultures had no effect on the reduced proliferative T cell responses in the presence of IL-10, or v-IL-10. Collectively, our data indicate that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.

High levels of interleukin 10 production in vivo are associated with tolerance in SCID patients transplanted with HLA mismatched hematopoietic stem cells.

Transplantation of HLA mismatched hematopoietic stem cells in patients with severe combined immunodeficiency (SCID) can result in a selective engraftment of T cells of donor origin with complete immunologic reconstitution and in vivo tolerance. The latter may occur in the absence of clonal deletion of donor T lymphocytes able to recognize the host HLA antigens. The activity of these host-reactive T cells is suppressed in vivo, since no graft-vs. -host disease is observed in these human chimeras. Here it is shown that the CD4+ host-reactive T cell clones isolated from a SCID patient transplanted with fetal liver stem cells produce unusually high quantities of interleukin 10 (IL-10) and very low amounts of IL-2 after antigen-specific stimulation in vitro. The specific proliferative responses of the host-reactive T cell clones were considerably enhanced in the presence of neutralizing concentrations of an anti-IL-10 monoclonal antibody, suggesting that high levels of endogenous IL-10 suppress the activity of these cells. These in vitro data correlate with observations made in vivo. Semi-quantitative polymerase chain reaction analysis carried out on freshly isolated peripheral blood mononuclear cells (PBMC) of the patient indicated that the levels of IL-10 messenger RNA (mRNA) expression were strongly enhanced, whereas IL-2 mRNA expression was much lower than that in PBMC of healthy donors. In vivo IL-10 mRNA expression was not only high in the T cells, but also in the non-T cell fraction, indicating that host cells also contributed to the high levels of IL-10 in vivo. Patient-derived monocytes were found to be major IL-10 producers. Although no circulating IL-10 could be detected, freshly isolated monocytes of the patient showed a reduced expression of class II HLA antigens. However, their capacity to stimulate T cells of normal donors in primary mixed lymphocyte cultures was within the normal range. Interestingly, similar high in vivo IL-10 mRNA expressions in the T and non-T cell compartment were also observed in three SCID patients transplanted with fetal liver stem cells and in four SCID patients transplanted with T cell-depleted haploidentical bone marrow stem cells. Taken together, these data indicate that high endogenous IL-10 production is a general phenomenon in SCID patients in whom allogenic stem cell transplantation results in immunologic reconstitution and induction of tolerance. Both donor T cells and host accessory cells contribute to these high levels of IL-10, which would suppress the activity of host-reactive T cell in vivo.

An interleukin 4 (IL-4) mutant protein inhibits both IL-4 or IL-13-induced human immunoglobulin G4 (IgG4) and IgE synthesis and B cell proliferation: support for a common component shared by IL-4 and IL-13 receptors.

Interleukin 4 (IL-4) and IL-13 share many biological functions. Both cytokines promote growth of activated human B cells and induce naive human surface immunoglobulin D+ (sIgD+) B cells to produce IgG4 and IgE. Here we show that a mutant form of human IL-4, in which the tyrosine residue at position 124 is replaced by aspartic acid (hIL-4.Y124D), specifically blocks IL-4 and IL-13-induced proliferation of B cells costimulated by anti-CD40 mAbs in a dose-dependent fashion. A mouse mutant IL-4 protein (mIL-4.Y119D), which antagonizes the biological activity of mouse IL-4, was ineffective. In addition, hIL-4.Y124D, at concentrations of up to 40 nM, did not affect IL-2-induced B cell proliferation. hIL-4.Y124D did not have detectable agonistic activity in these B cell proliferation assays. Interestingly, hIL-4.Y124D also strongly inhibited both IL-4 or IL-13-induced IgG4 and IgE synthesis in cultures of peripheral blood mononuclear cells, or highly purified sIgD+ B cells cultured in the presence of anti-CD40 mAbs. IL-4 and IL-13-induced IgE responses were inhibited > 95% at a approximately 50- or approximately 20-fold excess of hIL-4.Y124D, respectively, despite the fact that the IL-4 mutant protein had a weak agonistic activity. This agonistic activity was 1.6 +/- 1.9% (n = 4) of the maximal IgE responses induced by saturating concentrations of IL-4. Taken together, these data indicate that there are commonalities between the IL-4 and IL-13 receptor. In addition, since hIL-4.Y124D inhibited both IL-4 and IL-13-induced IgE synthesis, it is likely that antagonistic mutant IL-4 proteins may have potential clinical use in the treatment of IgE-mediated allergic diseases.

Early production of thymic stromal lymphopoietin precedes infiltration of dendritic cells expressing its receptor in allergen-induced late phase cutaneous responses in atopic subjects.

BACKGROUND: Thymic stromal lymphopoietin (TSLP) is an interleukin (IL)-7-like cytokine that triggers dendritic cell-mediated T helper (Th)2 inflammatory responses through a receptor consisting of a heterodimer of the IL-7 receptor alpha (IL-7Ralpha) chain and the TSLP receptor (TSLPR), which resembles the cytokine receptor common gamma chain. Dendritic cells activated by TSLP prime development of CD4(+) T cells into Th2 cells contributing to the pathogenesis of allergic inflammation. We hypothesized that allergen exposure induces expression of TSLP and results in recruitment of TSLPR bearing cells in the cutaneous allergen-induced late-phase reaction (LPR) in atopic subjects. METHODS: Skin biopsies were obtained from atopic subjects (n = 9) at various times after cutaneous allergen challenge. In situ hybridization and immunohistochemistry were used to determine TSLP mRNA expression and to measure infiltration of TSLPR(+) DC in skin LPR. RT-PCR and flow cytometry were employed to analyse TSLPR expression on isolated blood DC. RESULTS: Allergen-induced skin TSLP expression occurred as early as 1 h after allergen challenge, whereas TSLPR(+) and CD11c(+) cells infiltrated relatively late (24-48 h). The majority of TSLPR(+) cells were DC co-expressing blood DC antigen-1 (BDCA-1) or BDCA-2. Freshly isolated blood DC expressed both TSLPR and IL-7Ralpha chains. Maturation and stimulation with TSLP or polyriboinosinic-polyribocytidylic acid in vitro upregulated the expression of both TSLPR and IL-7Ralpha chains in DC but not in chemoattractant receptor-homologous molecule expressed on Th2 cells(+) CD4(+) T cells. CONCLUSION: The data suggest that TSLP plays a role in augmenting, through DC recruitment and activation, the development of Th2-type T cells in allergic inflammation.

Interleukin 10 inhibits transforming growth factor-beta (TGF-beta) synthesis required for osteogenic commitment of mouse bone marrow cells.

Interleukin 10 (IL-10) suppressed TGF-beta synthesis in mouse bone marrow cultures. Coincidingly, IL-10 down-regulated the production of bone proteins including alkaline phosphatase (ALP), collagen and osteocalcin, and the formation of mineralized extracellular matrix. The mAb 1D11.16 which neutralizes TGF-beta 1 and TGF-beta 2, induced suppressive effects comparable to IL-10 when administered before the increase of cell proliferation in the culture. It appears that mainly TGF-beta 1 plays a role in this system since (a) TGF-beta 2 levels were undetectable in supernatants from osteogenic cultures, (b) no effect was observed when the anti-TGF-beta 2 neutralizing mAb 4C7.11 was added and (c) the suppressive effect of IL-10 could be reversed by adding exogenous TGF-beta 1. It is unlikely that TGF-beta 1 modulates osteogenic differentiation by changing the proliferative potential of marrow cells since 1D11.16 did not affect [3H]thymidine ([3H]TdR) incorporation or the number of fibroblast colony forming cells (CFU-F) which harbor the osteoprogenitor cell population. Furthermore, 1D11.16 did not alter [3H]TdR uptake by the cloned osteoprogenitor cell lines MN7 and MC3T3. Light and scanning electron microscopy showed that IL-10 and 1D11.16 induced comparable morphological changes in the marrow cultures. Control cultures contained flat adherent cells embedded in a mineralized matrix. In contrast, IL-10 and 1D11.16 treated cultures were characterized by round non-adherent cells and the absence of a mineralized matrix. In this study, the mechanism by which IL-10 suppresses the osteogenic differentiation of mouse bone marrow was identified as inhibition of TGF-beta 1 production which is essential for osteogenic commitment of bone marrow cells.

Reciprocal control of T helper cell and dendritic cell differentiation.

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.

Expression of interleukin-10 activity by Epstein-Barr virus protein BCRF1.

Cytokine synthesis inhibitory factor (CSIF; interleukin-10), a product of mouse TH2 T cell clones that inhibits synthesis of cytokines by mouse TH1 T cell clones, exhibits extensive sequence similarity to an uncharacterized open reading frame in the Epstein-Barr virus BCRF1. Recombinant BCRF1 protein mimics the activity of interleukin-10, suggesting that BCRF1 may have a role in the interaction of the virus with the host's immune system.

Interleukin-10.

Despite the short history of interleukin-10, accumulated evidence indicates that this interleukin plays a major role in suppressing immune and inflammatory responses. Yet interleukin-10 also maintains cell viability and acts as a cofactor to promote the growth of lymphoid and myeloid cells in vitro. Here we review the present knowledge on the structure and function of interleukin-10.

Interleukin-17 and interferon-gamma synergize in the enhancement of proinflammatory cytokine production by human keratinocytes.

Keratinocytes are influenced by cytokines released by skin-infiltrating T lymphocytes. IL-17 is produced by activated CD4+ T cells and can stimulate epithelial cells. We investigated whether IL-17 could modulate the cytokine production and cell-surface molecule expression of keratinocytes. The effects of IL-17 were compared with those of IFN-gamma, which is also derived from activated T cells and is a strong stimulator for keratinocytes. IL-17 enhanced the mRNA and protein production of the proinflammatory cytokines IL-6 and IL-8 in a concentration-dependent way, and induced a weak expression of intercellular adhesion molecule (ICAM)-1 and HLA-DR. The production of IL-1alpha and IL-15 was not altered. IFN-gamma augmented the production of IL-6, IL-8, and IL-15 and strongly induced both cell-surface molecules. IL-17 and IFN-gamma showed marked synergism in the stimulation of IL-6 and IL-8 protein secretion and, to a lesser extent, in the induction of ICAM-1 and HLA-DR expression. The majority of the CD4+ and CD8+ T cell clones derived from lesional psoriatic skin expressed IL-17 mRNA, suggesting that skin-infiltrating T cells can produce this cytokine. This IL-17 mRNA expression was detectable in T helper cell type 1 and type 2 and did not correlate with the IFN-gamma or IL-4 production. In addition, IL-17 mRNA is detectable in biopsies from lesional psoriatic skin, but not in nonlesional control biopsies. Our study indicates that IL-17 is a proinflammatory cytokine, which could amplify the development of cutaneous inflammation and may support the maintenance of chronic dermatoses, through stimulation of keratinocytes to augment their secretion of proinflammatory cytokines.

The role of type I interferons in the differentiation and function of Th1 and Th2 cells.

T-helper cells are compartmentalized according to the cytokines they are able to produce. T-helper 1 cells produce interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), and develop following priming with IL-12. T-helper 2 cells produce IL-4, IL-5, and IL-10, and IL-4 is necessary to induce the differentiation of these cells. Type I IFNs have no direct effects on T-helper cell differentiation, but may regulate, especially in humans, the expression of the IL-12 receptor and thus influence T-helper 1 differentiation. On the other hand, type I IFNs can have inhibitory effects on the cytokine production by differentiated T-helper 1 cells. This suggests an important regulatory role for type I IFNs in adaptive immunity.

Functional characterization of human IL-10.

Rapid progress has been made over the past two years in the characterization of the biological activities of interleukin-10. Interleukin-10, produced by T cells, B cells, macrophages/monocytes and keratinocytes, alters profoundly the morphology, the expression of MHC class II antigens and the production of cytokines by monocytes which in turn can affect a variety of immunological responses including antigen specific proliferation and cytokine production of both soluble and allo-antigens by T cells, cytokine production by natural killer cells and immunoglobulin production by B cells. IL-10 also directly affects the function and growth of T cells, B cells and mast cells. These characteristics indicate that IL-10 has strong anti-inflammatory activities and may act as a general suppressor factor of immune reactions with consequences for transplantation, tolerance, cancer therapy and infectious diseases.

Role of CD80 (B7.1) and CD86 (B7.2) in the immune response to an intracellular pathogen.

The costimulatory ligands CD80 and CD86 play a crucial role in the initiation and maintenance of an immune response. We demonstrate that whereas infection of human monocytes with viable tachyzoites of Toxoplasma gondii resulted in rapid induction of expression of CD80 and up-regulation of expression of CD86, incubation with killed organisms failed to alter the levels of expression of these costimulatory ligands. The T. gondii-mediated changes in levels of expression of these molecules are critical to the T cell response to the parasite. Proliferation of resting T cells in response to parasite-infected cells was dependent on both CD80 and CD86. More importantly, early production of IFN-gamma in response to T. gondii by T cells from T. gondii-seronegative individuals occurred only after stimulation with monocytes that exhibited increased expression of CD80 and CD86 (monocytes infected with viable parasites) and was almost completely ablated by the combination of anti-CD80 plus anti-CD86 mAb. Moreover, proliferation and IFN-gamma production by CD4+ CD45RA+ T cells from unexposed individuals were dependent on both CD80 and CD86. These data indicate that pathogen-monocyte interaction influences the ensuing T cell response.

Flow cytometric analysis of immunoprecipitates: high-throughput analysis of protein phosphorylation and protein-protein interactions.

BACKGROUND: Activation-induced protein phosphorylation can be studied by Western blotting, but this method is time consuming and depends on the use of radioactive probes for quantitation. We present a novel assay for the assessment of protein phosphorylation based on latex particles and flow cytometry. METHODS: This method employs monoclonal antibodies coupled to latex particles to immobilize protein kinase substrates. Their phosphorylation status is assessed by reactivity with phosphoepitope-specific antibodies. The amount of immobilized protein on the particles was analyzed by direct or indirect immunofluorescence with antibodies to nonphosphorylated epitopes. RESULTS: The assay allowed measurement of phosphorylation of multiple protein kinase substrates in stimulated T cells, including the zeta chain of the T-cell receptor, ZAP-70, CD3, CD5, SHP-1, and ERK-2, using 1-3 microg of total cell protein per sample. The assay provided high resolution of kinetics of phosphorylation and dephosphorylation. Interactions of protein kinase substrates with associated signaling molecules were demonstrated. CONCLUSIONS: The novel assay allows high-throughput quantitative measurement of protein modifications during signal transduction.

IL-12 transiently induces IFN-gamma transcription and protein synthesis in human CD4+ allergen-specific Th2 T cell clones.

IL-12 is a cytokine produced by monocytes and Epstein-Barr virus-transformed B cells which initiates Th1 responses by inducing the development of CD4+, IFN-gamma producing Th1 T cells in mouse and human. We have previously reported that allergen-specific CD4+ Th2 T cell clones produce IFN-gamma, following activation by phorbol ester (TPA) and calcium ionophore, indicating that these cells still have the ability to produce IFN-gamma. This observation, together with the capacity of IL-12 to induce IFN-gamma, prompted us to examine the effects of rIL-12 on the cytokine production profiles of a panel of cloned allergen-specific Th2 cell lines, and compare these to the effects of rIL-12 on the cytokine production by Th0 and Th1 T cell clones. Activation with antigen or TPA/anti-CD3 mAb of Th2 T cell clones that had been preincubated with rIL-12 and rIL-2 for 5 days induced or enhanced the expression of IFN-gamma transcripts, as well as the production of IFN-gamma by these cells. Furthermore, in a different set of experiments, it was found that the presence of rIL-12 during a 12 h stimulation of Th2 T cell clones induced or enhanced the expression of IFN-gamma transcripts, as well as the production of IFN-gamma by these cells. rIL-12 also enhanced IFN-gamma production by Th0 and Th1 T cells, but, in contrast, rIL-12 had no effect on the production of IL-4, nor on the frequency of IL-4 producing cells, as judged by analysis of intracellularly produced cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-10 down-regulates MHC class II alphabeta peptide complexes at the plasma membrane of monocytes by affecting arrival and recycling.

Interleukin-10 (IL-10) inhibits antigen-specific T cell responses when human monocytes are used as antigen-presenting cells. This is correlated with a down-regulation of MHC class II molecules on the surface of the monocyte. Here we show that IL-10 does not affect MHC class II transcription, polypeptide synthesis, subunit assembly, or antigenic peptide loading. Instead, newly synthesized mature MHC class II molecules are localized to the MHC class II loading compartment but are prevented from reaching the plasma membrane. In addition, treatment of monocytes with IL-10 leads to an accumulation of internalized MHC class II complexes in intracellular vesicles. These results indicate that IL-10 affects antigen presentation by regulating MHC exocytosis and recycling.

Regulation of germ-line epsilon transcription and induction of epsilon switching in cloned EBV-transformed and malignant human B cell lines by cytokines and CD4+ T cells.

IL-4 induces germ-line epsilon transcript synthesis in normal human B cells, but a second signal provided by CD4+ T cells is required for subsequent production of productive epsilon mRNA and IgE synthesis. In the present study we demonstrate that IL-4 specifically induces germ-line epsilon transcripts in most EBV lymphoblastoid (LCL) and EBV+ and EBV- Burkitt's lymphoma (BL) cells without inducing IgE synthesis. However, cocultivation of cloned sIgM+, sIgE- EBV-LCL or BL cells with activated CD4+ T cell clones in the presence of IL-4 resulted in IgE production in 13 to 24% of the wells. Analysis of rearranged DNA in IgE-producing cloned BL cells indicated that epsilon switching occurred through a recombination deletion event. IgE production is a stable feature of the cloned switched EBV-LCL and BL cells because these cells continued to produce relatively high levels of IgE in the absence of IL-4 and CD4+ T cells. Induction of IgE synthesis was blocked by IFN-gamma, IFN-alpha, and transforming growth factor beta (TGF-beta), but only TGF-beta inhibited IL-4-induced germ-line epsilon mRNA expression. These results suggest that the inhibitory effects of TGF-beta are mediated via inhibition of germ-line epsilon expression, whereas IFN-alpha and IFN-gamma block other steps in the regulatory processes resulting in induction of IgE synthesis by established human B cell line cells. Our results indicate that the same set of signals that induce normal B cells to switch to IgE synthesis also induce high frequency epsilon switching in cloned established EBV transformed and malignant B cell lines including classical cell lines such as JY and BL-2.

IL-2 and a contact-mediated signal provided by TCR alpha beta + or TCR gamma delta + CD4+ T cells induce polyclonal Ig production by committed human B cells. Enhancement by IL-5, specific inhibition of IgA synthesis by IL-4.

To study the role of T cells in T-B cell interactions resulting in isotype production, autologous purified human splenic B and T cells were cocultured in the presence of IL-2 and Con A. Under these conditions high amounts of IgM, IgG, and IgA were secreted. B cell help was provided by autologous CD4+ T cells whereas autologous CD8+ T cells were ineffective. Moreover, CD8+ T cells suppressed Ig production when added to B cells cocultured with CD4+ T cells. Autologous CD4+ T cells could be replaced by allogeneic activated TCR gamma delta,CD4+ or TCR alpha beta,CD4+ T cell clones with nonrelevant specificities, indicating that the TCR is not involved in these T-B cell interactions. In contrast, resting CD4+ T cell clones, activated CD8+, or TCR gamma delta,CD4-,CD8- T cell clones failed to induce IL-2-dependent Ig synthesis. CD4+ T-B cell interaction required cell-cell contact. Separation of the CD4+ T and B cells by semiporous membranes or replacement of the CD4+ T cells by their culture supernatants did not result in Ig synthesis. However, intact activated TCR alpha beta or TCR gamma delta,CD4+ T cell clones could be replaced by plasma membrane preparations of these cells. Ig synthesis was blocked by mAb against class II MHC and CD4. These data indicate that in addition to CD4 and class II MHC Ag a membrane-associated determinant expressed on both TCR alpha beta or TCR gamma delta,CD4+ T cells after activation is required for productive T-B cell interactions resulting in Ig synthesis. Ig production was also blocked by mAb against IL-2 and the IL-2R molecules Tac and p75 but not by anti-IL-4 or anti-IL-5 mAb. The CD4+ T cell clones and IL-2 stimulated surface IgM-IgG+ and IgM-IgA+, but not IgM+IgG- or IgM+IgA- B cells to secrete IgG and IgA, respectively, indicating that they induced a selective expansion of IgG- and IgA-committed B cells rather than isotype switching in Ig noncommitted B cells. Induction of Ig production by CD4+ T cell clones and IL-2 was modulated by other cytokines. IL-5 and transforming growth factor-beta enhanced, or blocked, respectively, the production of all isotypes in a dose-dependent fashion. Interestingly, IL-4 specifically blocked IgA production in this culture system, indicating that IL-4 inhibits only antibody production by IgA-committed B cells.

Interleukin-10 and the interleukin-10 receptor.

Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.