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.

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.

Up-regulation of IL-10R1 expression is required to render human neutrophils fully responsive to IL-10.

We have recently shown that IL-10 fails to trigger Stat3 and Stat1 tyrosine phosphorylation in freshly isolated human neutrophils. In this study, we report that IL-10 can nonetheless induce Stat3 tyrosine phosphorylation and the binding of Stat1 and Stat3 to the IFN-gamma response region or the high-affinity synthetic derivative of the c-sis-inducible element in neutrophils that have been cultured for at least 3 h with LPS. Similarly, the ability of IL-10 to up-regulate suppressor of cytokine signaling (SOCS)-3 mRNA was dramatically enhanced in cultured neutrophils and, as a result, translated into the SOCS-3 protein. Since neutrophils' acquisition of responsiveness to IL-10 required de novo protein synthesis, we assessed whether expression of IL-10R1 or IL-10R2 was modulated in cultured neutrophils. We detected constitutive IL-10R1 mRNA and protein expression in circulating neutrophils, at levels which were much lower than those observed in autologous monocytes or lymphocytes. In contrast, IL-10R2 expression was comparable in both cell types. However, IL-10R1 (but not IL-10R2) mRNA and protein expression was substantially increased in neutrophils stimulated by LPS. The ability of IL-10 to activate Stat3 tyrosine phosphorylation and SOCS-3 synthesis and to regulate IL-1 receptor antagonist and macrophage-inflammatory protein 1beta release in LPS-treated neutrophils correlated with this increased IL-10R1 expression, and was abolished by neutralizing anti-IL-10R1 and anti-IL-10R2 Abs. Our results demonstrate that the capacity of neutrophils to respond to IL-10, as assessed by Stat3 tyrosine phosphorylation, SOCS-3 expression, and modulation of cytokine production, is very dependent on the level of expression of IL-10R1.

Characterization of chemokines and chemokine receptors in two murine models of inflammatory bowel disease: IL-10-/- mice and Rag-2-/- mice reconstituted with CD4+CD45RBhigh T cells.

We used quantitative PCR to investigate the expression of chemokines and chemokine receptors in two Th1-mediated murine models of inflammatory bowel disease (IBD). First, mRNA levels encoding the chemokines MIG, RANTES, lymphotactin, MIP-3alpha, TCA-3, TARC, MIP-3beta, LIX, MCP-1 and MIP-1beta and the receptors CCR4, CCR6 and CCR2 were significantly increased in chronically inflamed colons of IL-10-/- mice when compared with wildtype mice. Interestingly, reversal of colitis in IL-10-/- mice by anti-IL-12 mAb was accompanied by the inhibition in the expression of LIX, lymphotactin, MCP-1, MIG, MIP-3alpha, MIP-3beta, TCA-3, CCR2 and CCR4, whereas the increased mRNA levels of MIP-1beta, RANTES, TARC and CCR6 were unaffected. Second, to investigate which chemokines and receptors were up-regulated during the inductive phase of colitis, we employed the CD4+CD45RBhigh T cell transfer model. At 4 and 8 weeks after reconstitution of Rag-2-/- mice the mRNA levels of IP-10, MCP-1, MDC, MIG, TARC, RANTES, CCR4 and CCR5 were significantly increased prior to the appearance of macroscopic lesions. Other chemokines and chemokine receptors were clearly associated with the acute phase of the disease when lesions were evident. The sum of our studies with these two models identifies chemokines that are expressed at constant levels, irrespective of inflammatory responses, and those that are specifically associated with acute and/or chronic stages of Th1-driven colitis.

Selective development of a strong Th2 cytokine profile in high-risk children who develop atopy: risk factors and regulatory role of IFN-gamma, IL-4 and IL-10.

BACKGROUND: The immunological processes in early life and their relation to allergic sensitization leading to a Th2 cytokine profile are still not well understood. OBJECTIVE: To analyse the environmental and genetic risk factors and immunological responses at birth in relation to the development of atopic disease at 12 months of age in a longitudinal study of high-risk children. METHODS: High-risk children were followed from birth till 12 months of age. Mononuclear cells obtained at birth and 6 and 12 months thereafter were analysed for their proliferative and cytokine responses after polyclonal and allergen-specific stimulation. RESULTS: At 12 months of age 25% children had developed an atopic disease. Two atopic parents, parental smoking and atopic dermatitis of at least one of the parents were significant risk factors. In cord blood of newborns who developed atopy, an increased percentage of CD4+CD45RO+ cells and an increased polyclonal-stimulated proliferation were observed. Furthermore, an impaired allergen-induced, but not polyclonal-stimulated IFN-gamma production was found, suggesting a regulatory defect. At 6 and 12 months of age, a strong Th2 profile (characterized by increased levels of IL-4, IL-5, and IL-13) after both polyclonal and, to a lesser extent, allergen-specific stimulation was found in the children developing atopy. Allergen-induced IL-10 production at 12 months of age was only observed in the non-atopic children. CONCLUSION: Our data indicate that the first 6 months of life represent a critical time window for the initiation of immunological changes resulting in the development of atopy. The selective development of a Th2 cytokine profile in high-risk children who develop atopy is due to increased production of Th2 cytokines, possibly caused by impaired allergen-induced IFN-gamma production in the neonatal period. Furthermore, the decreased allergen-induced IL-10 levels observed in the atopic children at 12 months of age may result in a lack of down-regulation of the inflammatory process.

Human thymic stromal lymphopoietin preferentially stimulates myeloid cells.

The sequence of a novel hemopoietic cytokine was discovered in a computational screen of genomic databases, and its homology to mouse thymic stromal lymphopoietin (TSLP) suggests that it is the human orthologue. Human TSLP is proposed to signal through a heterodimeric receptor complex that consists of a new member of the hemopoietin family termed human TSLP receptor and the IL-7R alpha-chain. Cells transfected with both receptor subunits proliferated in response to purified, recombinant human TSLP, with induced phosphorylation of Stat3 and Stat5. Human TSLPR and IL-7Ralpha are principally coexpressed on monocytes and dendritic cell populations and to a much lesser extent on various lymphoid cells. In accord, we find that human TSLP functions mainly on myeloid cells; it induces the release of T cell-attracting chemokines from monocytes and, in particular, enhances the maturation of CD11c(+) dendritic cells, as evidenced by the strong induction of the costimulatory molecules CD40 and CD80 and the enhanced capacity to elicit proliferation of naive T cells.

IFN-alpha and IL-10 induce the differentiation of human type 1 T regulatory cells.

CD4(+) T regulatory type 1 (Tr1) cells suppress Ag-specific immune responses in vitro and in vivo. Although IL-10 is critical for the differentiation of Tr1 cells, the effects of other cytokines on differentiation of naive T cells into Tr1 cells have not been investigated. Here we demonstrate that endogenous or exogenous IL-10 in combination with IFN-alpha, but not TGF-beta, induces naive CD4(+) T cells derived from cord blood to differentiate into Tr1 cells: IL-10(+)IFN-gamma(+)IL-2(-/low)IL-4(-). Naive CD4(+) T cells derived from peripheral blood require both exogenous IL-10 and IFN-alpha for Tr1 cell differentiation. The proliferative responses of the Tr1-containing lymphocyte populations, following activation with anti-CD3 and anti-CD28 mAbs, were reduced. Similarly, cultures containing Tr1 cells displayed reduced responses to alloantigens via a mechanism that was partially mediated by IL-10 and TGF-beta. More importantly, Tr1-containing populations strongly suppressed responses of naive T cells to alloantigens. Collectively, these results show that IFN-alpha strongly enhances IL-10-induced differentiation of functional Tr1 cells, which represents a first major step in establishing specific culture conditions to generate T regulatory cells for biological and biochemical analysis, and for cellular therapy to induce peripheral tolerance in humans.

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.

Novel p19 protein engages IL-12p40 to form a cytokine, IL-23, with biological activities similar as well as distinct from IL-12.

A novel sequence discovered in a computational screen appears distantly related to the p35 subunit of IL-12. This factor, which we term p19, shows no biological activity by itself; instead, it combines with the p40 subunit of IL-12 to form a novel, biologically active, composite cytokine, which we term IL-23. Activated dendritic cells secrete detectable levels of this complex. IL-23 binds to IL-12R beta 1 but fails to engage IL-12R beta 2; nonetheless, IL-23 activates Stat4 in PHA blast T cells. IL-23 induces strong proliferation of mouse memory (CD4(+)CD45Rb(low)) T cells, a unique activity of IL-23 as IL-12 has no effect on this cell population. Similar to IL-12, human IL-23 stimulates IFN-gamma production and proliferation in PHA blast T cells, as well as in CD45RO (memory) T cells.

IL-18 receptors, their role in ligand binding and function: anti-IL-1RAcPL antibody, a potent antagonist of IL-18.

IL-18 is critical in eliciting IFN-gamma production from Th1 cells both in vitro and in vivo. Th1 cells have been implicated in the pathogenesis of autoimmune disorders, making antagonists of IL-18 promising therapeutics. However, specificity and binding characteristics of IL-18R components have only been superficially explored. In this study, we show that IL-1R related protein 1 (IL-1Rrp1) and IL-1R accessory protein-like (IL-1RAcPL) confer responsiveness to IL-18 in a highly specific (no response to other IL-1 ligands) and unique manner (no functional pairing with other IL-1Rs and IL-1R-like molecules). Cotransfection with both receptor components resulted in expression of both low and high affinity binding sites for IL-18 (K:(d) of 11 and 0.4 nM, respectively). We prepared anti-IL-1RAcPL mAb TC30-28E3, which, in contrast to soluble R proteins, effectively inhibited the IL-18-induced activation of NF-kappaB. Quantitative PCR showed that Th1 but not Th2 cells are unique in that they coexpress IL-1Rrp1 and IL-1RAcPL. mAb TC30-28E3 inhibited IL-18-induced production of IFN-gamma by Th1 cells, being at least 10-fold more potent than anti-IL-18 ligand mAb. This study shows that IL-1RAcPL is highly specific to IL-18, is required for high affinity binding of IL-18, and that the anti-IL-1RAcPL mAb TC30-28E3 potently antagonizes IL-18 responses in vitro, providing a rationale for the use of anti-IL-1RAcPL Abs to inhibit Th1-mediated inflammatory pathologies.

Cytokines and chemokines are both expressed by human myoblasts: possible relevance for the immune pathogenesis of muscle inflammation.

The idiopathic inflammatory myopathies are characterized by antibody- or cell-mediated immune response against unknown muscle tissue antigens. In these diseases a cellular infiltrate, composed of T and B lymphocytes, macrophages and NK cells, may invade muscle tissue with a gradient from the perivascular space to the endomysial compartment. Muscle cells may be actively involved in the processes of mononuclear cell recruitment and activation from the blood stream to the areas of inflammation. In order to verify this hypothesis, cultured human myoblasts were tested for their capacity to express different pro-inflammatory cytokines [IL-1alpha, IL-1beta, IL-6 and tumor necrosis factor (TNF)-alpha] and chemokines (IL-8, MCP-1 and RANTES) at the mRNA level and protein secretion, in the presence of the pro-inflammatory cytokines IFN-gamma and TNF-alpha alone or in combination. We confirmed that human myoblasts expressed IL-1alpha and IL-6 constitutively, while IL-1beta and TNF-alpha are detected only after treatment with pro-inflammatory cytokines; moreover, we observed that TNF-alpha was expressed on an autocrine fashion by myoblasts. IL-8 and RANTES were expressed constitutively while MCP-1 after proper induction. These molecular data were further confirmed by specific ELISA in the supernatant from cultured myoblasts. Our results underline the importance of human myoblasts in the recruitment of leukocytes from the blood stream and, most probably, in the cross-talk between infiltrating inflammatory cells and muscle cells, creating the conditions for a chronic inflammation. Moreover, the capacity of muscle cells to behave as cells of the immune system has to be kept in mind, also in view of i.m. vaccination and use of molecular engineered myoblasts as vehicles in gene therapy.

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.

Co-stimulation of T cells results in distinct IL-10 and TNF-alpha cytokine profiles dependent on binding to ICAM-1, ICAM-2 or ICAM-3.

The LFA-1 adhesion molecule is involved in cell adhesion events of leukocytes through binding to ICAM-1, ICAM-2 and ICAM-3. Whether binding to either of these ligands similarly affects co-stimulation of T cells and cytokine secretion is unknown. We demonstrated that LFA-1 co-stimulation under suboptimal concentrations of anti-CD3 monoclonal antibodies resulted in high, intermediate and weak proliferation of T cells on ICAM-1, -2, and -3, respectively, which correlates with the distinct affinities of LFA-1 for these ligands. Furthermore, we investigated whether binding to ICAM-1, -2 or -3 induced different cytokine profiles, thus regulating T helper cell function. Granulocyte-macrophage colony-stimulating factor and IFN-gamma were secreted in high amounts, whereas IL-2, IL-4 and IL-5 could not be detected. Interestingly, we observed that LFA-1/ICAM-1 co-stimulation of T cells resulted in high production of the Th2 cytokine IL-10 compared to ICAM-2 or ICAM-3 co-stimulation. In contrast, ICAM-2 and ICAM-3 induced a much stronger secretion of the Th1 cytokine TNF-alpha compared to LFA-1/ICAM-1 induced co-stimulation, despite the lower proliferation rate. These results demonstrate that besides facilitating cell adhesion, LFA-1 serves as a potent co-stimulatory molecule by inducing different cytokine patterns depending on the ligand bound.

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.

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.

Diversity of the anti-T-cell receptor immune response and its implications for T-cell vaccination therapy of multiple sclerosis.

More precise understanding of the immune response against T-cell receptors (TCRs) is a prerequisite for successful TCR vaccination therapy of multiple sclerosis and other neurological autoimmune diseases. We conducted a detailed analysis of a paradigmatic anti-TCR response, using synthetic TCR peptides and highly purified recombinant TCR V alpha and Vbeta variable chains for the selection of CD4+ T-cell lines from a healthy volunteer. The target TCR (designated TCR(HWBP-3)) was obtained from HWBP-3, an autologous CD4+ T-cell line specific for myelin basic protein. The V alpha and Vbeta chains of TCR(HWBP-3) were expressed in Escherichia coli and purified by Ni-chelate chromatography and SDS (sodium dodecyl sulphate) gel electrophoresis. Further, we synthesized a set of 13- to 22-mer peptides spanning the complementarity-determining regions (CDR) 1, 2 and 3 and the framework regions (FR) of the alpha and beta chains of TCR(HWBP-3). The TCR peptides and proteins were then used to select a panel of TCR-specific CD4+ T-cell lines from donor HW. Several T-cell lines cross-reacted with a recombinant V chain and synthetic peptide. Cross-reactive immunogenic TCR epitopes were identified in the FR1 and CDR3 regions of the TCR(HWBP-3) alpha chain and in the FR1, CDR1 and CDR2 regions of the TCR(HWBP-3) beta chain. The TCR proteins and peptides were recognized in the context of at least three different HLA-DR molecules [DR2a (DRB5*0101), DR2b (DRB1*1501) and DRB1*1401/DRB3*0202]. Notably, the majority of the TCR peptide-selected T-cell lines did not react with the full-length recombinant V chains, suggesting they recognize 'cryptic' determinants. Based on the diversity of the anti-TCR immune response, we suggest that candidate TCR peptides should be screened in vitro in functional experiments before they are clinically applied for TCR vaccination therapy.

Alpha beta T cell response to Toxoplasma gondii in previously unexposed individuals.

The mechanisms by which T cells from previously unexposed hosts respond in vitro to certain intracellular pathogens remain to be fully understood. We report and characterize the in vitro reactivity to Toxoplasma gondii of human alpha beta T cells from T. gondii-seronegative individuals. Resting alpha beta T cells from these individuals proliferated in response to PBMC infected with T. gondii or pulsed with T. gondii lysate Ags. This was accompanied by an increase in the percentage of CD4+ alpha beta T cells. Purified CD4+ alpha beta T cells but not CD8+ alpha beta T cells proliferated in response to these T. gondii preparations. Both CD4+ alpha beta T cells with naive (CD45RA+) and memory (CD45RO+) phenotypes from adults as well as alpha beta T cells from T. gondii-seronegative newborns proliferated after incubation with T. gondii. This alpha beta T cell response to the parasite was inhibited by anti-HLA-DR mAb and to a lesser degree by anti-HLA-DQ mAb. Use of paraformaldehyde-fixed PBMC completely abrogated the proliferation of alpha beta T cells, indicating the need for processing of T. gondii Ags. Analysis of the TCR V beta expression did not show evidence for restriction in TCR V beta usage during T. gondii stimulation of alpha beta T cells. Alpha beta T cells secreted significant amounts of IFN-gamma after incubation with T. gondii-infected monocytes. This rapid and remarkable alpha beta T cell response may play an important role in the early events of the immune response to T. gondii.

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.

Multiple sclerosis: comparison of the human T-cell response to S100 beta and myelin basic protein reveals parallels to rat experimental autoimmune panencephalitis.

The adoptive transfer of autoreactive S100 beta-specific T cells induces experimental autoimmune panencephalomyelitis and uveoretinitis in the Lewis rat, mimicking the distribution of lesions seen in a subset of patients with multiple sclerosis. We studied the frequency and functional properties of the human T-cell response to S100 beta in eight patients (two relapsing-remitting multiple sclerosis, one chronic-progressive multiple sclerosis, two with multiple sclerosis and uveitis, two neuromyelitis optica, one panuveitis) and in seven healthy individuals, using bovine S100 beta for T-cell stimulation. Both in patients and controls, the frequency of S100 beta-specific T-cell responses was half of that obtained for myelin basic protein (MBP), and only 10% of that obtained using purified protein derivative (PPD). The stimulation indices obtained in response to S100 beta were also less than half those obtained with either MBP or PPD. However, four long-term S100 beta-specific T-cell lines were established and studied in more detail. The four T-cell lines all exhibited a CD4+, CD8-, T-cell receptor alpha beta + surface phenotype and secreted tumour necrosis factor-alpha, interferon-gamma, interleukin-10 and interleukin-4 upon antigenic stimulation, but they were heterogenous with respect to T-cell receptor usage; two T-cell lines expressed V beta 2, one V beta 6.7 and one V beta 13. Antigen-specificity was confirmed using bovine S100 beta beta and alpha beta-isoforms, as well as a recombinant rat S100 beta preparation. The response to S100 beta was shown to the HLA-(human leukocyte antigen-) DR-restricted for two of the S100 beta-specific T-cell lines. Human S100 beta-specific T-cell lines were cytotoxic, although to a lesser extent than MBP-specific T-cell lines derived from the same donors. The phenotypic and functional properties of human S100 beta-specific T-cell lines raise the possibility that these T cells are pathogenic, as they are in the rat. The low frequency and proliferative index of S100 beta-specific, as opposed to MBP-specific T-cell responses suggests that the T-cell response to this widely expressed calcium-binding protein is under more efficient regulatory control.

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.