Production of granulocyte-macrophage colony-stimulating factor by T cells is regulated by B7 and IL-1 beta

Increased frequency of GM-CSF secreting PBMC in patients with active systemic lupus erythematosus can be reduced by immunoadsorption

An objective was to determine the frequency of GM-CSF secreting peripheral blood mononuclear cells (PBMC) in patients with active systemic lupus erythematosus (SLE) and their relation to other cytokine secreting PBMC, activation markers on lymphocytes/monocytes, clinical manifestations and anti- dsDNA antibodies.A second objectivewas to further investigatethe influence of immunoadsorption(IA) therapy on these parameters.The number of GM-CSF, interleukin-1b (IL-1b), IL-6, interferon-g (INF-g) or tumour necrosis factor-a (TNF-a) secreting PBMC was assessed by ELISPOT assay in 10 patients with active SLE. Further, the expression of activation markers on lymphocytes and monocytes was determined by flow cytometry. Three courses of IA were performed in the patients. Seventeen healthy, age- and sex-matched volunteers served as controls. GM-CSF secreting PBMC were significantly increased whereas INF-g secreting cells were decreased in SLE patients. The expression of CD71 (transferrin receptor) on CD4 + T-cells and of the costimulatorymolecule CD86 on B-lymphocyteswas significantly increased in SLE patients. GM-CSF secreting PBMC and CD4 + /CD71 + T-cells correlated with anti-dsDNA antibody titres and decreased towards levels of controls during IA. Disease activity and anti-dsDNA autoantibody titres were significantly reduced after the treatment. Our results demonstrate significant alterations of cellular and humoral immunity in SLE patients. The impaired immunity can be modulated by IA. Thus IA may prove an immunomodulatory therapeutic option in addition to the mere depletion of anti-dsDNA autoantibodies.

The role of granulocyte macrophage-colony-stimulating factor in acute intestinal inflammation

An imbalance of mucosal pro- and anti-inflammatory cytokines is crucial in the pathogenesis of inflammatory bowel disease (IBD). GM-CSF influences the development of hemopoietic cells. The precise role of GM-CSF in IBD remains to be elucidated. GM-CSF gene knockout (GM-CSF(-/-)) and wild-type (Wt) mice were challenged with 2.5% dextran sulfate sodium (DSS) for 7 days. The ensued clinical and pathological changes, macrophage infiltration, colonic cytokine production, and bacterial counts were examined. DSS-treated GM-CSF(-/-) mice developed more severe acute colitis than DSS-treated Wt mice, reflected by a greater body weight loss, more rectal bleeding, and aggravated histopathological changes. More infiltrating macrophages were observed in GM-CSF(-/-), compared with Wt mice following DSS challenge, correlating with monocyte chemoattractant protein-1 (MCP-1) production. The levels of colonic IL-17 and TNF-alpha were increased significantly in GM-CSF(-/-) mice, but not in Wt mice, following DSS administration. The level of IL-6 was increased by 1.5- and 2-fold in the colon of GM-CSF(-/-) and Wt mice, respectively, following DSS challenge. No significant changes in IL-4 and IFN-gamma were detected in Wt and GM-CSF(-/-) mice following DSS treatment. The bacteria recovery from colon was increased about 15- and 5-fold, respectively, in Wt mice and GM-CSF(-/-) mice following DSS challenge. These results suggest that GM-CSF(-/-) mice are more susceptible to acute DSS-induced colitis, possibly because of an impaired gut innate immune response as a result of diminished GM-CSF.

Induction of T-Cell Apoptosis in Rats by Genetically Engineered Glioma Cells Expressing Granulocyte-Macrophage Colony-Stimulating Factor and B7.1

PURPOSE

To evaluate antitumor effects on intracerebral gliomas of genetically engineered tumor vaccines expressing granulocyte-macrophage colony-timulating factor (GM-CSF), B7.1, or both (combination).

EXPERIMENTAL DESIGN

A rat glioma cell line, RT-2, was engineered with a retroviral vector to express GM-CSF, B7.1, or combination. Tumorigenicity of engineered cells and therapeutic effects of s.c. given irradiated or live tumor vaccines on parental intracerebral gliomas were studied. Immune cell infiltration induced at vaccine and tumor sites was examined by histologic and immunohistochemical staining. Apoptosis of T cells from vaccine sites was analyzed with fluorescence-activated cell sorting.

RESULTS

Engineered RT-2 cells exhibited reduced s.c. tumorigenicity in rats with reduced tumor growth and prolonged animal survival time compared with control rats. Rats with intracerebral gliomas s.c. treated with irradiated or live GM-CSF-expressing vaccines had 60% and 100% survival rates, respectively, significantly better than the control groups (P < 0.05). In contrast, rats treated with vaccines expressing B7.1 or the combination had no or mild therapeutic effects. Studies revealed less T-cell infiltration at both vaccine and tumor sites in rats treated with vaccines expressing B7.1 or the combination than in rats treated with a vaccine expressing GM-CSF. Cell sorting analyses revealed higher proportions of apoptotic T cells at vaccine sites of rats treated with the combination than those treated with vaccine expressing GM-CSF.

CONCLUSIONS

Combination of GM-CSF- and B7.1-expressing tumor vaccines exerted no synergistic, or even worse, therapeutic effects on gliomas compared with single GM-CSF-secreting tumor vaccine. The worse therapeutic effects of the GM-B7.1-expressing tumor vaccine than the GM-CSF-expressing tumor vaccine were related to the reduced T-cell amount and increased T-cell apoptosis in the former.

Expression of the dendritic cell-associated C-type lectin DC-SIGN by inflammatory matrix metalloproteinase-producing macrophages in rheumatoid arthritis synovium and interaction with intercellular adhesion molecule 3-positive T cells

OBJECTIVE

To determine whether matrix metalloproteinase (MMP)-producing inflammatory macrophages in the synovium of rheumatoid arthritis (RA) patients express the novel dendritic cell (DC)-specific C-type lectin DC-SIGN and whether this expression is associated with the presence of naive T cells expressing the DC-SIGN ligand, intercellular adhesion molecule 3 (ICAM-3).

METHODS

Reverse transcription-polymerase chain reaction was performed to study the expression of DC-SIGN in synovium samples from RA, osteoarthritis (OA), and trauma patients. DC-SIGN expression on RA monocytes or on monocytes stimulated with granulocyte-macrophage colony-stimulating factor and interleukin-4 was further investigated by flow cytometry. To localize DC-SIGN in the synovium, the DC markers ICAM-3 and MMP-1 were analyzed by immunohistochemistry (single and double labeling) on serial cryostat sections.

RESULTS

Seventy percent of the inflammatory cells in the synovium of RA patients showed high expression of DC-SIGN. DC-SIGN was expressed by 80% of CD68-positive macrophages, but not by CD83-positive, DC-LAMP-positive, or Fascin-positive cells. Normal numbers of DC-SIGN-positive cells were found in the peripheral blood of RA patients, suggesting that DC-SIGN is up-regulated locally in the joint. In RA synovium, ICAM-3-positive resting T cells were found in close proximity to DC-SIGN cells. Unexpectedly, a lower percentage of DC-SIGN-expressing cells was found in OA synovium compared with RA synovium. Furthermore, ICAM-3-expressing T cells, which are known to bind DC-SIGN, were almost absent within the synovium of OA and trauma patients. DC-SIGN-positive macrophages adjacent to these T cells were located in close proximity to the cartilage-degrading proteins extracellular MMP inducer (EMMPRIN) and MMP-1.

CONCLUSION

The C-type lectin DC-SIGN is almost absent in the synovium of trauma patients but is highly expressed by most CD68-positive macrophages in the synovium of RA patients. The lack of correlation between DC-SIGN expression and the expression of CD83, DC-LAMP, or Fascin indicates that multiple DC/macrophage subsets are present in RA synovium. Expression of DC-SIGN and its ligand, ICAM-3, is found in substantial amounts only in RA synovium, suggesting that their interaction is implicated in the additional activation of synovial macrophages that leads to the production of EMMPRIN and MMP-1.

Superantigen-induced CD4 T cell tolerance mediated by myeloid cells and IFN-gamma

We have previously shown that systemic staphylococcal enterotoxin A (SEA) injections cause CD4 T cells in TCR-transgenic mice to become tolerant to subsequent ex vivo restimulation. An active IFN-gamma-dependent mechanism of suppression was responsible for the apparent unresponsiveness of the CD4 T cells. In this study, we analyze the response of CD4 T cells isolated throughout the first 10 days of the in vivo response to injected SEA. We show that CD4 T cells isolated at the peak of the in vivo response undergo very little activation-induced cell death after sterile FACS sorting or restimulation in the presence of neutralizing Abs to IFN-gamma. We also show that the IFN-gamma-dependent tolerance develops soon after SEA injection in the spleens of both normal and TCR-transgenic mice. This suppression is dependent upon myeloid cells from the SEA-treated mice and is optimal when inducible NO synthase activity and reactive oxygen intermediates are both present. The data indicate that IFN-gamma, myeloid cells, and a combination of NO and reactive oxygen intermediates all contribute to a common pathway of T cell death that targets activated or responding CD4 T cells. Sorted Gr-1(+) cells from SEA-treated mice also directly suppress the response of naive CD4 T cells in mixed cultures, indicating that this tolerance mechanism may play a role in down-regulating other vigorous immune responses.

Granulocyte-Macrophage Colony-Stimulating Factor Upregulates Reduced 5-Lipoxygenase Metabolism in Peripheral Blood Monocytes and Neutrophils in Acquired Immunodeficiency Syndrome

Leukotrienes (LT) are mediators derived from the 5-lipoxygenase (5-LO) pathway, which play a role in host defense, and are synthesized by both monocytes (peripheral blood monocyte [PBM]) and neutrophils (PMN). Because 5-LO metabolism is reduced in alveolar macrophages and PMN from acquired immunodeficiency syndrome (AIDS) subjects, we investigated the synthesis of LT by PBM and PMN from these subjects. There was a reduction (74.2% ± 8.8% of control) in LT synthesis in PBM from human immunodeficiency virus (HIV)-infected compared with normal subjects. Expression of 5-LO (51.2% ± 8.8% of control), and 5-LO activating protein (FLAP) (48.5% ± 8.0% of control) was reduced in parallel. We hypothesized that this reduction in LT synthetic capacity in PBM and PMN was due to reduced cytokine production by CD4 T cells, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). We treated 10 AIDS subjects with GM-CSF for 5 days. PBM 5-LO metabolism ex vivo was selectively increased after GM-CSF therapy and was associated with increased 5-LO and FLAP expression. PMN leukotriene B4(LTB4) synthesis was also augmented and associated with increased 5-LO, FLAP, and cytosolic phospholipase A2 expression. In conclusion, as previously demonstrated for PMN, PBM from AIDS subjects also demonstrate reduced 5-LO metabolism. GM-CSF therapy reversed this defect in both PBM and PMN. In view of the role of LT in antimicrobial function, cytokine administration in AIDS may play a role as adjunct therapy for infections.

Granulocyte-Macrophage Colony-Stimulating Factor Upregulates Reduced 5-Lipoxygenase Metabolism in Peripheral Blood Monocytes and Neutrophils in Acquired Immunodeficiency Syndrome

Leukotrienes (LT) are mediators derived from the 5-lipoxygenase (5-LO) pathway, which play a role in host defense, and are synthesized by both monocytes (peripheral blood monocyte [PBM]) and neutrophils (PMN). Because 5-LO metabolism is reduced in alveolar macrophages and PMN from acquired immunodeficiency syndrome (AIDS) subjects, we investigated the synthesis of LT by PBM and PMN from these subjects. There was a reduction (74.2% ± 8.8% of control) in LT synthesis in PBM from human immunodeficiency virus (HIV)-infected compared with normal subjects. Expression of 5-LO (51.2% ± 8.8% of control), and 5-LO activating protein (FLAP) (48.5% ± 8.0% of control) was reduced in parallel. We hypothesized that this reduction in LT synthetic capacity in PBM and PMN was due to reduced cytokine production by CD4 T cells, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). We treated 10 AIDS subjects with GM-CSF for 5 days. PBM 5-LO metabolism ex vivo was selectively increased after GM-CSF therapy and was associated with increased 5-LO and FLAP expression. PMN leukotriene B4(LTB4) synthesis was also augmented and associated with increased 5-LO, FLAP, and cytosolic phospholipase A2 expression. In conclusion, as previously demonstrated for PMN, PBM from AIDS subjects also demonstrate reduced 5-LO metabolism. GM-CSF therapy reversed this defect in both PBM and PMN. In view of the role of LT in antimicrobial function, cytokine administration in AIDS may play a role as adjunct therapy for infections.

Combination of CD80 and granulocyte-macrophage colony-stimulating factor coexpression by a leukemia cell vaccine: preclinical studies in a murine model recapitulating Philadelphia chromosome-positive acute lymphoblastic leukemia

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is a highly aggressive malignancy caused by the bcr-abl translocation oncogene. To explore alternative treatments for Ph+ ALL we tested gene-modified cell vaccines in the BALB/c-derived BM185 leukemia model. We compared the efficacy of BM185 cell vaccine expressing CD80 alone or in combination with IL-2 or GM-CSF. Mice injected with viable BM185 leukemia cells modified to express CD80 and GM-CSF (BM185/CD80+GM-CSF) showed the highest leukemia rejection rates. Cell vaccines consisting of irradiated BM185/CD80+GM-CSF cells administered subcutaneously stimulated a potent cytotoxic T lymphocyte (CTL) response against parental BM185. Histological examination of the vaccination site showed a large concentration of immune cells. Administration of the BM185/CD80+GM-CSF cell vaccine before intravenous challenge with parental cells caused strong inhibition of leukemia development. Vaccination after subcutaneous challenge with BM185 cells caused efficient elimination of leukemia promoting 40-60% long-term survival rates. The immunization efficacy of the BM185/CD80+ GM-CSF cell vaccine was directly correlated with the percentage of cells expressing the transgenes. In all, this preclinical study shows that leukemia cell vaccines coexpressing CD80 and GM-CSF can potentially be explored for immunotherapy in Ph+ ALL patients.

An inhibitor of CD28-CD80 interactions impairs CD28-mediated costimulation of human CD4 T cells

We have identified and characterized a microbial extract-derived inhibitor of T cell CD28-dependent costimulation, NP1835-2, utilizing an in vitro system in which anti-human CD3 antibody and a human CD80-Ig fusion protein are immobilized on protein A-coated microspheres. This system is CD28-CD80-dependent, as judged by the specific ability of anti-CD80 antibody or cytotoxic T lymphocyte antigen-4-Ig to block human CD4 T cell responses. Activation of CD4 T cells in this system in presence of NP1835-2 resulted in a concentration-dependent inhibition of T cell proliferation (IC50 of 1-4 microg/ml), surface activation marker expression, and the production of many T cell cytokines, with the exception of TGFbeta. Impairment of T cell activation correlated with a blockade of cell cycle progression at G0/G1 and was only partly restored by addition of 100 U/ml IL-2. No inhibition by NP1835-2 of T cell proliferation stimulated by plate-bound anti-CD3 antibody, phorbol 12-myristate 13-acetate + A23187, or P815 cells expressing the costimulatory molecule CD58 was observed. NP1835-2 was unable to modulate anti-IgM-stimulated B cell proliferation or LPS-induced monocyte activation. Suboptimal concentrations of NP1835-2 and cyclosporin together were able to impair T cell activation in an additive fashion. NP1835-2 was also able to inhibit the primary human MLR. These data indicate that NP1835-2 may belong to a class of molecules capable of selectively impairing CD28-mediated T cell costimulation and suggest its potential usefulness in the treatment of a variety of T cell-dependent diseases. Moreover, NP1835-2 may serve as a useful probe for investigating the mechanisms involved in T cell nonresponsiveness.

CD80, CD86 and CD40 provide accessory signals in a multiple-step T-cell activation model

In this review, a sequential multiple-step model for T-cell activation is proposed. In a series of in vitro studies, highly purified freshly isolated human peripheral blood T lymphocytes were stimulated through the CD28 receptor, with mAb or with natural ligands B7-1 or B7-2, along with TCR stimulation, in the absence of other costimulatory interactions. Ligation of the CD28 receptor, along with stimulation of the TCR, was found to up-regulate pleiotropic in vitro activities, including the secretion of both Th1 and Th2-type cytokines, B-cell help, and the development of cytotoxic activity. This costimulatory action involves CD4+ and CD8+ as well as naive and memory T-cell subsets. The expression of B7-1 and B7-2 on professional APC in situ in both normal and pathological tissues, and its up-regulation on monocytes by GM-CSF and IFN-gamma is consistent with this role. Additional studies have addressed the contribution of interactions between CD28 and B7-1 and B7-2 in T-cell activation initiated by normal un-engineered APC, such as stimulation with recall antigens and primary MLR. Blockade of the interaction between CD28 and B7-1/B7-2 under these conditions failed to completely inhibit T-cell responses or to induce anergy. Complete inhibition and anergy were, however, induced with a combination of CsA, targeting downstream TCR-triggered signalling, as well as anti-B7-1- and anti-B7-2-directed reagents. Interestingly, and in contrast to anti-LFA-1 mAb, the addition of anti-B7-1 or anti-B7-2 reagents could be delayed until at least 48 h after the initiation of T-cell stimulation, indicating a requirement for a late interaction between CD28 and its counter-receptors. Interactions between CD40L on activated T cells and CD40 on APC may serve to sustain, enhance or prolong the presentation of B7-1 or B7-2 on the APC, and thus to prevent anergy induction, or ineffective or abortive T-cell stimulation. Based on these data a sequential multiple-step T-cell activation model is proposed, and novel strategies for immuno-intervention can be designed.