Induction of interleukin 1 alpha (IL-1 alpha) and IL-1 beta mRNA expression and cellular IL-1 production by anti-HLA-DR antibodies in human monocytes

Activation of MyD88 signaling upon staphylococcal enterotoxin binding to MHC class II molecules

Ligands binding to Toll-like receptor (TLR), interleukin 1 receptor (IL-1R), or IFN-γR1 are known to trigger MyD88-mediated signaling, which activates pro-inflammatory cytokine responses. Recently we reported that staphylococcal enterotoxins (SEA or SEB), which bind to MHC class II molecules on APCs and cross link T cell receptors, activate MyD88- mediated pro-inflammatory cytokine responses. We also reported that MyD88^−/− mice were resistant to SE- induced toxic shock and had reduced levels of serum cytokines. In this study, we investigated whether MHC class II- SE interaction by itself is sufficient to activate MyD88 in MHC class II⁺ cells and induce downstream pro-inflammatory signaling and production of cytokines such as TNF-α and IL-1β. Here we report that human monocytes treated with SEA, SEB, or anti-MHC class II monoclonal antibodies up regulated MyD88 expression, induced activation of NF-kB, and increased expression of IL-1R1 accessory protein, TNF-α and IL-1β. MyD88 immunoprecipitated from cell extracts after SEB stimulation showed a greater proportion of MyD88 phosphorylation compared to unstimulated cells indicating that MyD88 was a component of intracellular signaling. MyD88 downstream proteins such as IRAK4 and TRAF6 were also up regulated in monocytes after SEB stimulation. In addition to monocytes, primary B cells up regulated MyD88 in response to SEA or SEB stimulation. Importantly, in contrast to primary B cells, MHC class II deficient T2 cells had no change of MyD88 after SEA or SEB stimulation, whereas MHC class II-independent activation of MyD88 was elicited by CpG or LPS. Collectively, these results demonstrate that MHC class II utilizes a MyD88-mediated signaling mechanism when in contact with ligands such as SEs to induce pro-inflammatory cytokines.

Glatiramer acetate triggers PI3Kδ/Akt and MEK/ERK pathways to induce IL-1 receptor antagonist in human monocytes

Glatiramer acetate (GA), an immunomodulator used in multiple sclerosis (MS) therapy, induces the production of secreted IL-1 receptor antagonist (sIL-1Ra), a natural inhibitor of IL-1β, in human monocytes, and in turn enhances sIL-1Ra circulating levels in MS patients. GA is a mixture of peptides with random Glu, Lys, Ala, and Tyr sequences of high polarity and hydrophilic nature that is unlikely to cross the blood-brain barrier. In contrast, sIL-1Ra crosses the blood-brain barrier and, in turn, may mediate GA anti-inflammatory activities within the CNS by counteracting IL-1β activities. Here we identify intracellular signaling pathways induced by GA that control sIL-1Ra expression in human monocytes. By using kinase knockdown and specific inhibitors, we demonstrate that GA induces sIL-1Ra production via the activation of PI3Kδ, Akt, MEK1/2, and ERK1/2, demonstrating that both PI3Kδ/Akt and MEK/ERK pathways rule sIL-1Ra expression in human monocytes. The pathways act in parallel upstream glycogen synthase kinase-3α/β (GSK3α/β), the knockdown of which enhances sIL-1Ra production. Together, our findings demonstrate the existence of signal transduction triggered by GA, further highlighting the mechanisms of action of this drug in MS.

MyD88-dependent pro-inflammatory cytokine response contributes to lethal toxicity of staphylococcal enterotoxin B in mice

An elevated pro-inflammatory cytokine response is the primary cause of death by toxic shock after exposure to staphylococcal enterotoxin B (SEB). Identifying an intracellular signal mediator that predominantly controls the pro-inflammatory response is important for developing a therapeutic strategy. We examined the role of the signaling adaptor MyD88 in cell culture and in a mouse model of toxic shock. Our results indicated that elevated tumor necrosis factor-α, interferon-γ, interleukin (IL)-1α/β and IL-6 production from mouse spleen cells treated with SEB alone or in combination with lipopolysaccharide (LPS) was regulated by MyD88. Elevated levels of MyD88 protein in spleen cells, as well as in CD11c+ or Mac3+ cells, and activation of nuclear factor-κB in spleen cells were observed in mice treated with SEB. An SEB-dose dependent lethality was observed in LPS-potentiated and in D-galactosamine-sensitized mice. D-Galactosamine treatment of spleen cells had no effect in cytokine induction but rather increased the sensitivity to toxic shock in mice. Our results demonstrated an impaired pro-inflammatory cytokine production by spleen cells of MyD88–/– mice in response to SEB or SEB plus LPS. Most importantly, MyD88–/– mice were resistant to SEB-induced death. These results demonstrate that MyD88-dependent pro-inflammatory signaling is responsible for SEB intoxication. In addition, our studies also demonstrated that LPS potentiation, in comparison to D-galactosamine sensitization, contributes to a stronger SEB–induced lethality. This is due to the pro-inflammatory cytokine response elicited by MyD88 after exposure to SEB and LPS. These findings offer an important insight upon SEB intoxication and subsequent therapy targeting MyD88.

Staphylococcal enterotoxin A induction of pro-inflammatory cytokines and lethality in mice is primarily dependent on MyD88

Staphylococcal enterotoxin (SE) -induced toxic shock is triggered by inflammatory cytokine signal amplification after SE binding to major histocompatibility complex class II molecules on antigen-presenting cells and T-cell receptors. Identifying host cellular elements contributing to this pro-inflammatory signal amplification is critical for developing a strategy for therapeutic intervention. Myeloid differentiation primary-response protein 88 (MyD88) is an intracellular signalling adaptor protein primarily known for mediating pro-inflammatory cytokine responses. We investigated the role of MyD88 in staphylococcal enterotoxin A (SEA) -treated cell cultures and mouse models of toxic shock. Our results demonstrated that elevated levels of tumour necrosis factor-alpha, interferon-gamma, interleukin-1alpha/beta (IL-1alpha/beta), IL-2 and IL-6 production correlated with up-regulation of MyD88 after treatment of spleen cells and mice with SEA alone or in combination with lipopolysaccharide (LPS). The SEA-induced lethality was also observed in (LPS-independent) D-galactosamine-sensitized mice. While LPS potentiated SEA-induced cytokine responses, D-galactosamine treatment had no additive effect. Most importantly, our results demonstrated that MyD88(-/-) mice were resistant to SEA-induced toxic shock and had reduced pro-inflammatory cytokine responses. These results suggest that SEA-induced lethality is primarily dependent on MyD88. Our findings offer an important insight on potential therapeutic treatment of SEA-induced toxic shock targeting MyD88.

Generation of inflammatory cytokines and chemokines from peripheral blood mononuclear cells by HLA Class II antibody-containing plasma unit that was associated with severe nonhemolytic transfusion reactions

BACKGROUND

HLA Class II antibodies are thought to be involved in severe transfusion reactions including transfusion-related acute lung injury (TRALI). The activation of monocytes by HLA Class II antibody may play an important role in the etiology of TRALI.

CASE REPORT

An 81-year-old man with non-Hodgkin's lymphoma (Clinical Stage IIIA) received a plateletpheresis unit containing at least 4 x 10(11) platelets because of thrombocytopenia and a bleeding tendency. Approximately 30 minutes after the start of transfusion, he developed chills, tachycardia, dyspnea, lumber, and abdominal pain and then a fever (40.3 degrees C). His SaO(2) dropped to 70 percent. The transfusion was discontinued immediately. His symptoms disappeared after treatment with oxygen and the administration of corticosteroid and aminophyrine. A chest X-ray showed no sign of pulmonary edema.

RESULTS

The donor serum sample had HLA-DR antibodies against multiple DR antigens including DR13, the recipient's HLA-DR type. The cross-match between the patient's lymphocytes and the donor serum was positive. The treatment of peripheral blood mononuclear cells from healthy subjects bearing DR13 antigen with the donor plasma caused the secretion of inflammatory cytokines (i.e., interleukin [IL]-1beta, IL-6, and tumor necrosis factor-alpha) and neutrophil-activating chemokines (i.e., IL-8 and CXCL1/GRO-alpha) in a cognate antigen-antibody relationship. In addition, the secretion of inflammatory cytokines appeared to require the involvement of CD32 and/or CD16.

CONCLUSION

HLA-DR antibodies, detected in this case, had biologic functions to induce production of not only inflammatory cytokines but also neutrophil-attractant chemokines in vitro, which could contribute to the etiology of severe nonhemolytic transfusion reactions.

Susceptibility of lung transplants to preformed donor-specific HLA antibodies as detected by flow cytometry

BACKGROUND

Preformed anti-HLA antibodies are known to have the potential to induce early graft damage in organ transplant recipients. However, in lung transplant recipients, little information exists about the significance of preformed antibodies directed to either class I or class II HLA antigens.

METHODS

A two-color flow cytometry cross-match was performed in 92 consecutive lung transplant recipients using serum obtained immediately before transplantation. The presence of preformed antibodies was correlated with the incidence of severe graft dysfunction manifested as pulmonary infiltrates and severe hypoxemia with onset in the first few hours after transplantation.

RESULTS

Six patients (6.5%) had low-level anti-donor IgG antibodies detected by flow cytometry, four against T and two against B lymphocytes. Three patients (50%) developed severe graft dysfunction with pulmonary infiltrates and hypoxemia. Two patients responded to treatment, but the third, who had an antibody highly specific for HLA-DR11, died at 48 hr after transplant. Results of histopathologic studies in this patient are consistent with hyperacute rejection and support a pathogenic role of these antibodies. In contrast, of 86 (93.5%) cases with a negative flow cytometry cross-match, only 4 (5%) had severe but reversible early graft dysfunction with pulmonary infiltrates and hypoxemia, attributed to ischemia-reperfusion injury (P<0.005).

CONCLUSIONS

Class II, and perhaps class I HLA antibodies at relatively low concentrations represent a risk factor for severe early pulmonary graft dysfunction, with the potential to progress to hyperacute rejection and death.

Activator protein-1 (AP-1) is stimulated by microbial superantigens in human monocytic cells

Microbial superantigens bind to major histocompatibility complex (MHC) class II molecules and activate gene transcription in monocytes. In search of transcription factors that potentially mediate the effects of superantigens at the nuclear level, we examined the capacity of staphylococcal superantigens to stimulate the activity of the transcriptional promoter factor activator protein-1 (AP-1). Electrophoretic mobility shift assays showed an increase in nuclear proteins that bound to the consensus AP-1 motif within 5 min following the stimulation of the monocytic cell line THP-1 with toxic shock syndrome toxin-1 (TSST-1) or staphylococcal endotoxin A. We show that mRNA levels for the subunits that compose AP-1, the protooncogenes c-fos and c-jun, are upregulated by stimulation of THP-1 cells with TSST-1. The activated AP-1 complexes were functional, as evidenced by the capacity of TSST-1 to stimulate the expression of an AP-1-driven reporter gene construct transfected into THP-1 cells. These results establish that the engagement of MHC class II molecules by superantigens increases the activity of functional AP-1 complexes and that this may proceed in part by transcriptional activation of c-fos and c-jun protooncogenes.

Signal transduction mechanisms of HLA-DR-mediated interleukin-1 beta production in human monocytes. Role of protein kinase C and tyrosine kinase activation

The signal transduction pathways leading to the expression of IL-1 beta in human monocytes via HLA-DR stimulation were investigated. SEB, a staphylococcal enterotoxin that binds to HLA-DR molecules, induced IL-1 beta expression in human monocytes. Protein synthesis inhibition by cycloheximide did not inhibit SEB-mediated IL-1 beta signal, indicating that protein synthesis is not required for the MHC class-II-mediated IL-1 beta expression. The effect of PKC, PKA, and tyrosine kinase inhibitors on HLA-DR-mediated IL-1 beta mRNA expression was then determined. H7, a preferential PKC inhibitor, completely inhibited IL-1 beta signal induced by SEB. The role of PKC on HLA-DR-mediated IL-1 beta induction was further confirmed by the ability of SEB to activate PKC on monocytes directly when measured with labeled phorbol ester ([3H]Pbt2)-binding capacity of whole cells. HA 1004, a preferential PKA inhibitor, and isobutyl-methyl-xanthine (IBMX), which inhibits the degradation of cAMP, had no effect on SEB-induced IL-1 beta signal, excluding the role of cAMP on HLA-DR-mediated IL-1 beta expression. Two tyrosine kinase inhibitors, genistein and dihydroxycinnamate, both inhibited SEB-induced IL-1 beta mRNA in monocytes. SEB also induced enhanced tyrosine phosphorylation of several proteins in human monocytes when determined with antiphosphotyrosine immunoblotting. Our results demonstrate that both PKC and protein tyrosine kinases are involved in HLA-DR-induced IL-1 beta expression in human monocytes.

The human Fc receptor for mouse IgG2b on monocytes and EBV-B cells is functionally inhibited by anti-HLA class II antibodies

We have recently described a polymorphic Fc receptor for murine IgG2b (mIgG2b), present on human monocytes and EBV-transformed B lymphocytes. The present study shows that anti-HLA class II monoclonal antibody (MoAb) completely inhibits both the (Fc receptor-dependent) T-cell proliferation, induced by mIgG2b anti-CD3 MoAb, and rosetting with mIgG2b-sensitized erythrocytes. This inhibition is also observed with F(ab')2 fragments of anti-HLA class II MoAb, and is therefore not Fc mediated. The Fc receptor for mIgG2b is also present on EBV-transformed B cells obtained from a patient with 'bare lymphocyte syndrome', that completely lack HLA class II antigens. Therefore, the Fc receptor for mIgG2b and HLA class II antigens are not identical. Since the low affinity receptor for IgE (Fc epsilon II; CD23) was reported to be associated at the cell surface with HLA class II antigens, we have compared both types of Fc receptor, and observed that human IgE strongly inhibits the mitogenic effect of murine IgE anti-CD3 but not of mIgG2b anti-CD3 MoAb. We conclude that the human Fc receptor for mIgG2b is strongly inhibited by anti-HLA class II MoAb, but is not identical to HLA class II or Fc epsilon RII.

Signal transduction by HLA class II molecules in human T cells: induction of LFA-1-dependent and independent adhesion

Crosslinking HLA-DR molecules by monoclonal antibodies (moAbs) induces protein tyrosine phosphorylation and results in a secondary elevation of free cytoplasmic calcium concentrations in activated human T cells. Binding of bacterial superantigens or moAbs to DR molecules on activated T cells was recently reported to induce homotypic aggregation through activation of protein kinase C (PKC) and mediated by CD11a/CD54 (LFA-1/CAM-1) adhesion molecules. Here, we report that moAbs directed against framework DR, but neither DR1, 2- and DRw52- nor DQ- and DP-specific moABs induced homotypic aggregation of antigen- and alloantigen-activated T cells, antigen-specific CD4+ T-cell lines, a CD8+ T-cytotoxic cell line, and T-leukemia cells (HUT78). Protein tyrosine kinase (PTK) inhibitor herbimycin A partly blocked class-II-induced aggregation responses. In contrast, phorbol ester (PMA)-induced aggregation was essentially unaffected. A potent inhibitor of PKC, staurosporin, inhibited both moAb- and PMA-induced aggregation responses. The aggregation responses were completely inhibited by low temperatures, cytochalasins B and E, and partly inhibited by EDTA and CD18 moAbs, but unaffected by aphidicolin, mitomycin C, an adenylate cyclase inhibitor (2'5'-dideoxyadenosine), and moAbs against other adhesion molecules (CD2/CD58 [LFA-3], CD28/CD28 ligand B7, CD4, and CD44). In conclusion, HLA class-II-induced aggregation responses in activated T cells appear to involve PTK and PKC activation and to be mediated through CD11a-dependent and independent adhesion pathways.

Interleukin 1 production by human monocytes induced in culture with K562 cells

The effect of neoplastic cells, K562, was evaluated on interleukin 1 (IL-1) production by peripheral blood monocytes of healthy humans. Secretion of the monokine was compared with that resulting from stimulation with bacterial lipopolysaccharide (LPS) or iron particles. In parallel, ability of non-malignant cells to induce production of monocyte-derived IL-1 was tested using allogeneic leukocytes (PBL). The studies were performed using concanavalin A (Con A) thymocyte co-activation assay, applying colorimetric assay of proliferation. The results obtained showed that IL-1 secretion by monocytes took place not only after tumor-cell stimulation, but also in co-cultures with allogeneic PBL. LPS and iron particles, however, were more efficient in stimulating IL-1 production. Absence of IL-1 activity was noted in supernatants of monocyte cultures in the presence of dexamethasone. Supernatants showing IL-1 activity were inactive in the presence of soluble immune response suppressor (SIRS) in IL-1 assay.

Homotypic aggregation of human cell lines by HLA class II-, class Ia- and HLA-G-specific monoclonal antibodies

Major histocompatibility complex (MHC) class II molecules have been implicated in cell adhesion in two ways. In addition to the well-established role of class II antigens in low-affinity adhesion provided by interactions between class II and CD4, recent data indicated that class II may also induce adhesion between T and B cells by activating the CD18/CD11a (LFA-1) adhesion pathway. Here we report that monoclonal antibodies (mAb) against HLA-DR (L243, p4.1, HB10a, VI15) and certain broad class II reacting mAb (TU35, TU39), but not anti-DQ (TU22, Leu-10) mAb, induced homotypic aggregation of human class II-positive monocytic (I937) and T leukemic (HUT78) tumor cell lines and Epstein-Barr virus (EBV) transformed B-lymphoid cell lines (EBV-LCL). Class II-negative cell lines (U-937 and the EBV-LCL mutant line 616) were not induced to aggregate. An HLA-G-transfected EBV-LCL, 221-AGN, but not the class I-negative parental line, 221, showed homotypic aggregation in response to an HLA-G specific mAb (87G) and a broad reacting class I-specific mAb (IOT2). Both cell lines responded with aggregation to anti-class II mAb (TU35). The anti-class I mAb, W6/32, had no effect on all cell lines tested and two anti-beta 2-microglobulin mAb had variable, weak effects. The aggregation response was an active, temperature-sensitive process which was almost totally abrogated by azide and by cytochalasins B and E, but unaffected by colchicine, EDTA, aphidicolin, actinomycin D and protein tyrosine kinase inhibitors (genistein, herbimycin A). Serine/threonine protein kinase inhibitors (staurosporin, H7) partly inhibited the aggregation responses. There was no strict correlation between induction of aggregation and epitope density. FcR were not involved in the aggregation response, since F(ab')2 fragments of anti-DR mAb, L243, were as effective as the whole antibody. The aggregation was not influenced by mAb against accessory molecules previously shown to be involved directly or indirectly in homotypic aggregation [CD11a (LFA-1)/CD18/CD54 (ICAM-1), CD58 (LFA-3)/CD2, BB1/CD28, CD43, and CD44]. In conclusion, these data provide further evidence that HLA molecules are implicated in a novel, cellular aggregation phenomenon involving the cytoskeleton.

Effects of granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-2, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and IL-6 on the production of immunoreactive IL-1 and TNF-alpha by human monocytes

The effects of GM-CSF, IL-2, IFN-gamma, TNF-alpha and IL-6 on the production of IL-1 (both secreted and cell associated) and TNF-alpha by peripheral blood monocytes were studied. Monocytes were cultured for 20 h in suspension and in serum-free conditions which minimized background stimulation of monokine production. GM-CSF, IL-2 and TNF-alpha directly induced the production of cell-associated IL-1 but little or no IL-1 or TNF-alpha secretion. Combination of GM-CSF with IFN-gamma, IL-2 or TNF-alpha synergistically enhanced IL-1 secretion and had an additive effect on cell-associated IL-1 production. Combination of IL-2 with IFN-gamma or TNF-alpha also synergistically enhanced IL-1 secretion but the effect on cell-associated IL-1 production was less than additive. GM-CSF synergistically enhanced TNF-alpha secretion induced by IFN-gamma but not by lipopolysaccharide. GM-CSF did not enhance TNF-alpha secretion induced by IL-2 or TNF-alpha. In contrast, IL-2 synergistically enhanced TNF-alpha secretion induced by IFN-gamma. These results are discussed in relation to cytokine involvement in rheumatoid arthritis.

Monocyte function in IDDM patients and healthy individuals

Interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF-alpha) may be pathogenetically important in insulin-dependent diabetes mellitus (IDDM), which is associated with genes of the HLA region. Since a regulatory role of HLA region genes on monokine production may exist, we looked for an association between the monokine and prostaglandin E2 (PGE2) responses of monocytes (Mo) from 20 healthy males (18-50 years) with HLA-DR types relevant for IDDM susceptibility and resistance (DR1,2, DR1,3, DR1,4, DR3,4). Monokine assays were established and evaluated and the secretions of IL-1 beta, TNF-alpha, and PGE2 measured in Mo cultures (2h, 6h, 20h) prepared by endotoxin-free techniques and stimulated by low-dose E. coli lipopolysaccharides (LPS). There were no significant associations between Mo responses and HLA-DR phenotype. Likewise, Mo from DR2 (n = 5) and DR4 (n = 5) homozygous healthy males demonstrated no significant differences in monokine and PGE2 responses of Mo. In the HLA class III region a diallelic TNF-beta gene NcoI polymorphism consisting of alleles of 5.5 kb and 10.5 kb was recently described and associated with susceptibility to autoimmune diseases including IDDM. We report that IL-1 beta and TNF-alpha responses of Mo from TNF-beta 10.5 kb homozygous healthy individuals were significantly higher than for TNF-beta 5.5/10.5 kb heterozygotes. IL-1 beta and TNF-alpha responses of Mo from males (18-35 years) with newly diagnosed (n = 10) and long-standing IDDM (n = 10) and from age- and HLA-DR-matched healthy males (n = 10) were studied. LPS, gamma interferon (IFN), and TNF-alpha-stimulated Mo cultures were investigated. No significant differences were found between Mo responses of IDDM patients and controls. IFN (1000 U/ml) in the presence of LPS significantly potentiated LPS-stimulated Mo TNF-alpha secretion and reduced the levels of IL-1 beta immunoreactivity in Mo lysates. IFN and TNF-alpha did not have any effects on LPS-stimulated Mo secretion of IL-1 beta immunoreactivity. We conclude that Mo IL-1 beta and TNF-alpha production is normal in patients with recent-onset and long-standing IDDM. The interindividual differences in monokine responses may be accounted for by the diallelic human TNF-beta gene polymorphism rather than by HLA class II genes. This observation may be important for understanding the association of certain HLA haplotypes with autoimmune phenomena and disease.

Human peripheral blood-derived dendritic cells do not produce interleukin 1 alpha, interleukin 1 beta, or interleukin 6

Little is known about the non-antigen-specific signals delivered to T cells by dendritic cells (DC). Because several monocyte-derived factors like interleukins 1 alpha, 1 beta, and 6 (IL-1 alpha, IL-1 beta, and IL-6) enhance the T-cell proliferative responses, we studied the production of the above-mentioned cytokines by DC separated from human peripheral blood. The intracellular expression of the proteins (IL-1 alpha and IL-6) was studied at a single-cell level using an immunolabelling technique. The supernatants and cell lysates were studied with ELISA (IL-1 alpha and IL-1 beta). Northern blotting analysis was used to quantitate the mRNA levels. Several approaches were taken to stimulate the production of IL-1 alpha, IL-1 beta, and IL-6 by DC. These included the incubation of the DC in the presence of either LPS, rIL-1, or monoclonal anti-HLA-DR antibody, or the stimulation of cells with resting allogeneic T cells. None of the stimuli was able to induce the production of IL-1 alpha, IL-1 beta, or IL-6 by DC, whereas LPS-stimulated monocytes were strong producers of these mentioned cytokines and expressed the respective mRNA. Thus we concluded that IL-1 alpha, IL-1 beta, and IL-6 are primarily monocyte-derived factors and that these factors are not needed or produced during the activation of resting T cells by DC.