Functional disparity of distinct CD28 response elements toward mitogenic responses

Activation of T cells through the antigen-specific T-cell receptor in combination with a costimulatory signal results in efficient cytokine gene transcription. The CD28-induced signal represents a major costimulatory signal for T cells. A CD28 response element, named CD28RE, was first identified in the interleukin-2 (IL-2) promoter region. Here we demonstrate that the NF-kappaB sequence in the IL-6 promoter functions as a CD28 response element. Mutations in this sequence rendered the IL-6 promoter unresponsive to CD28 costimulation. Moreover, this element could replace the IL-2 CD28RE in conferring CD28 responsiveness to the IL-2 promoter. In analogy to the known CD28 response elements IL-2 CD28RE, IL-8 CD28RE, and the human immunodeficiency virus-1 (HIV-1) NF-kappaB motif, the IL-6 NF-kappaB motif efficiently bound c-Rel, c-Rel/NFKB1, and the recently identified inducible T-cell factor NF-MATp35. However, the IL-6 NF-kappaB sequence together with the IL-8 CD28RE and HIV-1 NF-kappaB sequence differed from the IL-2 CD28RE in the binding of NF-kappaB/Rel family proteins. Although the IL-2 CD28RE exerted selective binding with c-Rel and c-Rel/NFKB1, the other CD28REs allowed efficient binding of a wide range of NF-kappaB/Rel family proteins. The difference in binding specificity correlated with the capacity of the distinct CD28 response elements to function in the context of the IL-6 promoter in response to T-cell activation. Domain swapping experiments revealed that the IL-8 CD28RE and HIV-1 NF-kappaB motif conferred similar responsiveness as the genuine IL-6 NF-kappaB motif in the transcriptional activation of the IL-6 promoter upon CD28 costimulation. In contrast, replacement of the IL-6 NF-kappaB sequence by the IL-2 CD28RE motif strongly reduced the responsiveness of the IL-6 promoter. These data indicate that despite the sequence similarity, two different classes of CD28 responsive elements exist that differ in their NF-kappaB binding capacity and the ability to confer CD28 costimulatory responsiveness toward a heterologous promoter.

An IL-13 promoter polymorphism associated with increased risk of allergic asthma

IL-13 plays a crucial role in the development of allergic asthma by several mechanisms, including induction of IgE antibodies, airway eosinophilia and hyper-reactivity. We previously established a deregulated production of IL-13 by T cells from allergic asthma patients. In this report we describe the identification of a novel IL-13 promoter polymorphism (C to T exchange) at position -1055. The IL-13 -1055 TT genotype is associated with allergic asthma (P = 0.002), altered regulation of IL-13 production (P < 0.002), and increased binding of nuclear proteins to this region. We postulate that the presence of this polymorphism predisposes to the development of allergic asthma.

A new principle for rapid immunoassay of proteins based on in situ precipitate-enhanced ellipsometry

A new technique is presented that allows measurement of protein concentrations in the picomolar range with an assay time of only 10-20 min. The method is an enzyme-linked immunosorbent assay (ELISA), but uses in-situ ellipsometric measurement of a precipitating enzyme product instead of the usual colorimetric detection of accumulating enzyme product in solution. Quantitative validation was obtained by use of annexin V, a protein with high binding affinity for phosphatidylserine-containing phospholipid membranes, resulting in a transport-limited adsorption rate. This property was exploited to obtain a range of low surface concentrations of annexin V by timed exposures of phospholipid bilayers to known concentrations of annexin V. Using polyvinylchloride (PVC)-coated and silanized silicon slides, various versions of this technique were used for the rapid assay of fatty acid-binding protein (FABP), a recently introduced early marker for acute myocardial infarction with a normal plasma concentration below 1 nmol/l, interleukin 6 (IL-6), a cytokine with normal plasma concentrations below 1 pmol/l, and again, annexin V. A possible future application of the method in the development of a one-step ELISA is discussed.

Patients with systemic lupus erythematosus with high plasma levels of sFas risk relapse

OBJECTIVE

We related soluble Fas (sFas) levels to the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) in a longitudinal series of plasma samples of patients with SLE to evaluate the relation between excessive production of sFas and disease activity.

METHODS

We generated 21 monoclonal antibodies against Fas. Two of these were used to develop and validate a sensitive sandwich ELISA for the longitudinal analysis of sFas levels in plasma of 30 patients and 25 controls.

RESULTS

At the start of followup, a significant elevation (p<0.0001) was found in sFas levels in SLE (1167+/-347 pg/ml sFas) compared to controls (618+/-98 pg/ml sFas). Also, at the start of the followup a significant difference (p = 0.0028) existed between patients who were going to have a relapse (1236+/-402 pg/ml sFas) during followup and patients who were not (809+/-276 pg/ml sFas). While sFas did not fluctuate with disease activity in individual patients, we found a strong correlation (r = 0.75, p<0.0001) between sFas and SLEDAI, but only at the time of relapse, when we analyzed the patients as a group.

CONCLUSION

In individual patients with SLE, sFas does not fluctuate with disease activity. However, patients with high plasma levels of sFas are at risk of relapse.

Histamine inhibits the production of interleukin-12 through interaction with H2 receptors

IL-12 is essential for T helper 1 (Th1) development and inhibits the induction of Th2 responses. Atopic diseases, which are characterized by Th2 responses, are associated with the overproduction of histamine. Here we present evidence that histamine, at physiological concentrations, strongly inhibits human IL-12 p40 and p70 mRNA and protein production by human monocytes. The use of specific histamine receptor antagonists reveals that this inhibition is mediated via the H2 receptor and induction of intracellular cAMP. The inhibition of IL-12 production is independent of IL-10 and IFN-gamma. The observation that histamine strongly reduces the production of the Th1-inducing cytokine IL-12 implies a positive feedback mechanism for the development of Th2 responses in atopic patients.

Human intravenous immunoglobulin (IVIG) preparations degranulate human neutrophils in vitro

IVIG preparations have biological effects in vivo that are not fully understood. Possible effects include the property to stimulate Fc receptors on various cell types. To study whether IVIG may interact with neutrophils we developed an in vitro system, in which neutrophils, in whole blood or purified, were incubated with IVIG and assessed for degranulation by measuring the release of elastase and lactoferrin in culture medium. All commercially available IVIG preparations tested induced degranulation of neutrophils when incubated for 2 h at therapeutically relevant concentrations. In studies with blocking antibodies against Fc receptors (FcR), this degranulation was shown to be dependent on Fc gammaRII, whereas Fc gammaRIII had no effect. Experiments with purified neutrophils as well as binding experiments with labelled IVIG preparations indicated that neutrophil degranulation resulted from a direct interaction of IVIG with neutrophils. Using gel filtration fractions, it was found that polymeric and dimeric IgG present in IVIG was mainly responsible for the degranulation. We suggest that degranulation of neutrophils may contribute to the (side)effects of IVIG treatment in vivo.

Blocking interleukin-6 activity with chimeric anti-IL6 monoclonal antibodies in multiple myeloma: effects on soluble IL6 receptor and soluble gp130

Interleukin-6 (IL6) plays a major role in the pathogenesis of multiple myeloma. In patients with monoclonal gammopathy serum levels of sIL6R have been found to be increased. The role of IL6 in the regulation of soluble receptors is still unclear. In a phase I/II study we treated 12 myeloma patients with high-affinity chimeric anti-IL6 monoclonal antibodies. This treatment resulted in a total in vivo blockage of IL6 activity and as a result we had an unique opportunity to gain insight into the possible regulation effects of IL6 on these soluble IL6 receptors. Pre-treatment sIL6R levels were elevated in 9 of the 12 patients; pre-treatment sgp130 levels were significantly increased in all patients. Total blockage of IL6 activity by the high-affinity cMab did not influence sIL6R in 10 of these 12 patients and sgp130 levels remained stable in all patients. Of the 2 patients whose sIL6R levels increased during therapy, one had progressive disease and the other developed an acute infection. We conclude that in most end-stage myeloma patients sIL6R and sgp130 serum levels are elevated, but that there is no relation between IL6 activity and sIL6R or sgp130 levels.

Do elevated levels of serum-soluble fas contribute to the persistence of activated lymphocytes in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is characterized by generalized immune activation. Part of this might be explained by a decreased rate of apoptosis, possibly related to elevated levels of soluble Fas (sFas) which can inhibit Fas mediated apoptosis of lymphocytes. In order to substantiate the relation between levels of sFas and lymphocyte activation in SLE we monitored sFas levels, lymphocyte activation and disease activity in 25 SLE patients. SLEDAI scores were registered and sera were assayed for sFas levels by an enzyme-linked immunosorbent assay. Flow cytometry was used to monitor the state of activation of lymphocyte subsets. Eighteen healthy, age-matched volunteers served as controls. Soluble Fas levels were elevated in SLE patients (n=25) compared to healthy controls (n=18, P=0.002). Soluble Fas levels correlated with SLEDAI scores (r=0.45, P=0.02). Levels of sFas correlated with the percentages of activated B cells defined as CD20(+)CD38(+) cells (r=0.47, P=0.009). Percentages of CD20(+)CD38(+) cells were increased in quiescent SLE compared to healthy controls (P=0.003). The expression of activation markers on CD4(+) T lymphocytes (IL-2R, P=0.04; HLA-DR, P=0.01) and CD8(+) T lymphocytes (HLA-DR, P=0.007) was also increased in quiescent SLE compared to controls. Activation markers on all lymphocyte subsets tended to increase further during disease activity. No correlation was observed between percentages of activated T lymphocyte subsets and levels of sFas. In conclusion, soluble Fas levels are increased in SLE patients and correlate with disease activity as measured by the SLEDAI score and B and T cell subsets are activated even during quiescent SLE. Serum levels of sFas correlate with percentages of activated B cells but not with that of activated T cells.

Chimaeric anti-interleukin 6 monoclonal antibodies in the treatment of advanced multiple myeloma: a phase I dose-escalating study

Interleukin 6 plays a key role in the pathogenesis of multiple myeloma (MM). Therefore we conducted a phase I dose-escalating study with chimaeric monoclonal anti-IL6 antibodies (cMab) in MM patients resistant to second-line chemotherapy. The cMab (CLB IL6/8; Kd 6.25 x 10(-12)M) was given in two cycles of 14 daily infusions, starting on day 1 and day 28, repectively, with a daily dose of 5 mg in patients 1-3, 10 mg in patients 4-6, 20 mg in patients 7-9 and 40mg in patients 10-12 (total dose 140 mg, 280mg, 560 mg and 1120 mg of anti-IL6, respectively). 11/12 patients had elevated pretreatment IL6 levels. Except for transient thrombocytopenia in two patients there was no toxicity. There were no changes in haemoglobin levels, granulocyte count, liver enzymes or renal function. No human anti-chimaeric antibodies were induced. This was also reflected in a long half-life time of the cMab (median 17.8 d), resulting in accumulation of the anti-IL6 cMab and high levels of circulating IL6. However, this was in the form of biologically inactive IL6/cMab complexes and did not result in acceleration of the disease. Although C-reactive protein (CRP) levels were decreased to below detection level in 11/12 patients, indicating effective IL6 blocking, none of the patients achieved a response according to the standard criteria. We conclude that this chimaeric anti-IL6 Mab has a low toxicity, low immunogenicity and a long T1/2. A dose of 40 mg/d for 14 d can safely be used in future phase II studies.

Human chromosome 21 determines growth factor dependence in human/mouse B-cell hybridomas

Interleukin 6 (IL-6) serves as a growth factor for mouse plasmacytomas. As a model for IL-6-mediated growth of plasmacytomas, we study IL-6-dependent B-cell hybridomas, which can be generated through fusion of B lymphocytes with a plasmacytoma cell line, e.g., SP2/0. In the present report, we have investigated the peculiar behavior of B-cell hybridomas with respect to IL-6 dependence. We demonstrate that although newly generated hybridomas are IL-6 dependent, many hybridomas lose this dependency at frequencies as high as 50%, shortly after fusion. We speculated that the loss of IL-6-dependent growth is due to the well-known chromosomal instability of B-cell hybridomas. Consequently, loss of IL-6 dependence is the result of loss of a specific chromosome(s). This model implies the existence of an "IL-6 dependency" gene, the loss of which makes hybridomas capable of proliferating in the absence of IL-6. Because SP2/0 is IL-6 independent, the IL-6-dependent phenotype of B-cell hybridomas, and hence the IL-6 dependency gene, must be derived from the B lymphocyte. We have tested this model by generating human/mouse B-cell hybridomas through fusion of human B lymphocytes with SP2/0. We then analyzed the human chromosome content of 10 IL-6-dependent and 14 IL-6-independent subclones. From that analysis we concluded that the presence of human chromosome 21 correlated with IL-6 dependence. This correlation was confirmed by microcell fusion experiments in which a single copy of chromosome 21 was introduced into IL-6-independent hybridomas, resulting in reconstitution of the IL-6-dependent phenotype. We therefore conclude that chromosome 21 carries an IL-6 dependency gene.

Type 1- and type 2-like lesional skin-derived Mycobacterium leprae-responsive T cell clones are characterized by coexpression of IFN-gamma/TNF-alpha and IL-4/IL-5/IL-13, respectively

In an earlier study, we generated a large number of Mycobacterium leprae-responsive and M. leprae-nonresponsive T cell clones (TCC) from the lesional skin of immunologic unstable borderline leprosy patients. In that study, we divided TCC into type 1- and type 2-like on the basis of their IFN-gamma and IL-4 expression. To explore whether other cytokines are coproduced along with IFN-gamma and IL-4, we investigated the secretion of a panel of other cytokines (TNF-alpha, IL-5, IL-6, IL-10, and IL-13) by a large number of these TCC. Upon analysis of 139 M. leprae-responsive TCC, we observed a positive correlation in the coproduction of IFN-gamma/TNF-alpha (r = 0.81), and in that of IL-4/IL-5 (r = 0.83), IL-4/IL-13 (r = 0.80), and IL-5/IL-13 (r = 0.82). Polarized type 1-like TCC produced dominantly IFN-gamma/TNF-alpha, and polarized type 2-like TCC predominantly IL-4/IL-5/IL-13. Most type 0-like TCC produced both sets of cytokines. In contrast, type 1- and type 2-like subsets of M. leprae-nonresponsive TCC (n = 58) did not show the same coexpression of these cytokines. Furthermore, when the differential expression of a broad panel of cytokines by individual M. leprae-responsive TCC is considered, it appeared that additional phenotypes could be recognized. These results suggested that distinct isotypes of type 1- and type 2-like T cells, based on the secretion of a panel of cytokines, may reflect M. leprae-specific characteristics.

The role of IL-13 in IgE synthesis by allergic asthma patients

IgE antibodies play a crucial role in allergic type I reactions. Only IL-4 and IL-13 are able to induce an immunoglobulin isotype switch to IgE in B cells. A major question is to what extent these cytokines contribute to the production of IgE in allergic patients. To address this question we used an in vitro culture system in which the production of IgE is dependent on endogenously produced IL-4 and IL-13. In cultures of purified T and B cells from allergic asthma patients and non-atopic controls, T cells were polyclonally stimulated to obtain IL-4, IL-13 and subsequently IgE secretion. The absolute amount of IgE produced was not significantly different between patients and controls. When neutralizing IL-4 antibodies were included during culture, the production of IgE was dramatically inhibited in both patients and controls (production of IgE was reduced to 12%). However, neutralization of IL-13 led to a significantly stronger inhibition of IgE production in the patient group: production of IgE was reduced to 23 +/- 3% versus 50 +/- 10% in the control group. Corresponding with these results, we also observed a higher production of IL-13 by the patients, while the production of IL-4 was not significantly different. A more detailed analysis of the production of IL-13 revealed that patients' T cells were less sensitive to a negative signal controlling IL-13 production. Our results indicate that, at least in vitro, IgE production in allergic asthma patients is more dependent on IL-13 than in non-atopics, due to enhanced IL-13 production and to enhanced IgE production in response to IL-13.

Cytokine production in whole blood cell cultures of patients with rheumatoid arthritis

OBJECTIVE

The measurement of cytokine production of activated lymphocytes and monocytes in the whole blood cell (WBC) culture system may provide a sensitive tool for evaluating the actual ongoing immune response of patients with rheumatoid arthritis (RA).

METHODS

Lipopolysaccharide (LPS) up to 250 pg/ml was used for the stimulation of monocytes for measuring the production of tumour necrosis factor alpha (TNF alpha), interleukin 6 (IL6) and IL12, while the anti-CD3 (1 microgram/ml) and anti-CD28 (5 micrograms/ml) combination was used for T cell stimulation with the measuring of IL4 and interferon gamma (INF gamma) production. Twenty seven patients with RA and 23 healthy controls were studied.

RESULTS

The results showed a decreased IL6 (LPS stimulus 4-6 pg/ml) and IL-12 (LPS stimulus 16-62 pg/ml) production in the RA patients. The maximal production of both cytokines was comparable with the normal controls. T cell stimulation showed a significant decreased INF gamma production in the RA patients.

CONCLUSIONS

These findings obtained in the WBC culture system are highly suggestive for a decreased TH-1 derived cytokine production by a diminished IL12 production in RA patients. Another possibility is that both IL12 and INF gamma production in WBCs are inhibited by eventual circulating serum factors.

Modulation of chronic excessive interleukin-6 production in multiple myeloma does not affect thyroid hormone concentrations

Interleukin-6 (IL6) is believed to be involved in alterations of thyroid hormone metabolism in acute nonthyroidal illness. To evaluate the effects of IL6 on thyroid hormone metabolism in a chronic IL6-mediated disease, we measured thyroid hormone concentrations in multiple myeloma patients treated with intravenous anti-IL6 chimeric monoclonal antibodies ([cMabs] Kd = 6.25 x 10(-12) mol/L). Twelve patients were studied, receiving at least one complete treatment cycle of 14 days (daily dose: 5 mg, n = 3; 10 mg, n = 3; 20 mg, n = 3; and 40 mg, n = 3). Eight of them also completed a second treatment cycle of 14 days. Thyroid hormone concentrations were measured before, during, and after treatment with the anti-IL6 cMab. Even in the group with the lowest dosage, IL6 activity measured by the B9 bioassay was blocked completely. Compared with the reference ranges, 10 of 12 patients had one or more abnormal pretreatment values for thyroid hormone concentrations. Thyroid autoantibodies were negative in all patients. There was no correlation between thyroid hormone concentrations and IL6 levels, although plasma IL6 levels were increased in all but one subject. Moreover, neutralization of free IL6 by the anti-IL6 cMab did not affect thyroid hormone concentrations, although IL6-dependent C-reactive protein (CRP) levels decreased to undetectable levels in 11 of 12 patients. Two patients developed infectious complications resulting in increased free IL6 and CRP levels and in profound alterations of thyroid hormone levels consistent with an acute euthyroid sick syndrome. We conclude that IL6 is not a major determinant of thyroid hormone abnormalities in a chronic disease like multiple myeloma, but IL6 may be involved in thyroid hormone metabolism in acute diseases (probably in combination with other factors).

Reduced production of IL-12 and IL-12-dependent IFN-gamma release in patients with allergic asthma

In atopic patients, allergen-specific T cells have acquired the Th2 phenotype, which is considered to be responsible for the class switch to IgE Ab formation. Because IL-12 is a key cytokine for the induction of Th1 responses, a reduced capacity to produce this cytokine could lead to aberrant Th2 development. Therefore, we examined the production of IL-12 in whole blood cultures from patients with allergic asthma (n = 15) in comparison with nonatopic control subjects (n = 15) to different stimuli. After stimulation with Staphylococcus aureus Cowan I strain (SAC) we observed a 2.6-fold reduction of IL-12 p70 production in the patient group (p < 0.005). This was not due to a general failure of monocytes from these patients to produce cytokines, because the production of IL-6 was normal. SAC also induced the production of IFN-gamma, which was blocked by neutralization of IL-12. In line with the reduced levels of IL-12 secretion, the patient group showed a 3-fold reduction of IL-12-dependent IFN-gamma production (p < 0.005). The amounts of IL-12 and IFN-gamma were positively correlated in both the patient (R = 0.51 at 0.05% SAC and R = 0.64 at 0.01% SAC) and the control groups (R = 0.64 at 0.05% SAC and R = 0.70 at 0.01% SAC). The IFN-gamma:IL-12 ratio was not different between patients and control subjects, indicating a normal response to IL-12. Diminished production of IL-12 and IFN-gamma could not be explained by an increased production of IL-10, because in SAC-stimulated cultures IL-10 was hardly induced in both groups. Furthermore, after stimulation with Escherichia coli, the production of IL-10 was similar in patients and control subjects.

Reduced production of IL-12 and IL-12-dependent IFN-gamma release in patients with allergic asthma

In atopic patients, allergen-specific T cells have acquired the Th2 phenotype, which is considered to be responsible for the class switch to IgE Ab formation. Because IL-12 is a key cytokine for the induction of Th1 responses, a reduced capacity to produce this cytokine could lead to aberrant Th2 development. Therefore, we examined the production of IL-12 in whole blood cultures from patients with allergic asthma (n = 15) in comparison with nonatopic control subjects (n = 15) to different stimuli. After stimulation with Staphylococcus aureus Cowan I strain (SAC) we observed a 2.6-fold reduction of IL-12 p70 production in the patient group (p &lt; 0.005). This was not due to a general failure of monocytes from these patients to produce cytokines, because the production of IL-6 was normal. SAC also induced the production of IFN-gamma, which was blocked by neutralization of IL-12. In line with the reduced levels of IL-12 secretion, the patient group showed a 3-fold reduction of IL-12-dependent IFN-gamma production (p &lt; 0.005). The amounts of IL-12 and IFN-gamma were positively correlated in both the patient (R = 0.51 at 0.05% SAC and R = 0.64 at 0.01% SAC) and the control groups (R = 0.64 at 0.05% SAC and R = 0.70 at 0.01% SAC). The IFN-gamma:IL-12 ratio was not different between patients and control subjects, indicating a normal response to IL-12. Diminished production of IL-12 and IFN-gamma could not be explained by an increased production of IL-10, because in SAC-stimulated cultures IL-10 was hardly induced in both groups. Furthermore, after stimulation with Escherichia coli, the production of IL-10 was similar in patients and control subjects.

Identification of residues in the putative 5th helical region of human interleukin-6, important for activation of the IL-6 signal transducer, gp130

We have previously shown that L58 in the putative 5th helical region of human interleukin-6 (IL-6) is important for activation of the IL-6 signal transducer gp130 [de Hon et al. (1995) FEBS Lett. 369, 187-191]. To further explore the importance of individual residues in this region for gp130 activation we have now combined Ala substitutions of residues E52, S53, S54, K55, E56, L58 and E60 with other substitutions in IL-6, known to affect gp130 activation (Q160E and T163P). The combination mutant protein with L58A completely lost the capacity to induce the proliferation of XG-1 myeloma cells, and could effectively antagonize wild type IL-6 activity on these cells. Moreover, the data suggest that besides L58, S54 particularly, but also E52, S53, K55 and E56 contribute to gp130 activation.

Endogenous interleukin 6 production in multiple myeloma patients treated with chimeric monoclonal anti-IL6 antibodies indicates the existence of a positive feed-back loop

In vitro as well as in vivo observations have shown that IL6 plays a key role in the pathogenesis of multiple myeloma. Therefore we started a phase I/II dose escalating study with chimeric monoclonal anti-IL6 antibodies (cMab) in multiple myeloma (MM) patients resistant to second-line chemotherapy. Here we describe the pharmacological data as well as a new method for calculating the endogenous IL6 production. The cMab (CLB IL6/8; Kd: 6.25 x 10(-12) M) was given in two cycles of 14 daily infusions, starting on day 1 and day 28. Daily dose: 5 mg in patients 1-3, 10 mg in patients 4-6, and 20 mg in patients 7-9 (total dose 140, 280, and 560 mg of anti-IL6, respectively). Using the pharmacokinetic data of free IL6 and the binding characteristics of the cMab, the endogenous IL6 production could be calculated from day to day using a one-compartment open model. The median half-life time of this antibody was 17.6 d. No human antichimeric antibodies were induced. Pre-treatment median endogenous IL6 production in the MM patients was 60 micrograms/d (range 13.8-230; normal controls < 7 micrograms/d). During treatment with anti-IL6 cMabs, the endogenous IL6 production immediately decreased in all patients to below 3 micrograms/d and never reached the pre-treatment value during the treatment period, except in two patients who developed an active infection, resulting in an IL6 production of 128 and 1,208 micrograms/d, respectively. We concluded that in MM patients endogenous IL6 production is 2-30 times higher than in healthy individuals. The anti-IL6 cMab strongly suppress this endogenous IL6 production, probably by blocking a positive feed-back loop, but this cMab does not prevent infection-induced IL6 production. The chimeric anti-IL6 Mabs have a long half-life time, a low immunogenicity, and are able to block IL6-dependent processes in vivo.

Release of interleukin-12 in experimental Escherichia coli septic shock in baboons: relation to plasma levels of interleukin-10 and interferon-gamma

Interleukin (IL)-12 is thought to be a key factor for the induction of interferon gamma (IFN-gamma), a cytokine essential for the lethal effects of endotoxin. We report here on the release of the nonfunctional subunit of IL-12, p40, as well as biologically active heterodimeric IL-12, p70, after administration of a lethal (n = 5) or sublethal (n = 8) dose of live Escherichia coli to baboons. Remarkably, on lethal challenge, peak levels of p40 were observed at 3 hours that were about twofold lower than those elicited after sublethal challenge (2,813 +/- 515 pg/mL v 4,972 +/- 732 pg/mL, P < .05). This disparity was also observed, although to a lesser extent, for IL-12 p70 antigen, of which maximum levels of 91 +/- 47 pg/mL and 151 +/- 41 pg/mL were measured 6 hours after a lethal or sublethal dose of E coli, respectively. Circulating p70 antigen correlated with IL-12 biologic activity (r = 0.869; P < .001). When comparing lethal to sublethal conditions, lower peak levels of IL-12 on lethal E coli sharply contrasted with higher levels of other proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, IL-1beta, IL-6, and IL-8 observed in these animals. Lower IL-12 concentrations in the lethal group may have resulted in part from the enhanced production of IL-10, a known inhibitor of IL-12 synthesis in vitro, as peak levels of this cytokine 3 hours postchallenge inversely correlated with peak levels of IL-12, in particular p40 (r = -0.802; P < .01). Contrary to what might be expected if IFN-gamma were solely induced by IL-12, lethally challenged baboons generated threefold more IFN-gamma at 6 hours than those receiving a sublethal dose (P < .05). Moreover, higher levels of IFN-gamma were associated with lower p40/p70 ratios, suggesting that, in agreement with observations in vitro, IFN-gamma may have preferentially upregulated the release of p70 over p40. These data show that IL-12 is released in experimental septic shock in nonhuman primates and suggest that IL-10 and IFN-gamma are involved in the regulation of this release. Furthermore, this study indicates that the systemic release of IL-12 might be essential, but is not likely sufficient, to promote lethal production of IFN-gamma in sepsis.

Release of leukemia inhibitory factor in primate sepsis. Analysis of the role of TNF-alpha

Leukemia inhibitory factor (LIF), a pleiotropic cytokine with many biologic effects overlapping with those of IL-6, has been implicated in the pathogenesis of sepsis. We here analyzed the kinetics of LIF in 13 baboons challenged with a lethal (n=6) or sublethal (n=7) dose of Escherichia coli. In addition, to assess the role of TNF-alpha in the induction of LIF in vivo, seven baboons were studied that had either received a bolus injection of recombinant human TNF-alpha (100 micrograms/kg, n=3), or to whom 15 mg/kg of an anti-TNF mAB before lethal E. coli challenge was administered (n=4). LIF levels increased 2 h after E coli challenge, and reached maximum values at 4 and 8 h after a sublethal (4.4 +/- 1.6 ng/ml) or lethal (40.9 +/- 3.8 ng/ml) dose, respectively. TNF-alpha injection induced a modest rise in LIF concentrations, peaking after 6 h (228 +/- 46 pg/ml). Circulating LIF correlated with plasma levels of IL-6, both after E. coli challenge (Spearman Rank coefficient of correlation (r) = 0.849, p&lt;0.001), as well as upon TNF-alpha injection (r=0.863, p&lt;0.001). Moreover, the E. coli-induced release of either cytokine was reduced 6- to 10-fold after pretreatment with anti-TNF mAb, except in one nonsurviving animal, which exhibited a progressive increase of LIF and IL-6 levels despite the absence of TNF immunoreactivity. These results show that TNF-alpha is an intermediate factor in concerted release of LIF and IL-6 in vivo, and indicate that the enhanced elaboration of these cytokines may predict disease outcome in severe sepsis.

Release of leukemia inhibitory factor in primate sepsis. Analysis of the role of TNF-alpha

Leukemia inhibitory factor (LIF), a pleiotropic cytokine with many biologic effects overlapping with those of IL-6, has been implicated in the pathogenesis of sepsis. We here analyzed the kinetics of LIF in 13 baboons challenged with a lethal (n=6) or sublethal (n=7) dose of Escherichia coli. In addition, to assess the role of TNF-alpha in the induction of LIF in vivo, seven baboons were studied that had either received a bolus injection of recombinant human TNF-alpha (100 micrograms/kg, n=3), or to whom 15 mg/kg of an anti-TNF mAB before lethal E. coli challenge was administered (n=4). LIF levels increased 2 h after E coli challenge, and reached maximum values at 4 and 8 h after a sublethal (4.4 +/- 1.6 ng/ml) or lethal (40.9 +/- 3.8 ng/ml) dose, respectively. TNF-alpha injection induced a modest rise in LIF concentrations, peaking after 6 h (228 +/- 46 pg/ml). Circulating LIF correlated with plasma levels of IL-6, both after E. coli challenge (Spearman Rank coefficient of correlation (r) = 0.849, p<0.001), as well as upon TNF-alpha injection (r=0.863, p<0.001). Moreover, the E. coli-induced release of either cytokine was reduced 6- to 10-fold after pretreatment with anti-TNF mAb, except in one nonsurviving animal, which exhibited a progressive increase of LIF and IL-6 levels despite the absence of TNF immunoreactivity. These results show that TNF-alpha is an intermediate factor in concerted release of LIF and IL-6 in vivo, and indicate that the enhanced elaboration of these cytokines may predict disease outcome in severe sepsis.