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Infiltration of eosinophils into the airways plays a central role in the pathophysiology of asthma. Human blood eosinophils express apoptosis-inducing receptors (e.g. CD95R and CD69R) regulating both viability and survival and, thus, the extent of eosinophil infiltration into the airways. Signal transduction processes induced by occupation of the CD69 receptor expressed by eosinophils are insufficiently known. Purified human peripheral blood eosinophils (MACS, purity > 99%) were pre-incubated with a GM-CSF for 18 h and stimulated with alpha-CD69mAb (clon TP1/55), alpha-CD95mAb (clon CH-11), and as a control alpha-CD11bmAb (clon Bear-1). The specificity of receptor ligation was assessed using a blocking mAb (Klon ZB4). Phenotype, viability, apoptosis and bcl-2-expression were measured employing flow cytometry. alpha-CD95mAb (1 microgram/ml) induced apoptosis both in control and GM-CSF (10 ng/ml) treated eosinophils. Similarly, alpha-CD69mAb (10 micrograms/ml) induced apoptosis of GM-CSF-stimulated CD69+ cells after an incubation period of 114 h which was not affected by a CD95 blocking mAb. Naive eosinophils showed a basale, bcl-2-expression, which decreased to 30% after 66 h. In the presence of GM-CSF, intracellular bcl-2-concentration remained unchanged. Following stimulation with alpha-CD69mAb or alpha-CD95mAb, a dose-dependent decline of the bcl-2-expression was detected, whereas alpha-CD11bmAb (10 micrograms/ml) had no effect. The data suggest that both CD95R- and CD69R-induced apoptosis of human eosinophils involves a bcl-2-dependent signal transduction mechanism.

Aim of the Study: To investigate the long-term effect of TNFR55-IgG1 in patients with severe rheumatoid arthritis refractory to multiple previous DMARD treatments., Methods: Between 1994 and 1995 we recruited 80 patients for two double blind, placebo-controlled multicenter trials. All patients were treated for 2-30 months with a glycosylated fused protein consisting of two human p55 TNF receptors linked to a human IgG1-Fc. The dose range was 2.5-100 mg/month given i.v. with cumulative doses from 40-940 mg. All patients were followed-up prospectively for 24-36 months after initiation of therapy. The evaluations included a 48 swollen and tender joint count, ESR. CRP, RF, ANA, ENA, and safety parameters at 6 month intervals. In addition, pharmacokinetics, TNF, and anti-TNFR55-IgG1 antibody levels were available after the first and third injection., Results: Data from 80 patients are available representing an experience of more than 170 patient years; 11 patients are still being treated. Predominant reasons for treatment withdrawal were restrictions in treatment protocol. Six patients died (1 during treatment, 5 in the post-treatment follow-up). All deaths were related to preexisting cardiovascular disease except one post-surgery septic arthritis 6 months after the last dosing (during vacation in another country). No malignancies were detected. Anti-TNFR55-IgG1 antibodies correlated with a decrease in drug half-time. Shifts in the TNFR55-IgG1 glycosylation pattern affected pharmacokinetics and efficacy. A lupus nephritis occurred 18 months after the last dosing in one patient with erosive RA (ANA and dsDNS positive already before TNFR55-IgG1 initiation). Continued treatment for 3 years in 11 patients resulted in an 81% reduction in swollen joint count, less morning stiffness, less pain, and a reduction in steroids., Conclusion: Treatment with TNFR55-IgG1 is safe and efficacious over the long-term in patients with severe refractory RA.

Unlabelled: AIM OF STUDIES: To determine the optimal dose regimen for i.v. TNFR55-IgG1 in refractory rheumatoid arthritis., Methods: 218 patients with refractory rheumatoid arthritis were enrolled for two double-blind placebo-controlled multicenter trials (Europe and USA). They were treated with monthly i.v. placebo, 0.01, 0.05, 0.1 or 0.5 mg/kg TNFR55-IgG1 after a 4 week wash-out of DMARDs. An additional German trial compared biweekly i.v. 20 mg TNFR55-IgG1 and monthly 50 mg following a loading does of 100 mg in 60 patients., Results: TNFR55-IgG1 induced a substantial improvement already apparent one day after the first infusion. A maximal, dose dependent effect was reached after two weeks. Later, efficacy declined in parallel to an increase in anti-TNFR55-IgG1 antibodies resulting in an increased drug clearance. The drug was well tolerated with predominantly mild or moderate adverse events., Conclusion: Intravenous TNFR55-IgG1 was well tolerated and effective in refractory rheumatoid arthritis but the treatment schedules tested could not stabilise the initial improvement.

The expression of B7-1/2 molecules in addition to TAA in APC significantly improves the generation of specific CTL in vitro. Moreover, human fibroblasts, usually devoid of APC capacity, can be engineered into effective APC upon infection with recVV encoding costimulatory molecules together with specific epitopes. The generation of artificial APC by infection of non professional APC with appropriately engineered recVV is a new concept that may be useful in the implementation of immunotherapy strategies.

Aims and Methods: While CD40 is a costimulatory molecule of utmost importance for B-cell proliferation and Ig class switch its role has not been elucidated in the human thymus and in thymic epithelial tumors. To investigate, whether CD40 is functionally active there, we investigated the proliferative response by 3H-Thymidin incorporation of primary normal and neoplastic thymic epithelial cell cultures to CD40 triggering by soluble CD40 ligand (CD40L)., Results: Normal thymic epithelial cells exhibited proliferation in response to CD40 ligand in a dose dependent manner, while a CD40 ligand specific monoclonal antibody prevented this effect. This response was not significantly different from the response of neoplastic thymic epithelial cells derived from myasthenia gravis-associated thymomas., Conclusion: Our data demonstrate that CD40 is expressed on the surface of normal and neoplastic epithelial cells of the thymus and is a functional molecule in terms of epithelial cell proliferation in vitro. Given the differential expression of CD40 in the various histological thymoma subtypes in vivo, the finding suggests a role of CD40 in the different mechanisms of tolerance breakdown in thymomas.

Hyperacute graft rejection triggered by the activation of the recipient's complement system represents the major obstacle to a successful xenotransplantation. Inhibition of complement activation is, therefore, considered as a prerequisite for xenograft survival. Support of the physiological regulation of the complement system appears to be the most promising strategy as indicated by first results from animal xenograft experiments. The transfer of human membrane-bound complement regulatory proteins offers new chances to protect the xenograft against the cytolytic complement attack. Another approach aims at interfering with receptor/ligand interaction of the adhesion molecules CR3 and CR4 (CD11b,c/CD18). All strategies of complement intervention have to consider the important function of complement within the immunological defense.

Common variable immunodeficiency (CVI) is widely believed to involve a primary B cell defect, however, there is increasing evidence of T cell dysfunction in these patients. To test the hypothesis that B cells of patients with CVI are not defective, we investigated whether immunoglobulin production can be induced by activation through the CD40 system. Our results show that 6 of 7 children with CVI produced IgG when B cells were activated through CD40 plus IL-10. In most patients, IgM and IgA production were also induced. However, we could demonstrate that failure of immunoglobulin production was not due to a defective CD40 ligand expression on T cells. Taken together, our data show that B cells of patients with CVI are functionally normal when activated through CD40 plus IL-10. IL-10 seems to be more effective than IL-2 in restoration of immunoglobulin production in such patients.

The knowledge about molecular mechanisms of endotoxin (LPS) recognition by cellular receptor CD14 and its consequences as well as the relationship between soluble and membrane-bound receptor is reviewed. The binding of endotoxins to membrane-bound CD14 is mediated by special so-called LPS-binding serum proteins. The mechanism of signal transduction is not yet known. After activation by LPS, monocytes produce free oxygen radicals, IL-1, IL-6, TNF alpha and other mediators. CD14 is present in normal serum as soluble receptor which can neutralize endotoxins in respect to their monocyte activating capacity.

Fc gamma receptors are a group of three different receptors with several subtypes. They are widely distributed on many cells of the immune system and contribute to the pathogenesis of immune complex- and autoantibody-mediated diseases such as vasculitis, rheumatoid arthritis, idiopathic thrombocytopenic purpura or autoimmune neutropenia. This review focuses on the structure, distribution and function in Fc gamma receptors and their subtypes.

APO-1 is a 48kDa transmembrane glycoprotein and belongs to the NGF/TNF receptor family of surface molecules. Cross-linking of APO-1 induces apoptotic cell death in sensitive cells. Here we show that APO-1 is an activation molecule on B cells. It could be induced/enhanced on dense and buoyant tonsillar B cells, respectively, through surface immunoglobulin cross-linking in combination with interleukin-2 or by interferon-gamma together with tumor necrosis factor-alpha. These conditions also increased the amount of intercellular adhesion molecule-1 (ICAM-1; CD54) on these cells. Epstein-Barr virus transformants of peripheral B cells co-expressed APO-1 and CD54 at very high levels. Immunohistologically, APO-1 was detectable at low levels in a subpopulation of follicular center B blasts and, at higher levels, in sinusoidal B cells. APO-1 was undetectable in follicular mantle B cells and plasma cells. Neoplastic B cell essentially mimicked their reactive counterpart with regard to APO-1 and CD54 expression.