CD20-Specific Immunoligands Engaging NKG2D Enhance γδ T Cell-Mediated Lysis of Lymphoma Cells.

Human γδ T cells are innate-like T cells which are able to kill a broad range of tumour cells and thus may have potential for cancer immunotherapy. The activating receptor natural killer group 2 member D (NKG2D) plays a key role in regulating immune responses driven by γδ T cells. Here, we explored whether recombinant immunoligands consisting of a CD20 single-chain fragment variable (scFv) linked to a NKG2D ligand, either MHC class I chain-related protein A (MICA) or UL16 binding protein 2 (ULBP2), could be employed to engage γδ T cells for tumour cell killing. The two immunoligands, designated MICA:7D8 and ULBP2:7D8, respectively, enhanced cytotoxicity of ex vivo-expanded γδ T cells against CD20-positive lymphoma cells. Both Vδ1 and Vδ2 γδ T cells were triggered by MICA:7D8 or ULBP2:7D8. Killing of CD20-negative tumour cells was not induced by the immunoligands, indicating their antigen specificity. MICA:7D8 and ULBP2:7D8 acted in a dose-dependent manner and induced cytotoxicity at nanomolar concentrations. Importantly, chronic lymphocytic leukaemia (CLL) cells isolated from patients were sensitized by the two immunoligands for γδ T cell cytotoxicity. In a combination approach, the immunoligands were combined with bromohydrin pyrophosphate (BrHPP), an agonist for Vδ2 γδ T cells, which further enhanced the efficacy in target cell killing. Thus, employing tumour-directed recombinant immunoligands which engage NKG2D may represent an attractive strategy to enhance antitumour cytotoxicity of γδ T cells.

Human kappa light chain targeted Pseudomonas exotoxin A--identifying human antibodies and Fab fragments with favorable characteristics for antibody-drug conjugate development.

Antibody-drug conjugates (ADC) represent promising agents for targeted cancer therapy. To allow rational selection of human antibodies with favorable characteristics for ADC development a screening tool was designed obviating the need of preparing individual covalently linked conjugates. Therefore, α-kappa-ETA' was designed as a fusion protein consisting of a human kappa light chain binding antibody fragment and a truncated version of Pseudomonas exotoxin A. α-kappa-ETA' specifically bound to human kappa light chains of human or human-mouse chimeric antibodies and Fab fragments. Antibody-redirected α-kappa-ETA' specifically inhibited proliferation of antigen-expressing cell lines at low toxin and antibody concentrations. Selected antibodies that efficiently delivered α-kappa-ETA' in the novel assay system were used to generate scFv-based covalently linked immunotoxins. These molecules efficiently triggered apoptosis of target cells, indicating that antibodies identified in our assay system can be converted to functional immunoconjugates. Finally, a panel of human epidermal growth factor receptor (EGFR) antibodies was screened--demonstrating favorable characteristics with antibody 2F8. These data suggest that antibodies with potential for Pseudomonas exotoxin A-based ADC development can be identified using the novel α-kappa-ETA' conjugate.

Expression of CD64 (FcγRI) in skin of patients with acute GVHD.

GVHD remains a major problem in allo-SCT. We explored the presence of APC in skin biopsies of GVHD patients, using the IgG receptor CD64 expression as a hallmark for activated APC. By immunohistochemistry we demonstrated CD64 to be upregulated on host APC in skin biopsies of patients with acute GVHD and, less prominently, in chronic GVHD. Double staining for CD32 polymorphism revealed CD64-positive cells to be mainly of host origin. The majority of CD64-positive cells coexpressed CD68, indicating a macrophage phenotype. Given its very restricted cellular distribution, CD64 may represent an excellent target for APC-directed therapies in GVHD.

Treatment of rheumatoid arthritis patients with anti-TNF-alpha monoclonal antibody is accompanied by down-regulation of the activating Fcgamma receptor I on monocytes.

OBJECTIVES: To study the effect of anti-TNF-alpha therapy on activating IgG Fc receptor (FcgammaR) expression on monocytes of RA patients in relation to changes in disease activity. METHODS: RA patients were treated with anti-TNF-alpha mAb (infliximab). At baseline, 2 and 14 weeks after the start of anti-TNF-alpha treatment, FcgammaR expression levels on circulating monocytes were evaluated. Changes in expression were correlated to changes in disease parameters. To study the direct effects of TNF-alpha blockade on monocytic FcgammaR expression levels, monocytes were isolated and cultured with anti-TNF-alpha mAb. The effects were compared with those induced by TNF-alpha. RESULTS: Two weeks after the start of anti-TNF-alpha mAb therapy, monocytic FcgammaRI expression levels were decreased, whereas FcgammaRIIa and IIIa expression levels were unchanged. At 14 weeks, 8 weeks after the last gift of anti-TNF-alpha mAb, FcgammaRI expression levels returned to baseline levels. FcgammaRIIa and IIIa expression levels remained unchanged. The change in FcgammaRI correlated with changes in CRP and ESR levels. In vitro, anti-TNF-alpha mAb treatment did not alter expression of FcgammaRI on monocytes, but increased FcgammaRIIa and IIIa. TNF-alpha down-regulated all activating FcgammaRs, mainly FcgammaRIIa and IIIa, but also the inhibitory FcgammaRIIb. CONCLUSION: Anti-TNF-alpha mAb treatment of RA patients is accompanied by down-regulation of FcgammaRI expression levels on monocytes. This is likely an indirect effect of TNF-alpha blockade on disease activity, since in vitro anti-TNF-alpha mAb does not directly change FcgammaRI expression on monocytes. In contrast, TNF-alpha down-regulated all activating FcgammaRs. Thus, blocking TNF-alpha may relieve the negative feedback mechanism of TNF-alpha as down-regulator of FcgammaRs. Strategies to reduce activating FcgammaRs may have additional value in the treatment of RA patients with TNF-alpha blockade by diminishing immune complex-mediated activation of monocytes/macrophages.

In situ depletion of CD4+ T cells in human skin by Zanolimumab.

CD4(+) T cells, in activated or malignant form, are involved in a number of diseases including inflammatory skin diseases such as psoriasis, and T cell lymphomas such as the majority of cutaneous T cell lymphomas (CTCL). Targeting CD4 with an antibody that inhibits and/or eliminates disease-driving T cells in situ may therefore be a useful approach in the treatment of inflammatory and malignant skin diseases. Depletion of CD4(+) T cells in intact inflamed human skin tissue by Zanolimumab, a fully human therapeutic monoclonal antibody (IgG1, kappa) against CD4, was studied in a human psoriasis xenograft mouse model. Zanolimumab treatment was shown to induce a significant reduction in the numbers of inflammatory mononuclear cells in upper dermis. This reduction in inflammatory mononuclear cells in situ was primarily due to a significant reduction in the numbers of skin-infiltrating CD4(+), but not CD8(+) CD3(+) T cells. The capacity of Zanolimumab to deplete the CD4(+) T cells in the skin may be of importance in diseases where CD4(+) T cells play a central role. Indeed, in a phase II clinical trial Zanolimumab has shown a dose-dependent clinical response in patients with CTCL and the antibody is currently in a phase III clinical trial for CTCL, a disease for which there is no safe and effective treatment available today.

Fcgamma receptor polymorphisms and periodontal status: a prospective follow-up study.

AIMS: The aims of this study were to assess: (i) the distribution of Fcgamma receptor polymorphisms among patients with chronic periodontitis ("cases") and control subjects with no/minimal loss of periodontal tissue support in a Caucasian population; (ii) whether these polymorphisms can serve as severity markers for periodontitis; and (iii) whether they have any bearing on the response to periodontal therapy. METHODS: The study sample consisted of 132 cases and 73 controls of comparable age and gender. Full-mouth periodontal status was assessed. Subgingival plaque (PL) samples and blood samples were obtained and analysed with respect to 19 bacterial species and homologous serum immunoglobulin G titres. Polymorphisms in the Fcgamma receptor IIa (131R/H) and IIIb (NA1/NA2) were assessed by polymerase chain reaction. Patients underwent periodontal therapy and were followed up at 4 and 30 months. RESULTS: Neither polymorphism showed a skewed distribution among cases and controls. At baseline, periodontitis patients with Fcgamma RIIa-H/H131 genotype had more PL and deeper pockets than patients in other genotype groups (p < 0.05). Both bacterial levels and antibody titres were unrelated to genotype. The longitudinal analysis failed to detect an association between genotype and response to periodontal therapy. CONCLUSIONS: The present data failed to demonstrate a clinically relevant relationship between the Fcgamma receptor IIa (131R/H) or IIIb (NA1/NA2) polymorphism and periodontal status.

Down-regulation of activating Fcgamma receptors on monocytes of patients with rheumatoid arthritis upon methotrexate treatment.

OBJECTIVE: To determine the effect of methotrexate (MTX) on expression levels of activating receptors for IgG (FcgammaRs) on monocytes of rheumatoid arthritis (RA) patients in relation to changes in disease activity. METHODS: The effect of MTX on FcgammaRs on monocytes of RA patients was evaluated ex vivo as well as in vitro. Recently diagnosed, disease-modifying antirheumatic drug (DMARD)-naive RA patients were treated with low-dose MTX. At baseline and 16 weeks after the start of MTX treatment, changes in FcgammaR expression levels on peripheral blood monocytes were evaluated by fluorescence-activated cell sorting analysis and were correlated to changes in disease parameters. To study the direct effects of MTX on monocytes, these cells were isolated from peripheral blood monocytes of healthy controls and cultured with MTX. Other monocyte surface molecules (CD40, CD80, CD86, MHC class II) were also determined to test the specificity of the effect on FcgammaR expression levels. RESULTS: Eleven out of 15 patients improved clinically (mean disease activity score before 6.2 +/- 0.8 vs 4.3 +/- 1.7 after). Sixteen weeks after the start of MTX therapy, the expression levels of FcgammaRI and IIa on monocytes were significantly decreased, whereas the decreases in FcgammaRIIIa expression levels on monocytes were less marked. The percentage decrease in FcgammaRI expression correlated with the percentage decrease in CRP and well-being. In vitro MTX selectively decreased FcgammaRI and FcgammaRIIa expression levels of isolated monocytes, in contrast to other surface molecules. CONCLUSION: The disease-modifying effect of MTX in the treatment of RA is accompanied by down-regulation of activating FcgammaRI and IIa on monocytes, which could be a direct effect of MTX on monocytes. This down-regulation represents a new mode of action of MTX which should be considered in RA patients, especially during conditions that could give rise to monocyte activation by IgG-containing immune complexes, e.g. during antibody-based therapy of RA.

Depletion of synovial macrophages in rheumatoid arthritis by an anti-FcgammaRI-calicheamicin immunoconjugate.

BACKGROUND: Monocytes/macrophages have an important and versatile role in joint inflammation and destruction in rheumatoid arthritis (RA). OBJECTIVE: To determine the efficiency of monocyte/macrophage elimination by a new drug conjugated antibody (CD64-calicheamicin (CD64-CaMi)) directed to the high affinity receptor for IgG (FcgammaRI). METHODS: Mononuclear cells from peripheral blood and synovial fluid of patients with RA were cultured in the presence of CD64-CaMi. Cell death of monocytes/macrophages was measured by analysis of phenotypic changes (light scatter patterns, CD14 expression, and FcgammaRI expression) and nuclear DNA fragmentation. The selectivity of CD64-CaMi was checked by using FcgammaRI deficient and FcgammaRI transfected cell lines. In addition, the indirect effect of CD64-CaMi-induced macrophage cell death on arthritogenic T(h1) cell activity was determined. RESULTS: Inflammatory macrophages from RA synovial fluid, expressing increased FcgammaRI levels, were efficiently killed by CD64-CaMi through induction of DNA fragmentation. CD64-CaMi-induced cell death of monocytes/macrophages from peripheral blood of patients with RA proved less efficient. Induction of synovial macrophage death by CD64-CaMi was accompanied by efficient inhibition of proinflammatory T(h1) cytokine production. CONCLUSION: Together, the presented data suggest that elimination of macrophages through a new FcgammaRI directed CD64-CaMi is feasible. Because monocytes from peripheral blood are also eliminated by this immunoconjugate, additional experimental studies should validate its potential for local (intra-articular) application in the treatment of RA.

A novel polymorphism of FcalphaRI (CD89) associated with aggressive periodontitis.

Immunoglobulin A Fc receptor (FcalphaRI) has been implicated in the pathogenesis of periodontitis, because increased IgA responses and FcalphaRI-bearing neutrophils are observed in the disease lesions. Inter-individual differences in susceptibility to periodontitis may be attributable to genetic variability in FcalphaRI-mediated immunity. We here identified an FcalphaRI novel polymorphism (nt 324 A-to-G transition) in the membrane-distal extracellular domain encompassing the ligand-binding site, not resulting in an amino acid change. We compared the FcalphaRI genotype distributions among 46 Japanese aggressive periodontitis (AGP) patients, 80 race-matched healthy controls (HCs), and 59 Caucasian HCs. No ethnic differences were observed in the FcalphaRI genotype distributions between Japanese and Caucasian HC. Notably, we observed a difference in the genotype distribution between the AGP and HC groups. Carriage rate of the nt 324 A allele was higher in the AGP (65.2%) than that in the HC group (42.5%) (odds ratio 2.54). Polymorphonuclear neutrophils from peripheral blood and gingival crevicular fluid exhibited a decreased phagocytosis of periodontopathic bacteria (Porphyromonas gingivalis) in the nt 324 A/A patients as compared with the nt 324 G/G patients. These results document a genetic polymorphism at the FcalphaRI ligand-binding site to be associated with susceptibility to AGP.

Phase I clinical trial of the bispecific antibody MDX-H210 (anti-FcgammaRI x anti-HER-2/neu) in combination with Filgrastim (G-CSF) for treatment of advanced breast cancer.

A phase I study of the bispecific antibody MDX-H210 in combination with granulocyte colony-stimulating factor (G-CSF) was performed in stage IV breast carcinoma patients, overexpressing HER-2/neu. MDX-H210, constructed by crosslinking antigen binding fragments (F(ab') fragments) of monoclonal antibody (mAb) H22 to Fc gamma receptor I (FcgammaRI), and mAb 520C9 to HER-2/neu, respectively, mediates the lysis of tumour cells in vitro, and in human FcgammaRI transgenic mouse models. The proto-oncogene HER-2/neu is overexpressed in approximately 30% of breast cancer patients, and represents a promising target for antibody-based immunotherapy. Fc gamma receptor I (CD64) is an effective trigger molecule, which is expressed on monocytes/macrophages, immature dendritic cells, and G-CSF-primed polymorphonuclear cells (PMN). Patients received G-CSF (Filgrastim) for 8 consecutive days, and cohorts of three patients were treated on day 4 with escalating, single doses of MDX-H210. A total of 30 patients were included, and treatment was generally well tolerated, without reaching dose-limiting toxicity. Side effects consisted mainly of fever and short periods of chills, which were timely related to elevated plasma levels of interleukin 6 and tumour necrosis factor alpha. In the last two cohorts, MDX-H210 plasma levels exceeded 1 microg ml(-1), and on circulating myeloid cells >50% saturation of FcgammaRI was found until day 4. These effector cells were highly effective in antibody-dependent cell-mediated cytotoxicity. Immunohistochemical analyses of tumour biopsies in individual patients documented infiltration of monocytes and PMN after MDX-H210 infusion. Although the clinical course of the disease was not altered by the single dose of MDX-H210, a favourable toxicity profile--even at high doses--and remarkable biological effects were seen when combined with G-CSF. Therefore, the combination of G-CSF and MDX-H210 should be evaluated in further immunotherapeutical strategies.

Association of the Fc gamma receptor IIA-R/R131 genotype with myasthenia gravis in Dutch patients.

Myasthenia gravis (MG) susceptibility is partially determined by allelic heterogeneity of immune-modulatory genes. IgG receptors (FcgammaR) link the humoral and cellular branches of the immune system, and regulate immune responses and inflammation. Three FcgammaR subclasses (FcgammaRIIa, FcgammaRIIIa, and FcgammaRIIIb) exhibit functional polymorphisms, which affect efficiency of FcgammaR-mediated functions. FcgammaRIIa genotypes, but not FcgammaRIIIa and FcgammaRIIIb genotypes, were differentially distributed among 107 MG patients as compared to 239 healthy controls (Pz.Lt;0.01), with a relative increase of the FcgammaRIIa-R/R131 genotype (Odds ratio 2.4, 95% confidence interval 1.4-3.9). These data suggest that the FcgammaRIIa-R/R131 genotype is a marker for susceptibility to MG.

Fcgamma receptor polymorphisms in relation to periodontitis.

OBJECTIVES: Evidence suggests functional relevance for polymorphisms in FcgammaR in relation to inflammatory and infectious diseases. The present aim was to investigate genetic polymorphisms in three FcgammaR in relation to susceptibility and severity of periodontitis. MATERIAL AND METHODS: The study population consisted of 68 periodontitis patients and 61 controls (Northern European Caucasian background, mean ages 44 and 42 years, respectively). Among the patients, 12 subjects were diagnosed with aggressive periodontitis (AgP) and 56 individuals were diagnosed with chronic periodontitis (CP). Radiographic bone levels were scored for all teeth in the patients. Subjects were typed for the following genes (alleles): FcgammaRIIa (R131 or H131), FcgammaRIIIa (V158 or F158) and FcgammaRIIIb (NA1 or NA2). RESULTS: Hardy-Weinberg equilibrium criteria were fulfilled for the different genotypes at the three genes investigated. The frequency of the FcgammaRIIIa-V158 allele in the patient population (53%) was higher than in the control group (39%) (OR 1.73 [1.06-2.85], p=0.034). The V158 carriage rate in AgP was even higher (63%). The frequency of the FcgammaRIIa-H131 allele in the total periodontitis population was 58%; for AgP this was 79%, compared with 51% in the control population (OR 3.68 [1.29-10.5], p=0.013). Also, the frequency of the FcgammaRIIa-H/H131 genotype was significantly higher in AgP patients than in controls (OR 9.07 [1.29-63.56], p=0.026, adjusted for smoking status and other potential confounders). Moreover, patients with the FcgammaRIIa-H/H131 genotype had more severe radiographic bone loss than patients with the other FcgammaRIIa genotypes. CONCLUSION: The current study of relative small sample size suggests that the FcgammaRIIa-H/H131 genotype may be a putative susceptibility and severity factor, and the FcgammaRIIIa-V158 allele a putative susceptibility factor for periodontitis in Northern European Caucasians. These results need further verification and the biological importance of these findings needs further investigation.

FcgammaR polymorphisms: Implications for function, disease susceptibility and immunotherapy.

Leukocyte Fcgamma receptors (FcgammaR) confer potent cellular effector functions to the specificity of IgG. FcgammaR-induced leukocyte functions, including antibody-dependent cellular cytotoxicity, phagocytosis, superoxide generation, degranulation, cytokine production and regulation of antibody production, are essential for host defense and immune regulation. The efficacy of IgG-induced FcgammaR function displays inter-individual heterogeneity due to genetic polymorphisms of three FcgammaR subclasses, FcgammaRIIa (CD32a), FcgammaRIIIa (CD16a), and FcgammaRIIIb (CD16b). FcgammaR polymorphisms have been associated with infectious and autoimmune disease, or with disease severity. FcgammaR polymorphisms may furthermore serve as markers for therapeutic efficacy and side-effects of treatment with monoclonal antibodies. In this review, FcgammaR function and the relevance of FcgammaR polymorphisms as prognostic markers for inflammatory disease and antibody-based immunotherapy are discussed.

Fcgamma receptor expression levels on monocytes are elevated in rheumatoid arthritis patients with high erythrocyte sedimentation rate who do not use anti-rheumatic drugs.

OBJECTIVES: Levels of immunoglobulin G (IgG) Fc receptors (FcgammaRs) affect the activity and function of monocytes/macrophages when binding IgG-containing immune complexes. Hence, the expression level of FcgammaRs on monocytic cells may influence inflammation in patients with rheumatoid arthritis (RA). In this study the expression levels of FcgammaRI, IIa and IIIa on peripheral blood monocytes of RA patients were compared with those of healthy controls and related to patient and disease characteristics and the use of disease-modifying anti-rheumatic drugs (DMARDs). In addition, FcgammaR expression levels were determined on RA synovial fluid macrophages and compared with those in RA peripheral blood. METHODS: Mononuclear cells from peripheral blood and synovial fluid were isolated and FcgammaR expression levels on CD14-positive cells were analysed by flow cytometry. The effects of patient and disease characteristics and the use of DMARDs were assessed. RESULTS: A high expression level of FcgammaRIIa and high percentages of FcgammaRIIIa-expressing monocytes were found in RA patients with a high erythrocyte sedimentation rate. DMARD-naive early RA patients had higher FcgammaRIIa expression levels but a similar amount of FcgammaRIIIa-positive monocytes compared with RA patients using DMARDs. In synovial fluid, FcgammaRIIa expression levels were lower than in RA peripheral blood, whereas the percentage of FcgammaRIIIa-positive monocytic cells was higher in synovial fluid than in peripheral blood. CONCLUSIONS: These data point to the involvement of FcgammaRs, specifically FcgammaRIIa and IIIa, in the immune response of RA and suggest that FcgammaR expression levels are susceptible to modulation by DMARD therapy.

Clearance of red cells by monoclonal IgG3 anti-D in vivo is affected by the VF polymorphism of Fcgamma RIIIa (CD16).

Human red cells (RBC) coated with IgG anti-D are cleared from the circulation to the spleen by macrophages which express IgG receptors (Fcgamma R). Polymorphisms of Fcgamma RIIa and Fcgamma RIIIa affect IgG binding in vitro, and may alter the efficiency of clearance of immune complexes in vivo. In a RBC clearance study, 22 Rh D-negative subjects were given 100-400 micro g human monoclonal or polyclonal IgG anti-D i.m. followed 48 h later by 51Cr-labelled D+ RBC. The half lives of the infused D+ RBC were determined, together with the coating levels of anti-D on the D+ RBC. Fcgamma RIIA and FcgammaRIIIA genotyping was performed. Large ranges of phagocytosis and extracellular lysis of RBC in vitro, and of half lives of RBC in vivo, were observed. Clearance of RBC coated with monoclonal IgG3 anti-D (BRAD-3) was more rapid in five subjects homozygous for Fcgamma RIIIa-F/F158 than in three subjects expressing the Fcgamma RIIIa-V158 allele (P = 0.024). This effect was not observed, however, for those individuals given polyclonal anti-D. There was also no significant difference in the efficiency of RBC destruction in vitro or of RBC clearance in vivo between the subjects analysed for individual genotypes or alleles or combinations of alleles. In conclusion, the presence of the Fcgamma RIIIa-V158 allele compromised the efficiency of removal of RBC coated with IgG3 anti-D.

Fcgamma receptor IIa, IIIa, and IIIb polymorphisms in German patients with systemic lupus erythematosus: association with clinical symptoms.

BACKGROUND: Receptors for IgG play an important part in immune complex clearance. Several studies have identified polymorphisms of receptors for the Fc fragment of IgG (FcgammaR) as genetic factors influencing susceptibility to disease or disease course of systemic lupus erythematosus (SLE). OBJECTIVE: To examine these possibilities by evaluating a panel of clinical parameters in a cohort of 140 German patients with SLE for correlations with the FcgammaRIIa, IIIa, and IIIb polymorphisms in an explorative study. METHODS: 140 German patients with SLE according to American College of Rheumatology (ACR) criteria and 187 German controls were genotyped for the FcgammaRIIa, IIIa, and IIIb polymorphisms. Associations between FcgammaR genotypes, combined genotypes and clinical as well as laboratory features were analysed. RESULTS: No significant skewing of any of the three FcgammaR polymorphisms was seen in the German SLE cohort studied. Various clinical and serological parameters were found more frequently and at younger age in homozygous patients with the genotypes IIA-R/R131 or IIIA-F/F158 than in patients with IIA-H/H131 or IIIA-V/V158. These effects were even more pronounced in patients with the low binding combined phenotypes of the FcgammaRIIa, IIIa (double negative phenotypes) and FcgammaRIIa, IIIa, and IIIb (triple negative phenotypes). In patients with the double negative IIA and IIIA genotypes significantly higher frequencies of nephritis (63% v 33%) and proteinuria according to ACR criteria (58% v 11%), anaemia (84% v 55%), and anticardiolipin antibodies (63% v 22%) were found than in patients with the double positive genotypes. Patients with the IIA-R/R131 genotype and the double negative homozygous genotype had an earlier incidence of clinical symptoms, haematological and immunological abnormalities. Accordingly, SLE is diagnosed earlier in these patients, the difference reaching statistical significance only in the double negative v the double positive genotype (26.3 v 39.5 years) and the IIIA-F/F158 genotype v the rest (26.7 v 32.0 years). Most relevant is the fact that a higher median disease activity (ECLAM score) was demonstrated, both in the IIA-R/R131 homozygous (3.3 v 2.7) and the double negative (3.4 v 2.3) patients, reaching statistical significance in the first group. CONCLUSION: The results of this explorative study support the view that the FcgammaRIIa/IIIa and IIIb polymorphisms constitute factors influencing clinical manifestations and the disease course of SLE but do not represent genetic risk factors for the occurrence of SLE. Higher frequencies of clinical symptoms, haematological and immunological abnormalities as well as an earlier onset of clinical symptoms, haematological and immunological markers of active disease were found in patients with the IIA-R/R131 genotype and the double negative and triple negative genotypes.

FcgammaRI (CD64) contributes substantially to severity of arthritis, hypersensitivity responses, and protection from bacterial infection.

The high-affinity receptor for IgG, FcgammaRI, shares its capacity to bind IgG2a immune complexes (IgG2a-IC) with the low-affinity receptor FcgammaRIII and complement factors, hampering the definition of its biological role. Moreover, in vivo, FcgammaRI is occupied by monomeric IgG2a, reducing its accessibility to newly formed IgG2a-IC. By using a variety of FcgammaR(-/-) mice, we demonstrate that in the absence of FcgammaRI, the IgG2a-IC-induced cellular processes of phagocytosis, cytokine release, cellular cytotoxicity, and antigen presentation are impaired. FcgammaRI(-/-) mice showed impaired hypersensitivity responses, strongly reduced cartilage destruction in an arthritis model, and impaired protection from a bacterial infection. We conclude that FcgammaRI contributes substantially to a variety of IgG2a-IC-dependent immune functions and immunopathological responses.

Epidermal growth factor receptor and g250: useful target antigens for antibody mediated cellular cytotoxicity against renal cell carcinoma?

PURPOSE: Monoclonal antibodies are a novel treatment option for certain tumor patients. We evaluated the potential of antibody derivatives against epidermal growth factor receptor and G250, which are 2 candidate antigens on renal cell carcinoma, to recruit effector cells for killing renal cell carcinoma. MATERIAL AND METHODS: As a measure of cytotoxicity, 51chromium release assays against renal cell carcinoma lines were performed using unseparated blood or isolated cell populations as the source of effectors. Blood was obtained from healthy donors, or from patients receiving granulocyte-macrophage colony-stimulating factor or granulocyte colony-stimulating factor for enhancing effector cell function. Parental human IgG1 antibodies against epidermal growth factor receptor and G250 were compared with respective chemically linked bispecific antibodies targeting IgA Fc receptor FcalphaRI (CD89), a novel cytotoxic trigger molecule on polymorphonuclear cells and monocytes/macrophages, which were constructed by chemically crosslinking appropriate F(ab') fragments. RESULTS: Renal cell carcinoma lines were highly resistant to complement dependent lysis. With mononuclear effector cells high levels of renal cell carcinoma killing were observed with a humanized epidermal growth factor receptor directed monoclonal antibody, while the same antibody did not recruit granulocytes (polymorphonuclear cells) for antibody dependent cell mediated cytotoxicity. However, polymorphonuclear cells effectively lysed renal cell carcinoma with [FcalphaRI x epidermal growth factor receptor] bispecific antibody. FcalphaRI mediated killing was significantly enhanced when the blood of patients on granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor therapy was analyzed. However, G250 mediated only low levels of killing with mononuclear cell but not with polymorphonuclear effector cells. CONCLUSIONS: Targeting epidermal growth factor receptor proved to recruit efficiently mononuclear or polymorphonuclear cell mediated killing mechanisms, while G250 directed antibody constructs were significantly less effective. Particularly effective renal cell carcinoma killing was observed with combined [FcalphaRI x epidermal growth factor receptor] bispecific antibody and granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor.