IgG Fc receptor polymorphisms in human disease: implications for intravenous immunoglobulin therapy

Intravenous immunoglobulin alleviates Japanese encephalitis virus-induced peripheral neuropathy by inhibiting the ASM/ceramide pathway

Japanese encephalitis virus (JEV) infection is considered a global public health emergency. Severe peripheral neuropathy caused by JEV infection has increased disability and mortality rates in recent years. Because there are very few therapeutic options for JEV infection, prompt investigations of the ability of clinically safe, efficacious and globally available drugs to inhibit JEV infection and ameliorate peripheral neuropathy are urgently needed. In this study, we found that high doses of intravenous immunoglobulin, a function inhibitor of acid sphingomyelinase (FIASMA), inhibited acid sphingomyelinase (ASM) and ceramide activity in the serum and sciatic nerve of JEV-infected rats, reduced disease severity, reversed electrophysiological and histological abnormalities, significantly reduced circulating proinflammatory cytokine levels, inhibited Th1 and Th17 cell proliferation, and suppressed the infiltration of inflammatory CD4 + cells into the sciatic nerve. It also maintained the peripheral nerve-blood barrier without causing severe clinical side effects. In terms of the potential mechanisms, ASM was found to participate in immune cell differentiation and to activate immune cells, thereby exerting proinflammatory effects. Therefore, immunoglobulin is a FIASMA that reduces abnormal immune responses and thus targets the ASM/ceramide system to treat peripheral neuropathy caused by JEV infection.

A predictive nomogram for short-term outcomes of myasthenia gravis patients treated with low-dose rituximab

BACKGROUND

This study aims to establish and validate a predictive nomogram for the short-term clinical outcomes of myasthenia gravis (MG) patients treated with low-dose rituximab.

METHODS

We retrospectively reviewed 108 patients who received rituximab of 600 mg every 6 months in Huashan Hospital and Tangdu Hospital. Of them, 76 patients from Huashan Hospital were included in the derivation cohort to develop the predictive nomogram, which was externally validated using 32 patients from Tangdu Hospital. The clinical response is defined as a ≥ 3 points decrease in QMG score within 6 months. Both clinical and genetic characteristics were included to screen predictors via multivariate logistic regression. Discrimination and calibration were measured by the area under the receiver operating characteristic curve (AUC-ROC) and Hosmer-Lemeshow test, respectively.

RESULTS

Disease duration (OR = 0.987, p = 0.032), positive anti-muscle-specific tyrosine kinase antibodies (OR = 19.8, p = 0.007), and genotypes in FCGR2A rs1801274 (AG: OR = 0.131, p = 0.024;GG:OR = 0.037, p = 0.010) were independently associated with clinical response of post-rituximab patients. The nomogram identified MG patients with clinical response with an AUC-ROC (95% CI) of 0.875 (0.798-0.952) in the derivation cohort and 0.741(0.501-0.982) in the validation cohort. Hosmer-Lemeshow test showed a good calibration (derivation: Chi-square = 3.181, p = 0.923; validation: Chi-square = 8.098, p = 0.424).

CONCLUSIONS

The nomogram achieved an optimal prediction of short-term outcomes in patients treated with low-dose rituximab.

Pharmacogenomics of intravenous immunoglobulin response in Kawasaki disease

Introduction

Kawasaki disease (KD) is a diffuse vasculitis in children. Response to high dose intravenous gamma globulin (IVIG), the primary treatment, varies according to genetic background. We sought to identify genetic loci, which associate with treatment response using whole genome sequencing (WGS).

Method

We performed WGS in 472 KD patients with 305 IVIG responders and 167 non-responders defined by AHA clinical criteria. We conducted logistic regression models to test additive genetic effect in the entire cohort and in four subgroups defined by ancestry information markers (Whites, African Americans, Asians, and Hispanics). We performed functional mapping and annotation using FUMA to examine genetic variants that are potentially involved IVIG non-response. Further, we conducted SNP-set [Sequence] Kernel Association Test (SKAT) for all rare and common variants.

Results

Of the 43,288,336 SNPs (23,660,970 in intergenic regions, 16,764,594 in introns and 556,814 in the exons) identified, the top ten hits associated with IVIG non-response were in FANK1, MAP2K3:KCNJ12, CA10, FRG1DP, CWH43 regions. When analyzed separately in ancestry-based racial subgroups, SNPs in several novel genes were associated. A total of 23 possible causal genes were pinpointed by positional and chromatin mapping. SKAT analysis demonstrated association in the entire MANIA2, EDN1, SFMBT2, and PPP2R5E genes and segments of CSMD2, LINC01317, HIVEPI, HSP90AB1, and TTLL11 genes.

Conclusions

This WGS study identified multiple predominantly novel understudied genes associated with IVIG response. These data can serve to inform regarding pathogenesis of KD, as well as lay ground work for developing treatment response predictors.

Fc Receptor Variants and Disease: A Crucial Factor to Consider in the Antibody Therapeutics in Clinic

The fragment crystallizable (Fc) domain of antibodies is responsible for their protective function and long-lasting serum half-life via Fc-mediated effector function, transcytosis, and recycling through its interaction with Fc receptors (FcRs) expressed on various immune leukocytes, epithelial, and endothelial cells. Therefore, the Fc-FcRs interaction is a control point of both endogenous and therapeutic antibody function. There are a number of reported genetic variants of FcRs, which include polymorphisms in (i) extracellular domain of FcRs, which change their affinities to Fc domain of antibodies; (ii) both cytoplasmic and intracellular domain, which alters the extent of signal transduction; and (iii) the promoter region of the FcRs gene, which affects the expression level of FcRs, thus being associated with the pathogenesis of disease indications. In this review, we firstly describe the correlation between the genetic variants of FcRs and immunological disorders by individual differences in the extent of FcRs-mediated regulations. Secondly, we discuss the influence of the genetic variants of FcRs on the susceptibility to infectious diseases or cancer in the perspective of FcRs-induced effector functions. Overall, we concluded that the genetic variants of FcRs are one of the key elements in the design of antibody therapeutics due to their variety of clinical outcomes among individuals.

Influence of the FCGR2A rs1801274 and FCGR3A rs396991 Polymorphisms on Response to Abatacept in Patients with Rheumatoid Arthritis

Abatacept (ABA) is an immunosuppressant indicated for treatment of rheumatoid arthritis (RA). Effectiveness might be influenced by clinical RA variants and single-nucleotide polymorphisms (SNPs) in genes encoding protein FCGR2A (His131Arg) and FCGR3A (Phe158Val) involved in pharmacokinetics of ABA. An observational cohort study was conducted in 120 RA Caucasian patients treated with ABA for 6 and 12 months. Patients with the FCGR2A rs1801274-AA genotype (FCGR2A-p.131His) showed a better EULAR response (OR = 2.43; 95% CI = 1.01-5.92) at 12 months and low disease activity (LDA) at 6 months (OR = 3.16; 95% CI = 1.19-8.66) and 12 months (OR = 6.62; 95% CI = 1.25-46.89) of treatment with ABA. A tendency was observed towards an association between the FCGR3A rs396991-A allele (FCGR3A-p.158Phe) and better therapeutic response to ABA after 12 months of treatment (p = 0.078). Moreover, we found a significant association between the low-affinity FCGR2A/FCGR3A haplotypes variable and LDA after 12 months of ABA treatment (OR = 1.59; 95% CI = 1.01-2.58). The clinical variables associated with better response to ABA were lower age at starting ABA (OR = 1.06; 95% CI = 1.02-1.11) and greater duration of ABA treatment (OR = 1.02; 95% CI = 1.01-1.04), lower duration of previous biological therapies (OR = 0.99; 95% CI = 0.98-0.99), non-administration of concomitant disease-modifying antirheumatic drugs (DMARDs) (OR = 24.53; 95% CI = 3.46-523.80), non-use of concomitant glucocorticoids (OR = 0.12; 95% CI = 0.02-0.47), monotherapy (OR = 19.22; 95% CI = 2.05-343.00), lower initial patient's visual analogue scale (PVAS) value (OR = 0.95; 95% CI = 0.92-0.97), and lower baseline ESR (OR = 0.92; 95% CI = 0.87-0.97). This study showed that high-affinity FCGR2A-p.131His variant, low-affinity FCGR3A-p.158Phe variant, and combined use of FCGR2A/FCGR3A genetic variations could affect ABA effectiveness. Further studies will be required to confirm these results.

Fc-gamma IIIa-V158F receptor polymorphism contributes to the severity of Guillain-Barré syndrome

Objective

Guillain‐Barré syndrome (GBS) is a rare, life‐threatening disorder of the peripheral nervous system. Immunoglobulin G Fc‐gamma receptors (FcγRs) mediate and regulate diverse effector functions and are involved in the pathogenesis of GBS. We investigated whether the FcγR polymorphisms FcγRIIa H/R131 (rs1801274), FcγRIIIa V/F158 (rs396991), and FcγRIIIb NA1/NA2, and their haplotype patterns affect the affinity of IgG‐FcγR interactivity and influence GBS susceptibility and severity.

Methods

We determined FcγR polymorphisms in 303 patients with GBS and 302 ethnically matched healthy individuals from Bangladesh by allele‐specific polymerase chain reaction. Pairwise linkage disequilibrium and haplotype patterns were analyzed based on D ´statistics and the genotype package of R statistics, respectively. Logistic regression analysis and Fisher’s exact test with corrected P (Pc) values were employed for statistical comparisons.

Results

FcγRIIIa‐V158F was associated with the severe form of GBS compared to the mild form (P = 0.005, OR = 2.24, 95% CI = 1.28–3.91; Pc = 0.015); however, FcγR genotypes and haplotype patterns did not show any association with GBS susceptibility compared to healthy controls. FcγRIIIa‐V/V158 and FcγRIIIb‐NA2/2 were associated with recent Campylobacter jejuni infection (P ≤ 0.001, OR = 0.36, 95% CI = 0.23–0.56; Pc ≤ 0.003 and P = 0.004, OR = 1.70, 95% CI = 1.18–2.44; Pc ≤ 0.012, respectively). Haplotype 1 (FcγRIIa‐H131R‐ FcγRIIIa‐V158F‐ FcγRIIIb‐NA1/2) and the FcγRIIIb‐NA2/2 genotype were more prevalent among anti‐GM1 antibody‐positive patients (P = 0.031, OR = 9.61, 95% CI = 1.24–74.77, Pc = 0.279; P = 0.027, OR = 1.62, 95% CI = 1.06–2.5, Pc = 0.081, respectively).

Interpretation

FcγR polymorphisms and haplotypes are not associated with susceptibility to GBS, though the FcγRIIIa‐V158F genotype is associated with the severity of GBS.

Association between polymorphisms in EGFR and tumor response during cetuximab and oxaliplatin-based combination therapy in metastatic colorectal cancer: Analysis of data from two clinical trials

Predicting tumor response prior to starting anti-epidermal growth factor receptor (EGFR) antibody therapy would benefit patients with advanced/metastatic colorectal cancer (mCRC). The present study investigated the association between efficacy of cetuximab treatment and gene polymorphisms of fragment C γ receptor (FcγR) 2A, FcγR3A and EGFR in patients with extended RAS/BRAF wild-type mCRC. Clinical data and specimens were obtained from 90 patients who participated in either of two clinical studies evaluating the first-line, cetuximab plus oxaliplatin-based treatment. It was hypothesized that polymorphisms H/H of FcγR2A, V/V of FcγR3A, K/K of EGFR and <36 CA repeats in the EGFR gene may be associated with a favorable tumor response. Multivariate analysis demonstrated that patients with the H/H polymorphism tended to have an improved tumor response compared with the non-H/H population, although the result was not significant [odds ratio, 2.25; 95% confidence interval (CI), 0.89–5.66; P=0.09]. Univariate analysis revealed increased tumor shrinkage in patients with the K/K polymorphism of EGFR compared with the other polymorphisms (mean ± standard deviation, −55.3±28.4 vs. −39.6±40.8%; P=0.04). Subsequent multivariate analysis confirmed that the K/K polymorphism of EGFR predicted greater tumor shrinkage (multiple linear regression analysis estimate, −19.3; 95% CI, −35.5 to 3.0; P=0.02), with the tendency toward a preferable response in patients with <36 CA EGFR gene repeats (estimate, −16.9; 95% CI; −34.4 to 0.6; P=0.06). However, other polymorphisms and clinical variables did not predict tumor shrinkage. In conclusion, the present study demonstrated that polymorphisms of EGFR, FcγR2A and FcγR3A may differentiate the patients that obtain the maximum benefit from cetuximab treatment.

SLE-associated risk factors affect DC function

Numerous risk alleles for systemic lupus erythematosus (SLE) have now been identified. Analysis of the expression of genes with risk alleles in cells of hematopoietic origin demonstrates them to be most abundantly expressed in B cells and dendritic cells (DCs), suggesting that these cell types may be the drivers of the inflammatory changes seen in SLE. DCs are of particular interest as they act to connect the innate and the adaptive immune response. Thus, DCs can transform inflammation into autoimmunity, and autoantibodies are the hallmark of SLE. In this review, we focus on mechanisms of tolerance that maintain DCs in a non‐activated, non‐immunogenic state. We demonstrate, using examples from our own studies, how alterations in DC function stemming from either DC‐intrinsic abnormalities or DC‐extrinsic regulators of function can predispose to autoimmunity.

FcGR genetic polymorphisms and the response to adalimumab in patients with rheumatoid arthritis

AIM

The aim of our study was to explore the potential of FcGR genetic polymorphisms as a predictor of adalimumab efficacy in rheumatoid arthritis (RA) patients.

MATERIALS & METHODS

The study population was composed of 302 Dutch RA patients receiving adalimumab therapy. The FcGR2A (R131>H; rs1801274) and FcGR3A (F158>V; rs396991) genetic variants were genotyped using the TaqMan(®) allelic discrimination technology. Treatment outcome was evaluated with the use of the 28-joint disease activity score criteria (DAS28) and good response and remission were classified according to European League Against Rheumatism (EULAR) criteria.

RESULTS

Comparing allelic frequencies between responders and nonresponders, the presence of the FcGR2A*R allele was associated with EULAR good response at 14 weeks (p = 0.017, odds ratio: 1.53, 95% CI: 1.08-2.17). No significant association was found for FcGR3A, with good response or remission. The combined effect of both FcGR2A and FcGR3A SNPs showed a trend for association with EULAR good response (p-value = 0.041, odds ratio: 1.38, 95% CI: 1.01-1.89).

CONCLUSION

Our results indicate that FcGR polymorphisms could be a determinant of adalimumab efficacy in RA patients. Original submitted 28 July 2014; Revision submitted 19 December 2014.

The Role of FcRn in Antigen Presentation

Immunoglobulins are unique molecules capable of simultaneously recognizing a diverse array of antigens and themselves being recognized by a broad array of receptors. The abundance specifically of the IgG subclass and the variety of signaling receptors to which it binds render this an important immunomodulatory molecule. In addition to the classical Fcγ receptors that bind IgG at the cell surface, the neonatal Fc receptor (FcRn) is a lifelong resident of the endolysosomal system of most hematopoietic cells where it determines the intracellular fate of both IgG and IgG-containing immune complexes (IgG IC). Cross-linking of FcRn by multivalent IgG IC within antigen presenting cells such as dendritic cells initiates specific mechanisms that result in trafficking of the antigen-bearing IgG IC into compartments from which the antigen can successfully be processed into peptide epitopes compatible with loading onto both major histocompatibility complex class I and II molecules. In turn, this enables the synchronous activation of both CD4⁺ and CD8⁺ T cell responses against the cognate antigen, thereby bridging the gap between the humoral and cellular branches of the adaptive immune response. Critically, FcRn-driven T cell priming is efficient at very low doses of antigen due to the exquisite sensitivity of the IgG-mediated antigen delivery system through which it operates. FcRn-mediated antigen presentation has important consequences in tissue compartments replete with IgG and serves not only to determine homeostatic immune activation at a variety of sites but also to induce inflammatory responses upon exposure to antigens perceived as foreign. Therapeutically targeting the pathway by which FcRn enables T cell activation in response to IgG IC is thus a highly attractive prospect not only for the treatment of diseases that are driven by immune complexes but also for manipulating local immune responses against defined antigens such as those present during infections and cancer.

PRTX-100 and methotrexate in patients with active rheumatoid arthritis: A Phase Ib randomized, double-blind, placebo-controlled, dose-escalation study

PRTX-100 is a highly-purified preparation of staphylococcal protein A (SpA), with immunologic activity in vitro and in animal models of immune-mediated inflammation. Following single-dose healthy volunteer studies of safety and pharmacokinetics (PK), a multicenter, double-blind, placebo-controlled, sequential dose-escalation, repeated-dose phase I trial was conducted in patients with active rheumatoid arthritis (RA) on methotrexate therapy. Patients were randomized to receive either weekly intravenous PRTX-100 (0.15, 0.45, 0.90, or 1.50 µg/kg) or placebo for 4 weeks. Safety and disease activity were assessed over 16 weeks. Pharmacokinetic profiles were obtained after the first and fourth doses. The most common treatment-related adverse events were nausea, muscle spasms, dizziness, flushing, fatigue, RA flare, and headache. No serious adverse events were considered related to PRTX-100, and none occurred in the highest dose group. Geometric mean values for plasma Cmax (ng/mL) were 4.1, 15.7, 26.5, and 51.2 for doses of 0.15, 0.45, 0.90, and 1.5 µg/kg, respectively. Anti-drug antibodies (ADAs) developed in most PRTX-100 patients, but incidence and titer were not dose-dependent. At the two highest doses, data suggest PRTX-100 may have an effect on RA disease activity, even in patients with ADAs.

Application of fluorescent monocytes for probing immune complexes on antigen microarrays

Microarrayed antigens are used for identifying serum antibodies with given specificities and for generating binding profiles. Antibodies bind to these arrayed antigens forming immune complexes and are conventionally identified by secondary labelled antibodies.In the body immune complexes are identified by bone marrow derived phagocytic cells, such as monocytes. In our work we were looking into the possibility of replacing secondary antibodies with monocytoid cells for the generation of antibody profiles. Using the human monocytoid cell line U937, which expresses cell surface receptors for immune complex components, we show that cell adhesion is completely dependent on the interaction of IgG heavy chains and Fcγ receptors, and this recognition is susceptible to differences between heavy chain structures and their glycosylation. We also report data on a possible application of this system in autoimmune diagnostics.Compared to secondary antibodies, fluorescent monocytesas biosensors are superior in reflecting biological functions of microarray-bound antibodies and represent an easy and robust alternative for profiling interactions between serum proteins and antigens.

Pharmacokinetics, pharmacodynamics and physiologically-based pharmacokinetic modelling of monoclonal antibodies

Development of monoclonal antibodies (mAbs) and their functional derivatives represents a growing segment of the development pipeline in the pharmaceutical industry. More than 25 mAbs and derivatives have been approved for a variety of therapeutic applications. In addition, around 500 mAbs and derivatives are currently in different stages of development. mAbs are considered to be large molecule therapeutics (in general, they are 2-3 orders of magnitude larger than small chemical molecule therapeutics), but they are not just big chemicals. These compounds demonstrate much more complex pharmacokinetic and pharmacodynamic behaviour than small molecules. Because of their large size and relatively poor membrane permeability and instability in the conditions of the gastrointestinal tract, parenteral administration is the most usual route of administration. The rate and extent of mAb distribution is very slow and depends on extravasation in tissue, distribution within the particular tissue, and degradation. Elimination primarily happens via catabolism to peptides and amino acids. Although not definitive, work has been published to define the human tissues mainly involved in the elimination of mAbs, and it seems that many cells throughout the body are involved. mAbs can be targeted against many soluble or membrane-bound targets, thus these compounds may act by a variety of mechanisms to achieve their pharmacological effect. mAbs targeting soluble antigen generally exhibit linear elimination, whereas those targeting membrane-bound antigen often exhibit non-linear elimination, mainly due to target-mediated drug disposition (TMDD). The high-affinity interaction of mAbs and their derivatives with the pharmacological target can often result in non-linear pharmacokinetics. Because of species differences (particularly due to differences in target affinity and abundance) in the pharmacokinetics and pharmacodynamics of mAbs, pharmacokinetic/pharmacodynamic modelling of mAbs has been used routinely to expedite the development of mAbs and their derivatives and has been utilized to help in the selection of appropriate dose regimens. Although modelling approaches have helped to explain variability in both pharmacokinetic and pharmacodynamic properties of these drugs, there is a clear need for more complex models to improve understanding of pharmacokinetic processes and pharmacodynamic interactions of mAbs with the immune system. There are different approaches applied to physiologically based pharmacokinetic (PBPK) modelling of mAbs and important differences between the models developed. Some key additional features that need to be accounted for in PBPK models of mAbs are neonatal Fc receptor (FcRn; an important salvage mechanism for antibodies) binding, TMDD and lymph flow. Several models have been described incorporating some or all of these features and the use of PBPK models are expected to expand over the next few years.

Rituximab in dermatology

Rituximab was introduced into clinical practice as a medication with considerable potential. Its use in patients with B-cell lymphoma and rheumatoid arthritis revealed numerous indications in autoimmune diseases, many of which involve the skin, thus requiring dermatologists to become familiar with both the characteristics of anti-CD20 antibodies and the role of B cells in multiple skin diseases. Thanks to these developments, we will be able to use rituximab more frequently and appropriately in our patients and draw up consensus guidelines based on large case series. In other words, establishing the indications for rituximab will make it possible to shorten disease course and reduce morbidity due to more specific drugs.

Prespecified candidate biomarkers identify follicular lymphoma patients who achieved longer progression-free survival with bortezomib-rituximab versus rituximab

PURPOSE

Identify subgroups of patients with relapsed/refractory follicular lymphoma deriving substantial progression-free survival (PFS) benefit with bortezomib-rituximab versus rituximab in the phase III LYM-3001 study.

EXPERIMENTAL DESIGN

A total of 676 patients were randomized to five 5-week cycles of bortezomib-rituximab or rituximab. The primary end point was PFS; this prespecified analysis of candidate protein biomarkers and genes was an exploratory objective. Archived tumor tissue and whole blood samples were collected at baseline. Immunohistochemistry and genetic analyses were completed for 4 proteins and 8 genes.

RESULTS

In initial pairwise analyses, using individual single-nucleotide polymorphism genotypes, one biomarker pair (PSMB1 P11A C/G heterozygote, low CD68 expression) was associated with a significant PFS benefit with bortezomib-rituximab versus rituximab, controlling for multiple comparison corrections. The pair was analyzed under dominant, recessive, and additive genetic models, with significant association with PFS seen under the dominant model (G/G+C/G). In patients carrying this biomarker pair [PSMB1 P11A G allele, low CD68 expression (≤50 CD68-positive cells), population frequency: 43.6%], median PFS was 14.2 months with bortezomib-rituximab versus 9.1 months with rituximab (HR 0.47, P < 0.0001), and there was a significant overall survival benefit (HR 0.49, P = 0.0461). Response rates were higher and time to next antilymphoma therapy was longer in the bortezomib-rituximab group. In biomarker-negative patients, no significant efficacy differences were seen between treatment groups. Similar proportions of patients had high-risk features in the biomarker-positive and biomarker-negative subsets.

CONCLUSIONS

Patients with PSMB1 P11A (G allele) and low CD68 expression seemed to have significantly longer PFS and greater clinical benefit with bortezomib-rituximab versus rituximab.

Fcγ receptor polymorphisms do not predict response to intravenous immunoglobulin in myasthenia gravis

We studied 63 patients with myasthenia gravis (MG) requiring treatment with intravenous immunoglobulin, to determine if polymorphisms within the FCγR2A (rs1801274), FCγR2B (rs1050501), FCγR3A (rs396991), and FCγR3B (NA1/NA2) genes are correlated with response to treatment. There was no significant difference in any of the polymorphisms studied between responders and nonresponders. Patients with the FCγR2B-232I/I polymorphism had higher disease severity measured by the quatitative myasthenia gravis score (QMGS). There was no difference in the distribution of the FCγR2B-232 polymorphisms between the patients and 90 healthy controls. The finding of greater disease severity in patients with the FCγR2B-232I/I polymorphism requires confirmation in a larger population of patients with myasthenia gravis.

Role of immunoglobulin G fragment C receptor polymorphism-mediated antibody-dependant cellular cytotoxicity in colorectal cancer treated with cetuximab therapy

Antibody-dependent cellular cytotoxicity (ADCC), which is activated by effector cells via immunoglobulin G (IgG) fragment C receptors (FcRs), was proposed as a mechanism of cetuximab efficacy. Peripheral blood mononuclear cells (PBMCs) from 23 healthy donors and 13 patients with metastatic colorectal cancer (mCRC) treated with cetuximab were tested for FcγR polymorphisms and cetuximab-mediated ADCC. ADCC was measured by chromium-51 release on a epidermal growth factor receptor (EGFR)-positive human colon cancer cell line. Overall, 86 mCRC patients were genotyped for study purposes. PBMCs harbouring the FcγRIIIa 158 V/V genotype had a significantly higher cetuximab-mediated ADCC. No correlation was found between FcγR polymorphisms and response rate or time to progression after cetuximab-based therapy. Despite the in vitro analysis showing that the FcγRIIIa 158 V/V genotype is associated with higher ADCC, clinical data do not support a predictive role of FcγRIIIa polymorphisms in mCRC treated with cetuximab.

Cross-presentation of IgG-containing immune complexes

IgG is a molecule that functionally combines facets of both innate and adaptive immunity and therefore bridges both arms of the immune system. On the one hand, IgG is created by adaptive immune cells, but can be generated by B cells independently of T cell help. On the other hand, once secreted, IgG can rapidly deliver antigens into intracellular processing pathways, which enable efficient priming of T cell responses towards epitopes from the cognate antigen initially bound by the IgG. While this process has long been known to participate in CD4(+) T cell activation, IgG-mediated delivery of exogenous antigens into a major histocompatibility complex (MHC) class I processing pathway has received less attention. The coordinated engagement of IgG with IgG receptors expressed on the cell-surface (FcγR) and within the endolysosomal system (FcRn) is a highly potent means to deliver antigen into processing pathways that promote cross-presentation of MHC class I and presentation of MHC class II-restricted epitopes within the same dendritic cell. This review focuses on the mechanisms by which IgG-containing immune complexes mediate such cross-presentation and the implications that this understanding has for manipulation of immune-mediated diseases that depend upon or are due to the activities of CD8(+) T cells.

Role of activating FcγR gene polymorphisms in Kawasaki disease susceptibility and intravenous immunoglobulin response

BACKGROUND

A functional polymorphism in the inhibitory IgG-Fc receptor gene FcγRIIB influences intravenous immunoglobulin (IVIG) response in Kawasaki disease (KD), a vasculitis preferentially affecting the coronary arteries in children. We tested the hypothesis that the polymorphisms in the activating receptors (FcγRIIA, FcγRIIIA, and FcγRIIIB) also influence susceptibility, IVIG treatment response, and coronary artery disease in patients with KD.

METHODS AND RESULTS

We genotyped polymorphisms in the activating FcγRIIA, FcγRIIIA, and FcγRIIIB using pyrosequencing in 443 patients with KD, including 266 trios and 150 single parent-child pairs, in northwest United States and genetically determined race with 155 ancestry informative markers. We used family-based association to test for transmission disequilibrium and further generated pseudosibling controls for comparisons with the cases. The FcγRIIA-131H variant showed an association with KD (P=0.001) with an additive odds ratio (OR) of 1.51 (95% CI, 1.16-1.96; P=0.002) for the primary combined population, which persisted in both white (P=0.04) and Asian (P=0.01) subgroups and is consistent with the recent genome-wide association study. We also identified overtransmission of the FcγRIIIB neutrophil antigen 1 (NA1) variant among IVIG nonresponders (P=0.0002) and specifically to white IVIG nonresponders (P=0.007). ORs for overall and white nonresponders were 3.67 (95% CI, 1.75-7.66; P=0.0006) and 3.60 (95% CI, 1.34-9.70; P=0.01), respectively. Excess NA1 transmission also occurred in patients with KD with coronary artery disease (OR(additive), 2.13; 95% CI, 1.11-4.0; P=0.02).

CONCLUSIONS

A common variation in FcγRIIA is associated with increased KD susceptibility. The FcγRIIIB-NA1 variant, which confers higher affinity for IgG than the NA2 variant, is a determining factor for treatment response. These activating FcγRs play an important role in KD pathogenesis and the IVIG antiinflammatory mechanism.

Characterization and allelic polymorphisms of rhesus macaque (Macaca mulatta) IgG Fc receptor genes

Macaque models are invaluable for AIDS research. Indeed, initial development of HIV-1 vaccines relies heavily on simian immunodeficiency virus-infected rhesus macaques. Neutralizing antibodies, a major component of anti-HIV protective responses, ultimately interact with Fc receptors on phagocytic and natural killer cells to eliminate the pathogen. Despite the major role that Fc receptors play in protective responses, there is very limited information available on these molecules in rhesus macaques. Therefore, in this study, rhesus macaque CD32 (FcγRII) and CD64 (FcγRI) homologues were genetically characterized. In addition, presence of CD16 (FcγRIII), CD32, and CD64 allelic polymorphisms were determined in a group of nine animals. Results from this study show that the predicted structures of macaque CD32 and CD64 are highly similar to their human counterparts. Macaque and human CD32 and CD64 extracellular domains are 88-90% and 94-95% homologous, respectively. Although all cysteines are conserved between the two species, macaque CD32 exhibits two additional N-linked glycosylation sites, whereas CD64 lacks three of them when compared to humans. Five CD32, three CD64, and three CD16 distinct allelic sequences were indentified in the nine animals examined, indicating a relatively high level of polymorphism in macaque Fcγ receptors. Together, these results validate rhesus macaques as models for vaccine development and antibody responses, while at the same time, underscoring the need to take into account the high degree of genetic heterogeneity present in this species when designing experimental protocols.

High-dose intravenous immunoglobulin (IVIG) therapy in autoimmune skin blistering diseases

Treatment of autoimmune bullous skin diseases can often be challenging and primarily consists of systemic corticosteroids and a variety of immunosuppressants. Current treatment strategies are effective in most cases but hampered by the side effects of long-term immunosuppressive treatment. Intravenous immunoglobulin (IVIG) is one potential promising therapy for patients with autoimmune bullous skin diseases, and evidence of its effectiveness and safety is increasing. A number of autoimmune bullous skin diseases have been identified in which IVIG treatment may be beneficial. However, experience with IVIG in patients with autoimmune skin blistering disease is limited, where it is recommended for patients not responding to conventional therapy. The mode of action of IVIG in autoimmune diseases, including bullous diseases is far from being completely understood. We here summarize the clinical evidence supporting the notion, that IVIG is a promising therapeutic agent for the treatment of patients with autoimmune bullous skin disease. In addition, we review the proposed modes of action. In the future, randomized controlled trials are necessary to better determine the efficacy and adverse effects of IVIG in the treatment of autoimmune bullous skin diseases. In addition, insights into IVIG's mode of action might enable us to develop novel therapeutics to overcome the current shortage of IVIG.

Natural autoantibodies: immune homeostasis and therapeutic intervention

The importance of natural autoantibodies reacting with self-antigens has long been neglected, as tolerance to self was believed to be primarily dependent on the deletion of autoreactive clones during ontogeny. However, it is now well established that autoreactive antibodies and B- and T-cells are present in healthy individuals. Research into the properties of natural autoantibodies and their role in immune homeostasis has been extensively investigated for a number of years. This information should lead towards the therapeutic exploitation of natural autoantibodies in the immunotherapy of autoimmune and inflammatory disorders.

Fcgamma receptor polymorphisms and their association with periodontal disease: a meta-analysis

AIM

A systematic review and a meta-analysis were conducted in order to investigate the potential association of Fcgamma receptor (FcgammaR) polymorphisms with susceptibility to aggressive and chronic periodontal disease.

MATERIALS AND METHODS

A database search yielded a total of 17 studies involving 1685 cases and 1570 controls. Three polymorphisms were included in the meta-analysis: FcgammaRIIA H131R (rs1801274), FcgammaRIIIA F158V (rs396991) and FcgammaRIIIB NA1/NA2. Random-effect models were used in the analysis. Odds ratios (ORs) along with their 95% confidence intervals (CIs) were computed to compare the distribution of alleles and genotypes between cases and controls.

RESULTS AND CONCLUSIONS

The FcgammaRIIIB NA1/NA2 polymorphism was associated with both aggressive (per-allele OR 2.005, 95% CI: 1.044, 3.851) and chronic periodontitis (recessive contrast NA2NA2 versus NA1NA1+NA1NA2 OR 1.397, 95% CI: 1.039, 1.878). The analysis showed weak evidence for association between the FcgammaRIIA H131R polymorphism and aggressive periodontitis in Asians (R versus H allele OR 1.579, 95% CI: 1.025, 2.432). On the contrary, no relationship was identified between FcgammaRIIIA F158V and periodontal disease. Accumulating evidence from basic research makes the suggested association between FcgammaRIIIB NA1/NA2 polymorphism and periodontitis biologically plausible. Further research, however, is needed in order to assess possible gene-gene or gene-environment interactions (i.e. with smoking).

Generation of a high-affinity Fcgamma receptor by Ig-domain swapping between human CD64A and CD16A

A recombinant soluble version of the human high-affinity receptor for IgG, rh-FcgammaRIA or CD64A, was expressed in mammalian cells and purified from their conditioned media. As assessed by circular dichroism, size exclusion chromatography and dynamic light scattering, incubation of rh-FcgammaRIA at 37 degrees C resulted in time-dependent formation of soluble aggregates caused by protein unfolding and loss of native structure. Aggregate formation was irreversible, temperature-dependent and was independent of rh-FcgammaRIA concentration. Aggregated rh-FcgammaRIA lost its ability to inhibit immune complex precipitation and failed to bind to IgG-Sepharose. Addition of human IgG1 to rh-FcgammaRIA prior to incubation at 37 degrees C blocked the formation of rh-FcgammaRIA aggregates. Production of soluble monomeric rh-FcgammaRIA was limited by aggregate formation during cell culture. Substitution of the membrane distal D1 Ig domain of FcgammaRIA with the D1 Ig domain of FcgammaRIIIA or CD16A resulted in a chimeric receptor, FcgammaR3A1A, with enhanced temperature stability. Relative to native rh-FcgammaRIA, FcgammaR3A1A exhibited less aggregation in Chinese hamster ovary cell-conditioned media or when purified receptor was incubated for up to 24 h at 37 degrees C. Both receptors bound to immobilized human IgG1 with high affinity and were equipotent at blockade of immune complex-mediated cytokine production from cultured mast cells. Equivalent dose-dependent reductions in edema and neutrophil infiltration in the cutaneous Arthus reaction in mice were noted for rh-FcgammaRIA and FcgammaR3A1A. These data demonstrate that the D1 Ig domains of FcgammaRIA and FcgammaRIIIA are functionally interchangeable and further suggest that the chimeric receptor FcgammaR3A1A is an effective inhibitor of type III hypersensitivity in mice.

Functional and clinical consequences of Fc receptor polymorphic and copy number variants

Receptors for immunoglobulins (Fc receptors) play a central role during an immune response, as they mediate the specific recognition of antigens of almost infinite diversity by leucocytes, thereby linking the humoral and cellular components of immunity. Indeed, engagement of Fc receptors by immunoglobulins initiates a range of immunoregulatory processes that might also play a role in disease pathogenesis. In the circulation, five main types of immunoglobulins (Ig) exist - namely IgG, IgA, IgE, IgM and IgD and receptors with the ability to recognize and bind to IgG (Fc gamma receptor family), IgE (Fc epsilon RI and CD23), IgA (CD89; Fc alpha/microR) and IgM (Fc alpha/microR) have been identified and characterized. However, it is astonishing that nearly all the known human Fc receptors display extensive genetic variation with clear implications for their function, thus representing a substantial genetic risk factor for the pathogenesis of a range of chronic inflammatory disorders.

B cell reductive therapy with rituximab in the treatment of rheumatoid arthritis

The approach to treating autoimmune disorders is currently undergoing a significant change in focus. As therapies are developed that are more precise in targeting the pathogenesis for these diseases, patients experience significantly fewer side effects. At the same time, as more precise therapies are discovered, the etiologies of these diseases become further elucidated. It is now widely accepted that B-lymphocytes play a significant role in the pathogenesis of various autoimmune diseases, the extent of which continues to be the focus of ongoing research. Rheumatoid arthritis is one such disease process that has been the focus of various B-lymphocyte-directed therapeutic trials. In this paper we review the current research available on rituximab as treatment for rheumatoid arthritis. This review details results from four main studies, as well as others, which used rituximab in at least one of the arms in treatment of rheumatoid arthritis. The results are promising and will likely lead to longer term studies as well as a potential focus on B cell subsets.

Association of Fcgamma receptor polymorphisms with adult onset Still's disease in Korea

OBJECTIVE

Fcgamma receptors (FcgammaR) have important functions in the regulation of immune response and clearance of immune complex. High levels of immunoglobulins have been observed in patients with the active stage of adult onset Still's disease (AOSD), and high-dose intravenous immunoglobulin treatment has decreased the disease activity of AOSD. We investigated polymorphisms of FcgammaR as genetic factors influencing susceptibility or disease course of AOSD in Korea.

METHODS

We genotyped the FcgammaRIIA H/R131, IIIA F/V176, and IIIB NA1/NA2 loci in 98 patients with AOSD and 151 healthy controls. Genotyping was performed using sequence-specific PCR. Patients with AOSD were subdivided into groups according to disease course: monocyclic systemic, polycyclic systemic, or chronic articular type. Allelic, genotypic, and haplotypic associations were analyzed by chi-square test.

RESULTS

No significant skewing in any of the 3 FcgammaR polymorphisms was found between Korean AOSD patients and controls. FcgammaRIIA R/R131 and R/H131 genotype in patients with chronic articular-type disease was more frequent than in controls (p = 0.006 and p(corr) = 0.018). No differences of genotypic and allelic frequencies were found between other disease course types and controls. Haplotype IIA R131-IIIA F176-IIIB NA2 was more frequent in AOSD patients than in controls (p = 0.021).

CONCLUSION

Although FcgammaR polymorphisms are not associated with development of AOSD in Koreans, the haplotype IIA R131-IIIA F176-IIIB NA2 may be associated with AOSD. Also, the FcgammaRIIA polymorphism may be associated with chronic articular-type AOSD. We need to identify whether these polymorphisms are associated with a response to anti-tumor necrosis factor agents in patients with AOSD.

Pharmacokinetic study and Fcgamma receptor gene analysis in two patients with rheumatoid arthritis controlled by low-dose infliximab

The main aim of this study is to investigate the pharmacokinetics of infliximab and Fcgamma receptor (FcgammaR) polymorphism in two patients with rheumatoid arthritis (RA) who were well controlled by low-dose infliximab. A 57-year-old woman (Patient 1) and a 67-year-old woman (Patient 2) had active RA despite methotrexate and prednisolone treatments. They improved after the addition of infliximab (3 mg/kg), but developed pneumonia and sepsis, respectively. Although the infliximab doses were reduced to 1.5 mg/kg and 1 mg/kg, respectively, clinical improvements were maintained. Blood samples were obtained at 1 h after infliximab administration and at eight weeks (just before the next dose). The elimination half-life was determined by the serum concentration of infliximab. We also analyzed the polymorphisms of FcgammaRIIA, FcgammaRIIIA, and FcgammaRIIIB for the genomic DNA samples from the two patients and three controls. Amplification of the FcgammaR-genomic regions in allotype-specific polymerase chain reactions was used to distinguish the genotypes. Decresed clearance of infliximab was proven by a pharmacokinetic study of these patients under low-dose infliximab therapy. 131H/H (FcgammaRIIA) and 176F/F (FcgammaRIIIA) were detected in both patients. NA1/NA2 and NA2/NA2 (FcgammaRIIIB) were detected in Patients 1 and 2, respectively. These patients were well controlled over the long term by low-dose infliximab. The mechanism of the reduced clearance of infliximab might possibly be explained in part by the FcgammaR polymorphisms.

B-cell-directed therapy for inflammatory skin diseases

The basic understanding of inflammatory dermatoses and autoimmune-mediated skin disorders has greatly advanced and broadened our understanding of underlying immune mechanisms that shape the complex network of chronic inflammation and autoimmunity. The new treatment options for psoriasis exemplify how new insights into (auto)immune responses, especially the role and function of various immune cells and proinflammatory cytokines, may lead to new therapeutic strategies. The concept of targeting B cells in autoimmune-mediated disorders is closely related to the discovery of autoantibodies and their cellular origin. However, the appreciation of B cells in autoimmunity has significantly changed and is not limited to their role as progenitors of autoantibody secreting plasma cells. Recent investigations of various inflammatory skin diseases, that is, autoimmune blistering disorders, collagen vascular diseases, and atopic dermatitis, actually support the concept that B cells might be as important as T cells in the etiopathogenesis of these disorders. The striking clinical improvement seen in patients with rheumatoid arthritis following B-cell depletion with the anti-CD20 mAb rituximab has tremendously catalyzed the interest in B-cell-targeted therapies in different autoimmune diseases. Future translational and clinical investigations are mandatory to precisely define the role and the contribution of impaired B-cell function in (auto)immune-mediated skin diseases.

[B-cell-depleting antibodies in skin diseases]

Basic insight into immune mechanisms, particularly the role and function of various immune cells and proinflammatory cytokines in the etiopathogenesis of inflammatory dermatoses and autoimmune skin disorders, has made possible the development of novel therapeutic strategies. Because of their properties as antigen presenting cells and progenitors of autoantibody-secreting plasma cells, B cells have a major impact in different autoimmune diseases and represent an important therapeutic target. The remarkable clinical improvement seen in patients with rheumatoid arthritis after treatment with the monoclonal anti-CD20 antibody, rituximab, has strongly augmented the interest in B-cell-targeted therapies in different autoimmune diseases. Future clinical and immunological investigations are mandatory to precisely define the contribution of impaired B-cell function in development and progression of autoimmune mediated skin disorders.

Ex vivo simulation of IgG Fc and T-cell receptor functions: an application to inflammatory bowel disease

BACKGROUND

Human leukocyte IgG Fc receptors (FcgammaR) and T-cell receptors (TCR) are primary molecules involved in inflammatory and immune pathways.

METHODS

These 2 receptors were stimulated in whole blood for 2-4 hours with immune complex and specific agonistic antibody, respectively, and various mRNAs were quantified by a method we developed previously.

RESULTS

FcgammaR stimulation induced tumor necrosis factor superfamily 2 (TNFSF2), TNFSF8, TNFSF15, interleukin 1B (IL1B), IL8, CCL chemokine 2 (CCL2), CCL3, CCL4, CCL11, CCL20, CXCL chemokine 1 (CXCL1), CXCL2, and CXCL3 mRNA, whereas TCR stimulation induced different subsets of mRNA such as TNFSF1, TNFSF2, TNFSF5, TNFSF6, TNFSF9, TNFSF14, IL6, CCL2, CCL8, CCL20, and CXCL10. Interestingly, respondents and nonrespondents were identified for each mRNA. When we applied this method to inflammatory bowel disease, the respondent populations of TCR-induced TNFSF2 (= TNFalpha), TNFSF5, TNFSF14, CCL2, CCL8, and CCL20 mRNA were significantly higher in Crohn's disease (CD) patients than in healthy controls or those with ulcerative colitis (UC). No difference was found for FcgammaR-mediated responses. The respondent population of TCR-induced TNFSF2 showed significantly (P = 0.05) higher incidence of multiple surgeries than did nonrespondents.

CONCLUSIONS

These data demonstrate an underlining hyperfunction of TCR in peripheral-blood leukocytes in CD patients. The ex vivo simulation demonstrates an underlining hyperfunction of TCR in peripheral-blood leukocytes in CD patients and may form the basis of a relatively noninvasive test for distinguishing these IBDs.

XLA-associated neutropenia treatment: a case report and review of the literature

X-linked agammaglobulinemia (XLA) is a primary B-cell deficiency syndrome with an incidence of 5 to 10 cases per million. The current treatment approach includes intravenous immunoglobulin and aggressive antibiotic regimens for infections. Besides recurrent infections, XLA patients may present with other manifestations, such as alopecia, enteropathy, amyloidosis, and neutropenia. Neutropenia, which has been shown in up to 25% of affected patients, might also contribute to the degree of severity of bacterial infections that have been reported in these cases. Here we present our experience with the granulocyte colony-stimulant factor, filgrastim (Neupogen), in the treatment of neutropenia in a 14-month-old child with XLA.

Anti-inflammatory actions of intravenous immunoglobulin

The remarkable success story of the therapeutic application of pooled immunoglobulin G (IgG) preparations from thousands of donors, the so-called intravenous IgG (IVIG) therapy, to patients with a variety of hematological and immunological disorders began more than half a century ago. Since then, the use of this primary blood product has increased constantly, resulting in the serious danger of shortages in supply. Despite its widespread use and therapeutic success, the mechanisms of action, especially of the anti-inflammatory activity, are only beginning to be understood. In this review, we summarize the clinical use of IVIG for different diseases and discuss recent data on the molecular mechanisms that might explain how this potent drug mediates its activity in vivo.

The use of i.v. IG therapy in dermatology

The intravenous administration of exogenous pooled human immunoglobulin (i.v. IG) was originally licensed as antibody replacement therapy in patients with primary immunodeficiencies and there are currently six FDA-approved uses for this agent. Despite a current lack of FDA approval, off-label treatment of a multitude of dermatologic disorders with i.v. IG has shown exciting potential for this unique treatment modality. The diseases successfully treated with i.v. IG include autoimmune bullous diseases, connective tissue diseases, vasculitides, toxic epidermal necrolysis, and infectious disorders (such as streptococcal toxic shock syndrome). Currently the biggest drawback in the consideration of i.v. IG therapy in dermatologic disorders is the lack of randomized controlled trials. Nevertheless, there is a significant body of evidence demonstrating the efficacy of i.v. IG in patients with dermatologic disorders that are resistant to treatment with standard agents. In summary, i.v. IG constitutes a valuable and potentially life-saving agent in managing patients with a variety of dermatologic disorders under the appropriate circumstances.

Ex vivo induction of mRNA in human whole blood as a new platform of drug and dietary supplement development

Purpose

We introduced a new concept of ex vivo gene expression analysis (Mitsuhashi, Clin Chem 53:148–149, 2007), where drug action was simulated under physiological conditions. This model system was applied to study various fields of drug development.

Materials and Methods

Heparinized human whole blood was incubated with drugs for less than 4h. The changes of specific mRNA were then quantified using the method we developed (Mitsuhashi, Tomozawa, Endo, and Shinagawa, Clin Chem 52:634–642, 2006).

Results

The mRNA quantitation method was used as a model system to study the following areas: (1) identification of respondents and non-respondents, (2) ex vivo compound screening, (3) determination of individually optimized doses, (4) drug-to-drug comparison, (5) assessment of leukocyte toxicity, (6) discovery of molecular targets, (7) assessment of the action of dietary supplements, and (8) characterization of respondents and non-respondents for various dietary supplements.

Conclusion

Since ex vivo assays are safe, a large number of healthy donors and disease patients can be recruited to identify individual-to-individual variations, which is not available from current preclinical study models. Although each system should be validated using a large number of samples, the ex vivo analysis will be a new tool for the development of drugs and dietary supplements in future.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-007-9510-2) contains supplementary material, which is available to authorized users.

Primary chronic cold agglutinin disease: an update on pathogenesis, clinical features and therapy

Chronic cold agglutinin disease (CAD) is a subgroup of autoimmune hemolytic anemia. Primary CAD has traditionally been defined by the absence of any underlying or associated disease. The results of therapy with corticosteroids, alkylating agents and interferon-a have been poor. Cold reactive immunoglobulins against erythrocyte surface antigens are essential to pathogenesis of CAD. These cold agglutinins are monoclonal, usually IgMκ auto antibodies with heavy chain variable regions encoded by the V_H4-34 gene segment. By flowcytometric and immunohistochemical assessments, a monoclonal CD20⁺κ⁺B-lymphocyte population has been demonstrated in the bone marrow of 90% of the patients, and lymphoplasmacytic lymphoma is a frequent finding. Novel attempts at treatment for primary CAD have mostly been directed against the clonal B-lymphocytes. Phase 2 studies have shown that therapy with the chimeric anti-CD20 antibody rituximab produced partial response rates of more than 50% and occasional complete responses. Median response duration, however, was only 11 months. In this review, we discuss the clinical and pathogenetic features of primary CAD, emphasizing the more recent data on its close association with clonal lymphoproliferative bone marrow disorders and implications for therapy. We also review the management and outline some perspectives on new therapy modalities.

Treatment for Churg-Strauss syndrome: induction of remission and efficacy of intravenous immunoglobulin therapy

Churg-Strauss syndrome (CSS) is characterized by the presence of asthma, eosinophilia, and small-vessel vasculitis with granuloma. It is a distinct entity, as determined from all classifications of systemic vasculitis. The poor prognostic factors in CSS are renal insufficiency, cardiomyopathy, severe gastrointestinal (GI) tract, and central nervous systems (CNS) involvement. The initial management of CSS should include a high dose of a corticosteroid: prednisone at 1 mg/kg/day or its equivalent for methylprednisolone with tapering over 6 months. In patients with severe or rapidly progressing CSS, the administration of methylprednisolone pulse at 1 g/body/day for 3 days is recommended. When corticosteroid therapy does not induce remission, or when patients have poor prognostic factors, immunosuppressive cytotoxic therapy is indicated. However, some patients with severe CSS often show resistance to conventional treatment. We think that IVIG therapy is a hopeful candidate for second-line treatment for CSS patients, particularly in the case of neuropathy and/or cardiomyopathy, which are resistant to conventional therapy. However, there is not much evidence supporting the effectiveness of IVIG in CSS, and the mechanisms underlying the action of IVIG remain unclear. Now we are performing clinical trials of IVIG therapy for CSS patients who are resistant to conventional treatment, through a nationwide double-blinded placebo-controlled study in Japan.

Inflammation and bone erosion are suppressed in models of rheumatoid arthritis following treatment with a novel Syk inhibitor

Spleen tyrosine kinase (Syk), a key mediator of immunoreceptor signaling in inflammatory cells, is essential for immune complex-mediated signal transduction initiated by activated receptors for immunoglobulin G. In collagen-induced arthritis, R788/R406, a novel and potent small molecule Syk inhibitor suppressed clinical arthritis, bone erosions, pannus formation, and synovitis. Serum anti-collagen type II antibody levels were unaltered, while the half-life of exogenous antibody was extended when co-administered with R406. Expression of the targeted kinase (Syk) in synovial tissue correlated with the joint level of inflammatory cell infiltrates and was virtually undetectable in treated rats. Syk inhibition suppressed synovial cytokines and cartilage oligomeric matrix protein (COMP) in serum, suggesting a sensitive and reliable biomarker for R406 activity. These results highlight the role of activating Fcgamma receptors in inflammatory synovitis and suggest that interruption of the signaling cascade with a novel Syk inhibitor may be a useful addition to immunosuppressive disease-modifying anti-rheumatic drugs currently used in the treatment of human autoimmune diseases such as rheumatoid arthritis.

High-dose intravenous immunoglobulins for the treatment of autoimmune mucocutaneous blistering diseases: evaluation of its use in 19 cases

BACKGROUND

The mainstay of therapy of autoimmune mucocutaneous blistering diseases has been prolonged high-dose systemic corticosteroids and immunosuppressive agents. Recently, high-dose intravenous immunoglobulin (IVIg) has been employed in selected cases, with excellent results in most of them.

OBJECTIVE

We sought to evaluate the outcome of the use of IVIg in patients with autoimmune mucocutaneous blistering diseases refractory to conventional therapy or with contraindications for it.

METHODS

We performed a retrospective analysis of clinical response to monthly cycles of IVIg in 19 patients affected with autoimmune mucocutaneous blistering diseases: 10 patients with pemphigus vulgaris (PV), 2 with pemphigus foliaceus (PF), 4 with mucous membrane pemphigoid (MMP), 2 with epidermolysis bullosa acquisita, and one with linear IgA bullous dermatosis.

RESULTS

Four (21%) of 19 cases presented a complete response (2 PV, 1 MMP and 1 epidermolysis bullosa acquisita). Five (26%) patients did not respond to the treatment (3 PV, 1 PF, 1 MMP). Ten patients (53%) had a partial response.

LIMITATIONS

This was a retrospective noncontrolled study with a heterogeneous group of patients.

CONCLUSION

The effectiveness of IVIg was inferior to that previously reported. This difference could be attributed to the preparations employed, the different severity of the disease, or individual responses in each patient dependent on Fc receptor gamma polymorphisms.

Intravenous immunoglobulin: an update on the clinical use and mechanisms of action

Initially used as a replacement therapy for immunodeficiency diseases, intravenous immunoglobulin (IVIg) is now widely used for a number of autoimmune and inflammatory diseases. Considerable progress has been made in understanding the mechanisms by which IVIg exerts immunomodulatory effects in autoimmune and inflammatory disorders. The mechanisms of action of IVIg are complex, involving modulation of expression and function of Fc receptors, interference with activation of complement and the cytokine network and of idiotype network, regulation of cell growth, and effects on the activation, differentiation, and effector functions of dendritic cells, and T and B cells.

B-cell activity of polyclonal antithymocyte globulins

Polyclonal antithymocyte globulins (AThG) are a subset of antilymphocyte antibody preparations derived from the sera of rabbits or horses immunized with unfractionated cells isolated from pediatric human thymi. In vivo, AThG preparations have been used to successfully treat antibody mediated rejection in kidney transplant recipients. In vitro, AThG can induce apoptosis of naïve and memory B cells and terminally differentiated plasma cells. The presence of B-cell reactive antibodies in AThG results from a thymic inoculum containing a significant percentage of CD20(+) B cells and CD138(+) plasma cells. In this paper, the experimental and clinical evidence supporting the B-cell activity of AThG preparations, and their mechanisms of action, are reviewed.

FcgammaR: The key to optimize therapeutic antibodies?

The binding of IgG to receptors for the Fc region of IgG (FcgammaR) is a critical step for the initiation and the control of effector immune functions. Activating FcgammaR induce antibody-dependent cell cytotoxicity (ADCC), endocytosis of immune complexes followed by antigen presentation, phagocytosis, and release of cytokines or pro-inflammatory mediators. By contrast, inhibitory FcgammaR regulate immune responses by inhibiting the activation of B lymphocytes, monocytes, mast cells and basophils, induced through activating receptors. Studies with FcgammaR-deficient mice support the critical role of the different FcgammaR in the in vivo functional effects of therapeutic monoclonal antibodies. Structural studies have provided detailed insights in the molecular mechanisms that govern IgG/FcgammaR interactions. The importance of the sugar components linked to asparagine 297 in the function of IgG has been also highlighted. These data have led to the engineering of a new generation of monoclonal antibodies for therapeutic use with optimized effector functions.

A phase 2 study of rituximab in combination with recombinant interleukin-2 for rituximab-refractory indolent non-Hodgkin's lymphoma

PURPOSE

The incidence of non-Hodgkin's lymphoma (NHL), the fifth most common malignancy in the United States, has increased over 70% in the last 30 years. Fifty percent to 75% of patients with low-grade or follicular NHL respond to rituximab therapy. However, responses are generally of limited duration, and complete responses are rare. Preclinical work suggests that human recombinant interleukin-2 (rIL-2; aldesleukin, Proleukin) enhances rituximab efficacy. Antibody-dependent cellular cytotoxicity (ADCC) is an important mechanism of action of rituximab. rIL-2 induces expansion and activation of Fc receptor (FcR)-bearing cells, thereby enhancing ADCC. Therefore, a large, multicenter phase 2 trial to assess the effects of rIL-2 on rituximab therapy in patients with rituxumab-refractory low-grade NHL was conducted.

EXPERIMENTAL DESIGN

The combination of rituximab and rIL-2 was studied in 57 patients with rituximab-refractory low-grade NHL (i.e., patients must have received a single-agent course of rituximab and showed no tumor response, or had a response lasting <6 months). I.V. rituximab was given at 375 mg/m(2) (weeks 1-4). S.C. rIL-2 was given thrice a week at 14 MIU (weeks 2-5) and at 10 MIU (weeks 6-9).

RESULTS

Rituximab plus rIL-2 combination therapy was safe and generally well tolerated, but responses were low. Fifty-seven patients were enrolled with 54 evaluable for response; however, only five responses (one complete and four partial) were observed. Correlative data indicate that rIL-2 expanded FcR-bearing cells and enhanced ADCC. However, other factors, such as FcgammaR polymorphisms in patients refractory to single-agent rituxumab and heterogeneous tumor biology, may have influenced the lack of clinical efficacy seen with this combination therapy.

CONCLUSIONS

rIL-2 expands FcR-bearing cellular subsets in vivo and enhances in vitro ADCC of rituxumab. However, these findings do not directly translate into meaningful clinical benefit for patients with rituxumab-refractory NHL.