Mark D. Jansen

Relevance of Fcγ Receptor and Interleukin-10 Polymorphisms for Meningococcal Disease

The contribution of individual Fcgamma receptor (FcgammaR) subclasses to meningococcal phagocytosis was studied. In addition, functional FcgammaR polymorphisms were determined in 50 patients with meningococcal disease (MD), in 183 first-degree relatives of MD patients, and in 239 healthy control subjects, to study the association of FcgammaR genotypes with disease. Efficient internalization of opsonized Neisseria meningitidis serogroup B was mediated via multiple FcgammaR subclasses on phagocytes. Accordingly, a low-efficiency combination of FcgammaRIIa-R/R131, FcgammaRIIIa-F/F158, and FcgammaRIIIb-NA2/2 genotypes was increased significantly in relatives of patients with MD, compared with healthy control subjects (P<.05; odds ratio, 2.6; 95% confidence interval, 1.1-6.3). FcgammaRIIa and FcgammaRIIIa genotype distributions differed between patients with sepsis and those with meningitis. Combined genotypes of FcgammaRIIa and interleukin-10 -1082, which was previously reported as being associated with MD outcome, were distributed randomly in control subjects but not in relatives of patients with MD (P<.01). These data provide further evidence for the association of polymorphic genes on chromosome 1 and MD.

Activity of Human IgG and IgA Subclasses in Immune Defense Against Neisseria meningitidis Serogroup B

Both IgG and IgA Abs have been implicated in host defense against bacterial infections, although their relative contributions remain unclear. We generated a unique panel of human chimeric Abs of all human IgG and IgA subclasses with identical V genes against porin A, a major subcapsular protein Ag of Neisseria meningitidis and a vaccine candidate. Chimeric Abs were produced in baby hamster kidney cells, and IgA-producing clones were cotransfected with human J chain and/or human secretory component. Although IgG (isotypes IgG1–3) mediated efficient complement-dependent lysis, IgA was unable to. However, IgA proved equally active to IgG in stimulating polymorphonuclear leukocyte respiratory burst. Remarkably, although porin-specific monomeric, dimeric, and polymeric IgA triggered efficient phagocytosis, secretory IgA did not. These studies reveal unique and nonoverlapping roles for IgG and IgA Abs in defense against meningococcal infections.

Fcγ 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 (FcγR) 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 FcγRIIa, 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 FcγRIIa, IIIa, and IIIb polymorphisms. Associations between FcγR genotypes, combined genotypes and clinical as well as laboratory features were analysed. Results: No significant skewing of any of the three FcγR 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 FcγRIIa, IIIa (double negative phenotypes) and FcγRIIa, 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 FcγRIIa/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.

A novel PCR-based method for direct Fcγ receptor IIIa (CD16) allotyping

Abstract Leukocyte IgG receptors (FcγR) are important immune-response modulating molecules. FcγRIIIa is expressed on macrophages, NK-cells and γδ-T cells and exhibits a genetically determined, functional polymorphism at nucleotide 559. This allelic difference predicts either a phenylalanine (F158) or valine (V158) at amino acid 158 in the membrane-proximal extracellular domain, and has been shown to be associated with autoimmune and infectious diseases. Published methods to determine FcγRIIIa genotypes are cumbersome. Therefore, we developed a novel, rapid and reliable PCR-based method to determine FcγRIIIa genotypes. Comparison of genotyping results with direct FcγRIIIa sequencing of 60 blood donors showed 100% accuracy of this new method. Since genotype frequencies of FcγR polymorphisms depend strongly on race and ethnicity, we compared FcγRIIIa genotype frequencies of 176 Caucasian Dutch and 104 Japanese blood donors. Interestingly, these frequencies were not significantly different (P>0.1), in contrast to the FcγRIIa and FcγRIIIb genotype frequencies (P

Pathogenicity of anti-ganglioside antibodies in the Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is a postinfectious inflammatory polyradiculo-neuropathy characterized by flaccid paralysis. Antibodies directed against glycolipid structures (gangliosides), which are highly expressed in the peripheral nervous system, are frequently detected in sera from GBS patients. These antibodies interfere with nerve conduction and have been shown to activate phagocytes via IgG receptors (FcgammaR). These findings support an important role of glycolipid-specific antibodies in the pathogenesis of GBS.

46 - Infection and Guillain-Barré syndrome

Guillain-Barre syndrome (GBS) is a postinfectious polyradiculoneuropathy. Molecular mimicry between microbial structures and glycolipids (gangliosides) on peripheral nervous tissue is thought to elicit a ganglioside-specific immune response, resulting in localized inflammation and tissue damage. Although experimental evidence supports a role for anti-ganglioside antibodies in GBS pathogenesis, the mechanisms, which eventually trigger the production of cross-reactive antibodies in a small percentage of individuals, have remained elusive. Gangliosides are sialic acid-containing glycolipid structures, consisting of a hydrophobic ceramide moiety, anchored in the cell membrane, and linked to externally exposed hydrophilic carbohydrate structures. Host and pathogen characteristics, which contribute to the development of this monophasic autoimmune disorder, remain to be identified. This chapter aims at providing an overview of the role of anti-ganglioside antibodies in the pathogenesis of GBS, as well as describing the possible interaction of pathogens with the immune system, leading to an induction of pathogenic antibodies.