B lymphocyte autoimmunity in rheumatoid synovitis is independent of ectopic lymphoid neogenesis

B lymphocyte autoimmunity plays a crucial role in the pathogenesis of rheumatoid arthritis. The local production of autoantibodies and the presence of ectopic lymphoid neogenesis in the rheumatoid synovium suggest that these dedicated microenvironments resembling canonical lymphoid follicles may regulate the initiation and maturation of B cell autoimmunity. In this study, we assessed experimentally the relevance of ectopic lymphoid neogenesis for B cell autoimmunity by a detailed structural, molecular, and serological analysis of seropositive and seronegative human synovitis. We demonstrate that synovial lymphoid neogenesis is a reversible process associated with inflammation which is neither restricted to nor preferentially associated with autoantibody positive rheumatic conditions. Despite the abundant expression of key chemokines and cytokines required for full differentiation toward germinal center reactions, synovial lymphoid neogenesis in rheumatoid arthritis only occasionally progresses toward fully differentiated follicles. In agreement with that observation, we could not detect Ag-driven clonal expansion and affinity maturation of B lymphocytes. Furthermore, ectopic lymphoid neogenesis is not directly associated with local production of anti-citrullinated protein Abs and rheumatoid factor in the rheumatoid joint. Therefore, we conclude that synovial lymphoid neogenesis is not a major determinant of these rheumatoid arthritis-specific autoantibody responses.

Enhanced AP-1 and NF-kappaB activities and stability of interleukin 8 (IL-8) transcripts are implicated in IL-8 mRNA superinduction in lung epithelial H292 cells

Inhibition of protein synthesis may result in superinduction of short-lived transcripts and has been attributed variably to stabilization of transcripts and/or increased gene transcription. Little is known about the kinetics of these processes and relevant transcriptional elements have not been identified. In this study, we describe superinduction of interleukin 8 (IL-8) mRNA, an important inflammatory mediator, in lung epithelial-like H292 cells and identify the underlying molecular mechanisms and their kinetics. Cycloheximide (CHI, 10 microg/ml), an inhibitor of protein synthesis, maximally increased IL-8 mRNA levels 30-fold in H292 cells. Tumour necrosis factor alpha (TNF-alpha), which induced IL-8 mRNA 3-fold, synergized with CHI causing a 150-fold increase at 6 h. CHI early on increased the stability of IL-8 mRNA (from 40 min in cells cultured with medium to more than 4 h with CHI). CHI also increased transcription as shown by transfection with IL-8 promoter constructs. Truncated and mutated constructs identified NF-kappaB and AP-1 binding sites as primary cis-acting elements in IL-8 gene transcription and IL-8 mRNA superinduction. Electrophoretic mobility shift assays indicated that CHI increased NF-kappaB and prolonged AP-1 DNA-binding activities and that the synergism of TNF-alpha and CHI on IL-8 mRNA expression was paralleled by a further increase of AP-1 DNA-binding activity. This synergism was still noticed when 4 h elapsed between the addition of CHI and that of TNF-alpha. Taken together, our results indicate that CHI interferes with both post-transcriptional and transcriptional repressive mechanisms of IL-8 mRNA expression.

Iron-binding proteins in sputum of chronic bronchitis patients with Haemophilus influenzae infections

Airway inflammation during infection is associated with increased transudation of serum proteins and increased production of protein by the airway epithelium. We therefore, assessed whether Haemophilus influenzae infections in patients with chronic bronchitis are associated with increased levels of transferrin and lactoferrin in the sputum compared to uninfected patients. Sputum sol phase and serum samples from 14 infected and 13 uninfected patients with chronic bronchitis and from 12 bronchial asthma patients were included in the study. The median Q-values (the concentration in sputum sol phase/the concentration in serum) x 10(3) of transferrin appeared increased in chronic bronchitis patients with an H. influenzae infection (26.0, n=13) compared to uninfected controls (9.5, n=11) and bronchial asthma patients (4.5, n=6). The ratio of the Q(transferrin)/Q(albumin) was >1 in infected chronic bronchitis patients, indicating local production of transferrin. Growth of H. influenzae was stimulated more in sputum from infected and uninfected patients with chronic bronchitis than in sputum from patients with bronchial asthma. The concentrations of lactoferrin were not significantly different in infected (n=14) and uninfected (n=13) chronic bronchitis patients and bronchial asthma patients (n=12) (median 137.4, 84.6, 87.1 mg x L(-1), respectively). We conclude that in patients with chronic bronchitis with Haemophilus influenzae infections, the levels of transferrin are increased and the levels of lactoferrin are not associated with infections.

Characterization of the cholesterol crystallization-promoting low-density particle isolated from human bile

BACKGROUND & AIMS

Biliary concanavalin A-binding glycoprotein (CABG) contains cholesterol crystallization-promoting activity that is not accounted for by the pronucleators that have been characterized in this fraction. The aim of this study was to isolate and characterize the missing activity.

METHODS

Biliary glycoprotein was isolated using concanavalin A-Sepharose. Promoting activity in CABG was purified using density gradient ultracentrifugation.

RESULTS

Activity in CABG separated into two fractions at low (1.08) and high (1.29) density, which showed different crystallization kinetics in a model bile. The high-density fraction had a late onset time (49.2 +/- 17.8 hours) but a high crystal growth rate (13.4 +/- 5.2 micrograms. mL-1.h-1). The low-density fraction had a rapid onset time (33.9 +/- 20.9 hours) but a slower growth rate (6.5 +/- 3.8 micrograms.mL-1 .h-1). The high-density fraction was not further characterized in this study. The low-density fraction contained solid particles consisting of lipid and very little protein, and the activity was fully pronase resistant. Delipidation of the low-density fraction removed all activity.

CONCLUSIONS

A potent pronase-resistant nucleation-promoting activity was activated from human bile and characterized. The low-density fraction may be responsible for the rapid nucleation in bile from typical patients with fast-nucleating gallstones.

Immunoglobulins and alpha 1-acid glycoprotein do not contribute to the cholesterol crystallization-promoting effect of concanavalin A-binding biliary protein

Human bile contains cholesterol crystallization-stimulating proteins that can be isolated by concanavalin A-Sepharose chromatography. In the past few years an increasing number of different pronucleating proteins have been identified in the concanavalin A-binding fraction. In this study we attempted to estimate the relative contribution of a number of these proteins to total concanavalin A-binding pronucleating activity. For this purpose, concanavalin A-binding glycoproteins were isolated from gallbladder bile samples from 12 patients with gallstones. The role of IgA, IgG and IgM and alpha 1-acid glycoprotein was investigated by means of immunoextraction. No decrease in crystallization-promoting activity was observed after precipitation of more than 98% of the different immunoglobulins. In addition, removal of more than 95% of alpha 1-acid glycoprotein from different concanavalin A-binding fractions had no significant effect on cholesterol crystallization-promoting activity. The influence of fibronectin was estimated by addition of physiological concentrations to a model bile system. At these concentrations fibronectin did not promote crystallization. From these data we conclude that immunoglobulins, alpha 1-acid glycoprotein and probably also fibronectin do not significantly contribute to total concanavalin A-binding activity.

Characterization of the content of occluded biliary endoprostheses

In an attempt to establish why biliary endoprostheses clog we analysed the contents of 21 occluded endoprostheses. The major components of the endoprosthesis sludge were protein (25%) and an insoluble residue (20%) which consisted mainly of plant fibers. Compared with bile the material was also rich in unconjugated bilirubin, while the major components of bile--bile acids and lecithin--accounted for only 15%. Although the sludge often contained some cholesterol crystals, no cholesterol gallstones or pigment or mixed stones were found. The material contained bacteria, but not in abundance. Scanning electron microscopy of the walls of clogged endoprostheses revealed adherence of amorphous material, probably protein. SDS-polyacrylamide gel electrophoresis of the protein fraction of the material from different endoprostheses showed a characteristic pattern. The material always contained two major bands of approximately 16 and 13 kDalton, which were not observed in corresponding bile samples. The 16 and 13 kDalton proteins bound most avidly to the endoprosthesis wall. We postulate that the initial phase in the clogging process is adsorption of proteins, after which other materials such as bacteria, fibers from food and unconjugated bilirubin bind to the wall of the endoprosthesis.

Two human IgM myeloma proteins with unusual specificities for streptococcal carbohydrate-associated epitopes

Five hundred and fifty human sera from patients with IgM myeloma or Waldenström's macroglobulinaemia were screened by a solid-phase enzyme-linked immunoassay for binding to the carbohydrate of group A streptococci (A-CHO). Two of them (AC8 and AC179) contained immunoglobulin, which bound specifically to A-CHO even at serum dilutions of 1:10(7). Using synthetic oligosaccharides coupled to protein for inhibition studies, the fine specificities of AC8 and AC179 were determined. AC179 is directed to alpha-linked rhamnose oligosaccharides. AC8 appears to be specific for N-acetyl-D-glucosamine (GlcNAc) side chains beta(1----2)-linked to rhamnose, whereas GlcNAc side chains in A-CHO are reported to be beta(1----3)-linked to the rhamnose backbone. Naturally occurring anti-A-CHO antibodies consist mainly of low-affinity antibodies to such beta(1----3)-linked GlcNAc. In contrast, both myeloma antibodies show more than 10 times higher relative affinities to A-CHO than antibodies prepared from normal human serum (anti-GlcNAc and anti-A-CHO, respectively) by selection for high affinity in the elution procedure. AC179 induced complement activation in the presence of A-CHO.