Objective.A qualitative and quantitative analysis of the functional, antigen-specific B cell receptor repertoire of patients with rheumatoid arthritis (RA) in synovial and peripheral compartments.Methods. B cells were activated to grow and differentiate at high efficiency in vitro under limitingdilution conditions. Isotype and specificity of the secreted Ig were tested by enzyme-linked immunosorbent assay.Results. In contrast to peripheral B cells, most synovial B cells had already switched to IgG/IgA in vivo. The frequencies of B cells specifically recognizing foreign antigens were decreased within the synovial population, whereas the frequencies of B cells specific for type I1 collagen, mycobacterial heat-shock protein 60 (hsp60), or IgG Fc fragments were significantly increased, revealing a negative correlation in terms of frequencies.Conclusion. B cells specific for human type I1 collagen, hsp60, and IgG Fc fragments are produced and/or expanded locally within the affected joints of RA patients. Thus, the specific immune system is definitely involved in the local inflammatory and destructive processes.

Several HLA-DR alleles are genetically associated with rheumatoid arthritis. DRB1*0401 predominates in Northern Europe and has a characteristic 70QKRAA motif. This sequence contacts bound peptides and the TCR. Further interactions have been suggested with additional proteins during Ag loading. We explored the much stronger processing/presentation of full-length recombinant human acetylcholine receptor α subunit to a specific T cell clone by APC from DRB1*0401+ than *0408+ donors. Using DR*04 transfectants, we show that this difference results largely from the single Lys71↔Arg interchange (0401↔0408), which scarcely affects epitope binding, rather than from any other associated polymorphism. Furthermore, we proved our recombinant polypeptides to contain the Escherichia coli 70-kDa heat shock protein molecule DnaK and its requirement for efficient processing and presentation of the epitope by DRB1*0401+ cells. According to a recent report, 70-kDa heat shock protein chaperones preferentially bind to the QKRAA, rather than the QRRAA, motif. Variations between the shared epitope motifs QKRAA and QRRAA are emphasized by underlining. We propose that such interactions enhance the intracellular epitope loading of *0401 molecules. They may thus broaden immune responses to pathogens and at least partially explain the distinct contributions of DRB1*0401 and other alleles to disease predisposition.

B cell activating factor belonging to the TNF family (BAFF) and a proliferation inducing ligand (APRIL), and their receptors BAFF receptor (BAFFR), B cell maturation antigen (BCMA), and transmembrane activator and CAML interactor (TACI) are involved in the regulation of B cell homeostasis and differentiation. BAFF overexpression leads to systemic lupus erythematosus (SLE) in mice and elevated BAFF levels have been observed in human SLE and mouse models for SLE. Furthermore, genetic inactivation of TACI in mice results in a SLE-like phenotype. Based on our recent finding that TACI is mutated in patients with common variable immunodeficiency, of whom more than 30% suffer from autoimmune conditions, we analyzed TACI in humans with SLE. Sequence analysis of TNFRSF13b/TACI in 119 unrelated SLE patients revealed four variants: R20C in exon 1, R72H in exon 3, the silent variation c.327 G > A in exon 3, and A181E in exon 4. No significant association with any of these variants was found, when compared to the frequencies of the variants in a healthy control cohort. Furthermore, the mutated alleles R20C and R72H did not segregate with the SLE phenotype in familial cases of SLE. Thus, our evaluation of the coding region of TNFRSF13b/TACI did not reveal any deleterious or disease-associated mutations.

Objective. To study the expression of the chaperone family of J proteins in the synovial tissue of patients with rheumatoid arthritis (RA) or osteoarthritis. Methods. Rabbit antibodies specific for a synthetic peptide (pHSJ1: EAYEVLSDKHKREIYD), representing the most conserved part of all J domains thus far identified-among them the Drosophila tumor suppressor Tid56-were used in immunohistochemical analyses of frozen sections of synovial tissue and immuno-blotting of protein extracts of adherent synovial cells. IgG specific for Tid56 was also used. Results. Both antisera predominantly and intensely stained synovial lining cells from RA patients; other cells did not stain or stained only faintly. In immunoblots, anti-pHSJ1 specifically detected several bands with molecular weights of >74 kd (type I), 57-64 kd (type II), 41-48 kd (type III), and <36 kd (type IV). The strongest band detected in RA adherent synovial cells was the type II band, whereas in a B cell line, a type I band was prominent. Conclusion. Several potentially new members of the J family are described. The type II band represents the human homolog of the Drosophila Tid56 protein and is strongly expressed in RA synovial tissue.

Molecular imaging has witnessed an upsurge in growth, with positron emission tomography leading the way. This trend has encouraged numerous synthetic chemists to enter the field of 18F‐radiochemistry and provide generic solutions to address the well‐recognized challenges of late‐stage fluorination. This Minireview focuses on recent developments in the 18F‐labeling of aromatic substrates.