C-terminal citrullinated peptide alters antigen-specific APC:T cell interactions leading to breach of immune tolerance.

In rheumatoid arthritis, the emergence of anti-citrullinated autoimmunity is associated with HLA-antigen-T cell receptor complexes. The precise mechanisms underpinning this breach of tolerance are not well understood. Porphyromonas gingivalis expresses an enzyme capable of non-endogenous C-terminal citrullination with potential to generate citrullinated autoantigens. Here we document how C-terminal citrullination of ovalbumin peptide323-339 alters the interaction between antigen-presenting cells and OTII T cells to induce functional changes in responding T cells. These data reveal that C-terminal citrullination is sufficient to breach T cell peripheral tolerance in vivo and reveal the potential of C-terminal citrullination to lower the threshold for T cell activation. Finally, we demonstrate a role for the IL-2/STAT5/CD25 signalling axis in breach of tolerance. Together, our data identify a tractable mechanism and targetable pathways underpinning breach of tolerance in rheumatoid arthritis and provide new conceptual insight into the origins of anti-citrullinated autoimmunity.

Inhibition of Aerobacter cephalosporin beta-lactamase by penicillins.

Cephalosporinase (beta-lactamase) was obtained from cell washings of Aerobacter (Enterobacter) cloacae as a highly active preparation. An alkalimetric method was used to determine the enzyme activity and to estimate its inhibition by 6-amino-penicillanic acid derivatives. Their order of decreasing inhibitory effect was as follows: cloxacillin, oxacillin, methicillin, ampicillin, and penicillin G. We found that 2 to 3 ng of cloxacillin per ml was sufficient to decrease the enzyme activity by 50% in the presence of 400 mug of cephalosporin C per ml. Cloxacillin exerted a potentiating effect on the inhibition of the E. cloacae organisms by cephalosporin C.

Plasma catecholamine levels in normal subjects and in patients with secondary hypertension.

We compared normal values for human venous norepinephrine (NE) and epinephrine (E) as reported in the literature with values determined in this laboratory and we measured and contrasted NE levels in patients with primary and secondary hypertension. Analysis of published data from many laboratories involving more than 800 supine, resting, healthy subjects indicated an average circulating level of venous NE of 260 pg/ml and of E, about 35 pg/ml. Supine levels of NE normally double when normal subjects stand for 5 min. This simple test provides one assessment of overall sympathetic nervous system integrity. Levels of catecholamines have been extensively studied in essential hypertension but much less so in secondary hypertension. Of the groups we studied with secondary hypertension (diabetes mellitus, primary hyperaldosteronism, polycystic kidney disease, chronic bilateral renal parenchymal disease, and unilateral renal arterial stenosis), only the group with renal parenchymal disease had supine NE levels significantly higher than the control group. Patients with essential hypertension and diabetes had a blunted increase in NE on standing. Plasma levels of NE do not reliably differentiate these groups of secondary hypertension from one another or from patients with primary hypertension.

Cloning and characterization of muscle-specific kinase in chicken.

Muscle-specific kinase (MuSK) is part of the receptor complex that is involved in the agrin-induced formation of the neuromuscular junction. In the rodent, prominent mRNA expression of MuSK is restricted to skeletal muscle while the expression of agrin can also be detected in brain and certain nonneuronal tissues. The recent identification of Xenopus MuSK reveals that MuSK can be detected in tissues other than skeletal muscle, such as the neural tube, eye vesicles, and spleen. In this study, we describe the cloning and characterization of the chicken ortholog of MuSK and demonstrate that the regulation of MuSK expression in muscle is conserved from avian to rodent. Abundant mRNA expression of MuSK can be detected in early embryonic chick muscle and is up-regulated after nerve injury. More importantly, we also demonstrate that, in the chicken, MuSK mRNA is expressed during development in brain and liver, suggesting possible novel functions for MuSK. Furthermore, the regulatory profile of MuSK expression in chick muscle closely parallels that observed for acetylcholine receptor, in terms of both mRNA expression and protein localization. Finally, studies with paralyzed chicken muscle as well as with cultured chick myotubes demonstrate the dependence of MuSK on both electrical activity and trophic factors.