Marguerite-Marie Boutillon

A recurrent Vα17 / Vβ10 TCR-expressing T cell clone is involved in the pathogenicity of collagen-induced arthritis in DBA / 1 mice

Collagen‐induced arthritis (CIA) is an experimental model that mimics clinical and histological features of rheumatoid arthritis. In this disease, a crucial role in initiating the pathological changes has been assigned to T lymphocytes expressing the Th1 phenotype. Aiming at identifying type II collagen (CII)‐specific T cells involved in CIA, T cell clones were generated in vitro from the lymph nodes (LN) of CII‐immunized DBA / 1 mice. In three independent experiments, we repeatedly isolated CD4+ Th1 clones recognizing the immunodominant epitope in the CB11 fragment of bovine CII and expressing a unique α βTCR produced by the rearrangement of Vα17 / Jα20 and Vβ10 / Dβ1.1 / Jβ2.5 gene segments. By reverse transcriptase‐PCR, we demonstrated the presence of mRNA transcripts specific for the β complementary‐determining region 3 of this clonotype in the LN of the majority (73 %) of mice with CIA whereas it was never detected in control animals. When transferred to CII‐immunized DBA / 1 mice, this recurrent Th1 clone augmented the incidence, aggravated significantly the clinical signs of CIA and greatly enhanced the anti‐CII antibody response. Altogether, these results provide evidence that a CD4+ Th1 clone belonging to the public arm of the response toward the immunodominant epitope of CII is involved in the cascade of events leading to CIA.

Lymphatic Transport of Cholesterol from Exogenous and Biliary Origins in Nonfasting Rats After Intraduodenal Infusions of Triolein

Labelled thoracic-duct lymph was collected from nonfasting rats with a bile fistula after simultaneous intraduodenal infusions of bile labelled with [1-2 3H] cholesterol and a nutritive mixture containing [4-14C] cholesterol. The gastrointestinal tract, feces, chylomicrons and infranatants were analysed. Both biliary and exogenous cholesterol were absorbed by lymphatic way but the recovery of 3H labelling in total lymph was markedly higher than that of 14C activity. This fact might be due to different rates of cholesterol exchanges from the two origins with the nonlabelled cholesterol present in the enterocytes and further exchanges of the enterocytes cholesterol with plasma cholesterol. Most of radioactivity was detected in chylomicrons. The relative [3H] and [14C] cholesterol specific activities were always low; thus when a little exogenous cholesterol is brought the major part of lymph cholesterol had an endogenous--other than biliary--source.

Structural requirements for fibromodulin binding to collagen and the control of type I collagen fibrillogenesis

Fibromodulin belongs to the family of small, leucine-rich proteoglycans which have been reported to interact with collagens and to inhibit type I collagen fibrillogenesis. Decorin and fibromodulin exhibit a noticeable degree of sequence similarity. However, as previously reported [Font, B., Eichenberger, D., Rosenberg, L. M. & van der Rest, M. (1996) Matrix Biol. 15, 341-348] the domains of these molecules implicated in the interactions with type XII and type XIV collagens are different, these being the dermatan sulphate/chondroitin sulphate chain for decorin and the core protein for fibromodulin. At the present time the fibromodulin domains implicated in the interactions with fibrillar collagens remain unknown. In experiments reported here, we have sought to identify the structural requirements for fibromodulin interaction with collagen and for the control of type I collagen fibrillogenesis. Circular dichroism spectra and fibrillogenesis inhibition studies show that fibromodulin structure and its collagen fibrillogenesis control function are strictly dependent on the presence of intact disulphide bridge(s). In addition, we show that the binding of fibromodulin (or fibromodulin-derived fragments) to type I collagen is not necessarily correlated with fibrillogenesis inhibition. To isolate fibromodulin domains, the native proteoglycan was submitted to mild proteolysis. We have isolated an alpha-chymotrypsin-resistant fragment which contains the bulk of the N-terminal and central region of the molecule including the leucine-rich repeats 4 and 6 reported for decorin to be involved in type I collagen binding. This fragment does not bind to type I collagen. Using enzymes with different specificities, a number of large fragments of fibromodulin were obtained, suggesting a compact structure for this molecule which is relatively resistant to proteolysis. None of these N-glycosylated fragments were able to bind to type I collagen in co-sedimentation experiments. Taken together these results suggest that fibromodulin-type I collagen interactions leading to fibrillogenesis inhibition require more than one binding domain. One of these domains could be the C-terminal end of the molecule containing the disulphide loop which is absent in the chymotrypsin-resistant fragment.