Majida Bouanani

Human Anti-Thyroid Peroxidase Single-Chain Fragment Variable of Ig Isolated from a Combinatorial Library Assembled In-Cell: Insights into the In Vivo Situation

In an attempt to explore the natural variable heavy and light chain (VH/VL) pairing of autoantibodies involved in Graves’ disease, we constructed a phage-displayed Ab library obtained by in-cell PCR of thyroid-infiltrating cells. We report here the molecular cloning and characterization of human single-chain fragment variable regions (scFv) specific for thyroid peroxidase (TPO) generated from this library. On the basis of the nucleotide sequences, three different scFvs were obtained (ICA1, ICB7, and ICA5). All were encoded by genes derived from the VH1 and Vλ1 gene families. Using BIACORE for epitope mapping and kinetic analysis, we showed that these scFvs exhibited high affinity (Kd = 1 nM) for TPO and recognized three different epitopes. The biological relevance of these scFvs as compared with serum anti-TPO autoantibodies was assessed by competition studies. Sera from all the 29 Graves’ disease patients tested were able to strongly inhibit (60–100%) the binding of the 3 scFvs to TPO. These data demonstrate that the in-cell PCR library generated human anti-TPO scFvs that retained the VH/VL pairing found in vivo and that the different epitope specificities defined by these scFvs overlapped with those found in the sera of patients with autoimmune thyroid disease.

Factors Involved in Catheter Obstruction During Long-Term Peritoneal Insulin Infusion

OBJECTIVE To analyze the efficacy of ECPII and the factors responsible for technical problems often encountered. This treatment has been in use with IDDM patients since 1980. RESEARCH DESIGN AND METHODS Forty-four IDDM treated by ECPII for 42–78 mo (mean, 53 mo). patients were RESULTS Glycemic equilibrium was improved during treatment (mean plasma glucose level, 7.6 mM; mean GHb level, 8%). Catheter blockage was the main reason for ECPII failure (74%). Mean catheter survival of each catheter, determined by actuarial analysis, was 11.7 mo and significantly decreased with subsequent implantation. SEM of the catheter tips showed deposits composed of fibrin and cells occluding the inner lumen. Factors such as age, sex, local infection, and low insulin basal rate were not found to have any incidence on the catheter survival. Placement of the catheter in the upper part of the peritoneum, however, increased catheter survival. Anti-insulin antibodies did not seem to be directly involved in blockage. CONCLUSIONS We conclude from this long-term experience that during ECPII, catheter blockage remains the major recurring complication, probably involving a local immune-inflammatory response in the peritoneum.