No abstract

SUMMARYThyroglobulin (Tg) is a target autoantigen in autoimmune thyroid diseases, such as Graves' disease (GD) and Hashimoto's thyroiditis. In a previous study we identified three 20mer Tg peptides bearing epitopes of autoantibodies associated with GD (TgP15, TgP26 and TgP41: sequences 2339-2358, 2471-2490 and 2651-2670 of human Tg, respectively). In the present study, we investigated the antigenicity of the above peptides in experimental immunization with Tg, the immunogenicity of antigenic peptides and the possibility of intramolecular B-cell epitope spreading during peptide immunization. For this purpose, two rabbits were injected with human Tg in CFA six times, every three weeks. Two control animals were injected only with CFA. Testing of antisera and of affinity-purified antibodies, by ELISA against the three peptides, revealed reactivity only to TgP41. This synthetic peptide was subsequently administered to two rabbits, in its free form (100 m g in CFA six times, every two weeks). A strong serological response was developed not only against TgP41, but also to intact human and rabbit Tg. Immunization with TgP41 induced intramolecular B-cell epitope spreading, i.e. production of antibodies to sites on Tg other than that corresponding to TgP41, as revealed by immunoadsorption and competitive ELISA. Histopathological studies did not reveal any infiltration in thyroid glands. We conclude that peptide TgP41 encompasses not only an epitope of disease-associated autoantibodies, but also a dominant immunogenic epitope of experimentally induced Tg-specific antibodies, able to drive B-cell epitope spreading.

Background: Altered thrombocyte morphology and function have been reported in patients with diabetes mellitus (DM) type 2. The aim of the present study was to determine the associations between platelet morphology markers and hemoglobin A1C (HbA1c), fasting glucose (FG), hypertension and coronary heart disease (CHD) in patients with myelodysplastic syndromes (MDS) and DM, in patients with DM and in controls. Methods: This cross-sectional study included 30 cases with primary MDS with normal platelet count and non-insulin dependent diabetes, 30 non-insulin dependent diabetic patients and 30 non-diabetic, non-MDS controls matched on age and gender. Results: After adjusting for body mass index, platelet number, CHD and hypertension, HbA1c and FG were significant predictors of mean platelet volume (MPV) and platelet distribution width (PDW) in diabetic patients. There was no correlation between platelet parameters and HbA1c or FG in diabetic MDS patients. In controls, FG and hypertension predicted significant differences in platelet morphology. Platelet count correlated with platelet morphology in diabetic MDS and control groups, but not in diabetics. Conclusions: MPV and PDW are associated with glycemic indices in diabetic patients but not in diabetic MDS patients with normal platelet counts. Non-diabetic controls also exhibit FG related changes in platelet morphology. This suggests other factors inherent to bone marrow dysplasia, platelet turnover and biochemistry, or vascular environment affect platelet morphology in diabetic MDS patients even with normal platelet count. Platelet morphology in this population may be an early marker for myelodysplasia. These findings also support platelet morphology change as a marker for elevated macrovascular disease risk.

Objective: Thyroglobulin (Tg) is a large autoantigen involved in autoimmune thyroid diseases. Tg epitopes have, so far, been identi®ed within large peptides. In the present study, we used small synthetic peptides to ®nely map serological epitopes on the highly immunogenic C-terminal region of Tg. Homology of this region to acetylcholinesterase (AChE) has been implicated in the pathogenesis of thyroid eye disease (TED) through cross-reactive antibodies. Methods: We tested total IgG puri®ed from four pilot Graves' disease (GD) sera reactive with both Tg and AChE and from three healthy controls, for reactivity against overlapping 20mer peptides (pin synthesis) covering the sequence 2171±2748 of human Tg. Antibody-reactive peptides were subsequently synthesized by a solid-phase technique for con®rmation with a large number of sera: 99 GD, 32 Hashimoto's thyroiditis (HT) and 45 healthy controls. Results: Peptides TgP15, TgP26 and TgP41 (amino acids 2339±2358, 2471±2490 and 2651±2670 respectively) were found to be targets of autoantibodies on intact Tg, recognized by a statistically signi®cant proportion of GD sera (22.2%, 35.4% and 30.3% respectively), compared with HT (0%, 15.6% and 6.3% respectively) and healthy controls (0%, 4.4% and 4.4% respectively). The majority of GD sera (56.6%) were positive for at least one of the three peptides. In GD, TgP26 reactivity was found to be associated with TED (48.6% with TED versus 25.5% without TED, P , 0X05X Conclusion: Some epitopes on the C-terminal region of Tg are associated with GD. A subset of Tgreactive autoantibodies, directed to this region, is associated with TED and may be involved in the development of the disease.