Staining for dipeptidyl aminopeptidase IV (DAP IV [EC: 3.4.14.5]) activity was applied to aspiration biopsy specimens or imprint preparations of surgical biopsy specimens from thyroid tumors. Material was obtained from 55 patients with histologically proven thyroid diseases: 9 with papillary carcinoma, 5 with follicular carcinoma, 11 with follicular adenoma, 13 with adenomatous goiter, 8 with Hashimoto's thyroiditis, and 9 with other benign conditions. Most tumor cells, follicular lumina in cell clusters, and intranuclear inclusions were strongly positive for DAP IV in all examples of papillary or follicular carcinoma. In contrast, only a few epithelial cells were labeled for DAP IV in follicular adenoma and adenomatous goiter. Some Hürthle cells in Hashimoto's thyroiditis also were positive for DAP IV. When a DAP IV scoring system based on the percentage of positive cells and staining intensity was used, all benign tissues except one (from a follicular adenoma) were found to have extremely low scores. These results indicate that staining for DAP IV activity is a simple but useful tool to aid in distinguishing benign from malignant thyroid neoplasms.

Monoclonal antibodies to dipeptidyl aminopeptidase IV (DAP IV, EC 3.4.14.5) were raised and selectively applied to paraffin-embedded sections of thyroid carcinoma. Five monoclonal antibodies were found to stain paraffin sections of thyroid carcinomas. Using one of these antibodies (44-4), we studied retrospectively aberrant expression of DAP IV in thyroid carcinoma to determine whether immunohistochemical staining with DAP IV antibody is useful in pathological diagnosis. In almost all cases of thyroid follicular and papillary carcinoma, tumour cells were positive (99.0 per cent) with DAP IV, whereas the cases of follicular adenoma showed a low incidence (27.1 per cent) of positive staining. Follicular adenoma with incomplete capsular invasion had a higher positive incidence (50 per cent) than follicular adenoma without incomplete capsular invasion (9.6 per cent). In positive staining cases previously diagnosed as benign tumours, 11 benign cases reacting positively with DAP IV were rediagnosed as carcinoma after re-examination of more thyroid paraffin block sections or serial sections. These findings suggest that DAP IV monoclonal antibody is very useful in distinguishing thyroid follicular carcinoma from follicular adenoma.

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Adult T-cell leukemia (ATL) is one of the most difficult diseases to treat because of severe underlying immune deficiency and metabolic disturbance. Interferon has potent antiviral, antiproliferative, and immunomodulating properties, and therefore, this may be a good agent to treat such immune deficient patients with peripheral T-cell leukemia. During a period from April 1984 to August 1985, six patients were treated with interferon-beta (IFN-beta), and interferon-gamma (IFN-gamma) was given to five patients. Three patients achieved partial remission by IFN-beta administration with a response duration of 1, 1.5, and 12 months respectively, whereas one complete remission and two partial responses were experienced by IFN-gamma treatment with 4, 4, and 2 months of response. Side effects of IFN-beta were similar to those of IFN-gamma including fever, chills, fatigue, mild hematologic depression, and transient hepatic enzyme abnormalities. These promising results warrant further well-designed clinical trials including combination with other agents or modalities of treatment.

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