A retrovirus associated with a human leukemia, adult T-cell leukemia.

Abstract

Most human lymphoid malignancies are of B-lymphocyte origin. Lymphoma and leukemia of peripheral T-lymphocyte origin are more frequent in Japan than in the United States and Europe (T- and B-cell Malignancy Study Group 1981). Adult T-cell leukemia (ATL) was proposed by Takatsuki’et al. to be a new disease distinct from other known T-cell malignancies (Takatsuki’et al. 1977; Uchiyama’etal. 1977). Subsequently, much attention has been paid to this disease in Japan because of its characteristic neoplastic cell morphology, clinical and pathological features, and the endemic distribution of birthplaces of patients in southwestern Japan. Hanaoka’et al. (1979) characterized the cyto- logical and histological features of ATL. With accumulation of pathological and clinical findings on cases of ATL and nonleukemic pleomorphic T-cell lymphoma (one type of malignant T-cell lymphoma), these two diseases were included in one category called adult T-cell leukemia/lymphoma (ATLL) (Hanaoka’etal. 1982). However, the abbreviation “ATL”, not 7“ATLL”, will be used in this review for the sake of simplicity, unless otherwise stated. In 1980, over 100 cases of ATL were evaluated in a nationwide survey on T- and B-cell malignancies carried out with the Cooperation of 27 medical institutions in Japan (T- and B-cell Malignancy Study Group 1981). This survey clearly demon- strated the unusually high incidence of T-cell malignancies in Kyushu, in the southwest of Japan, compared with the total incidence of lymphoid malignancies: The incidence in all Japan was 49% of the total malignancies, whereas it was 70% in southwestern Japan, mainly due to the high incidence of ATL in this region. These results suggested the possible involvement of a microorganism or, more likely, a virus in this disease.