Role of CD204-positive tumor-associated macrophages in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is endemic in southwestern Japan, the Caribbean basin, and parts of central Africa, and is considered to be caused by long-term Infection with human T-cell leukemia virus type I. CD204 is a scavenger receptor that is overexpressed on alternatively activated macrophages and is known to be overexpressed in tumor-associated macrophages (TAMs). CD206 is also considered a marker of alternatively activated macrophages. However, no studies have investigated CD206 and TAMs. In the present study, we investigated the significance of CD204(+) and CD206(+) TAMs in ATLL tissue samples. We also investigated the correlations with the Ki-67 labeling index (Ki-67LI) and the number of CD31(+) vessels. We found that the number and ratio of CD204(+) TAMs were closely associated with the Ki-67LI, which reflects lymphoma cell proliferation. The number of CD31(+) vessels was not correlated with the number or ratio of CD204(+) and CD206(+) TAMs. The number and ratio of CD204(+) and CD206(+) TAMs, number of CD31(+) vessels, and the Ki-67LI were not associated with the clinical outcome of patients with ATLL. Although further studies are necessary to uncover the detailed mechanisms of CD204 and lymphoma proliferation, these data may provide novel insight into the pathogenesis of ATLL.