Plasmacytoid Dendritic Cells Producing Interferon-α (IFN-α) and Inducing Mx1 Play an Important Role for CD4⁺ Cells and CD8⁺ Cells in Necrotizing Lymphadenitis

Abstract

　 We confirmed the characteristic clinical features of necrotizing lymphadenitis (NEL) in 66 cases (23 male, 43 female) in Japan, which included high fever (38-40°), painful cervical lymphadenopathy (62/66, 93.9%), and leukopenia (under 4,000/mm³) (25/53, 47.2%), without seasonal occurrence, in a clinicopathological, immunohistochemical, electron microscopic serological study. Patient age varied from 3-55 years, and 72.7% (44/66) of patients were younger than 30 years. Histopathology of NEL was characterized by the presence of CD8⁺ immunoblasts, CD123⁺ cells (plasmacytoid dendritic cells; PDCs), histiocytes and macrophages phagocytizing CD4⁺ apoptotic lymphocytes, but no granulocytes or bacteria. The number of PDCs and CD8⁺ cells in lesions tended to increase with time, and PDCs tended to be larger and irregular in the lesions compared with the non-lesion tissue of the lymph nodes. In addition, PDCs showed no temporal morphological change in the lymph nodes. The number of CD4⁺ cells in the lymph node lesions sharply decreased from the 2nd to the 4th week, and then tended to increase; however, CD4⁺ cells gradually decreased with time in non-lesion tissue. PDCs may produce interferon-α (IFN-α), which induces Mx1 expression. Strong Mx1 immunoreactivity is indicative of IFN-α production. IFN-α induces transformation of CD8⁺ cells into immunoblasts, as well as phagocytosis of apoptotic cells derived from CD4⁺ cells by macrophages. Thus, PDCs may play an important role with immune cells, including CD8⁺ and CD4⁺ cells, in necrotizing lymphadenitis. [J Clin Exp Hematop 55(3) : 127-135, 2015]