Immunohistochemical study of necrotizing lymphadenitis: A possible mechanism for apoptosis involving perforin and granzyme-producing cytotoxic T cells

Twelve lymph node specimens with necrotizing lymphadenitis and which had florid necrotic lesions were studied immunohistochemically. The majority of viable lymphoid cells in the necrotic foci were CD8(+) lymphocytes and KP1(+) or PGM1(+) phagocytizing macrophages. The CD8(+) T cells were Leu1(+), Leu2(+), Leu3(-), Leu4(+), Leu5b(+), Leu7(-), Leu11b(-) and Leu19(-), indicating a suppressor/cytotoxic T cell phenotype. In addition, the cytoplasm of these cells was immunoreactive for perforin and granzyme a in a granular pattern. With a nick end-labeling technique, fragmented nuclei and some lymphoid cell nuclei were positively stained. These results suggest that the necrosis in necrotizing lymphadenitis is apoptotic necrosis of T cells targeted by CD8(+), perforin and granzyme-producing, activated cytotoxic T cells, supporting a viral infection etiology.