DNA fragmentation induced by
endonucleases is a hallmark of apoptotic process. One of the
endonucleases responsible for apoptotic DNA fragmentation has been identified as
DNase gamma. It has been suggested that massive nuclear debris observed in
histiocytic necrotizing lymphadenitis (HNL,
Kikuchi disease) results mainly from apoptosis of T-lymphocytes rather than
necrosis. To identify the role of
DNase gamma in apoptotic foci of HNL
paraffin embedded tissue sections of HNL and
lymphadenopathy with hyperplastic germinal centers and paracortex in the neck lymph nodes were immunohistochemically stained for
DNase gamma and the results compared with the reactivity of TdT-mediated dUTP nick end labeling (TUNEL). Immunoreactivity for
DNase gamma was detected in fragmented and condensed nuclei found abundantly in HNL as well as TUNEL reactivity. Moreover, the ratio of
DNase gamma immunoreactivity to TUNEL reactivity, which represents probability of apoptosis relevant to
DNase gamma, was higher in foci of nuclear debris in HNL than in the hyperplastic paracortex in
lymphadenopathy including T-cell apoptosis. Our findings suggest that apoptosis detected in HNL depends more specifically upon
DNase gamma than apoptosis in the hyperplastic paracortex of
lymphadenopathy, and that the dysregulation of
DNase gamma activation is involved in apoptosis in HNL.