EXPRESSION OF HUMAN HERPESVIRUS-6 ANTIGENS IN BENIGN AND MALIGNANT LYMPHOPROLIFERATIVE DISEASES

Immunohistochemistry was used to look for the expression of human herp esvirus-6 (HHV-6) antigens in a well characterized series of benign, a typical, and malignant lymphoid lesions, which tested positive for the presence of HHV-6 DNA, A panel of specific antibodies against HHV-6 a ntigens, characteristic either of the early (p41) or late (p101K, gp10 6, and gp116) phases of the viral cycle, was applied to the lymphoid t issues from 15 non-Hodgkin's lymphomas, 14 Hodgkin's disease cases, 5 angioimmunoblastic lymphadenopathies with dysproteinemia, 14 Reactive lymphadenopathies, and 2 cases of sinus histiocytosis with massive lym phadenopathy (Rosai-Dorfman disease). In lymphomatous tissues, the exp ression of late antigens was documented only in reactive cells, and ma inly in plasma cells. Of interest, the expression of the early p41 ant igen was detected in the so-called ''mummified'' Reed-Sternberg cells, in two Hodgkin's disease cases. In reactive lymphadenopathies, the HH V-6 late antigen-expressing cells were plasma cells, histiocytes, and rare granulocytes distributed in interfollicular areas. In both cases of Rosai-Dorfman disease, the p101K showed an intense staining in foll icular dendritic cells of germinal centers, whereas the gp106 exhibite d an intense cytoplasmic reaction in the abnormal histiocytes, which r epresent the histological hallmark of the disease. The expression of H HV-6 antigens is tightly controlled in lymphoid tissues. The lack of H HV-6 antigen expression in neoplastic cells and the limited expression in degenerating Reed-Sternberg cells argue against a major pathogenet ic role of the vines in human lymphomagenesis, The detection of a rath er unique pattern of viral late antigen expression in Rosai-Dorfman di sease suggests a possible pathogenetic involvement of HHV-6 in some ca ses of this rare lymphoproliferative disorder.