NEW CHARACTERIZATION OF INFECTIOUS-MONONUCLEOSIS AND A PHENOTYPIC COMPARISON WITH HODGKINS-DISEASE

Recent nucleic acid hybridization studies have implied that Reed-Stern berg/Hodgkin (RS/H) cells are infected with Epstein-Barr virus (EBV) b efore malignant transformation, and hence, that Hodgkin's disease coul d develop as a consequence of malignant transformation of an EBV-infec ted cell. This study is a detailed immunohistochemical and in situ hyb ridization characterization of the various lymphoid cells in nine case s of infectious mononucleosis (IM), the acute manifestation of EBV inf ection. The RS/H-like cells of IM were similar in most respects to the ir morphologically identical counterparts in Hodgkin's disease; they e xpressed the EBV-encoded protein LMP1, EBV EBER1 transcripts, and CD30 and rarely, if ever, expressed CD45/LCA or T cell markers. Dissimilar ities were limited to CD15 negativity and the absence of a collarette of T cells around the RS/H-like cells of IM compared with their Hodgki n's counterparts. Expression of the immortalizing bcl-2 oncoprotein wa s variable in the RS/H-like cells of IM, as has been demonstrated in t he RS/H cells of Hodgkin's disease by other investigators, An apoptosi s assay suggested that many apoptotic cells in IM were EBV-infected T cells, in keeping with the previous in vitro observation that IM-deriv ed T cells succumb to apoptosis. Additionally, the apoptosis assay sug gested that RS/H-like cells of IM can succumb to programmed cell death , reminiscent of the mummified RS/H cells seen in Hodgkin's disease. T he accumulation of evidence suggests that RS/H-like cells of IM are mo re similar to true RS/H cells than previously recognized.