RECENT RESULTS ON THE BIOLOGY OF HODGKIN AND REED-STERNBERG CELLS .1. BIOPSY MATERIAL

The most recent sophisticated investigations have provided new and revealing, but also contradictory and controversial information on the biological nature and the cellular origin of Hodgkin and Reed-Sternberg cells (H-RS). Immunophenotypic analyses have shown variable phenotypic antigen expression; but, on balance the data suggest a lymphoid cell expressing T- and/or B-cell-associated markers and certain activation antigens while lacking immunological features of monocytes-macrophages or other lineages. Molecular genetic studies have demonstrated heterogenous findings with respect to rearrangements of T-cell receptor and immunoglobulin genes. Only a small percentage of the cases has rearrangements; this might be due to the threshold of sensitivity of the method combined with the scarcity of the malignant cells. Epstein-Barr virus (EBV) genomes are clonally integrated in the H-RS cells of about half the cases. The significance of these findings-whether EBV is a causative agent or an epiphenomenon-remains to be elucidated. H-RS cells express mRNA and proteins of various cytokines and cytokine receptors implying a predominant role for cytokines in the pathophysiology of HD. The mononuclear and polynuclear H-RS cells are capable of DNA synthesis and nuclear division; the lack of cellular division leads to multinuclearity through the process of endomitosis. Mutations and expression of only a limited number of oncogenes have been tested thus far. Whether the bcl-2 oncogene is involved in HD remains a matter of debate. Aneuploidy and non-random chromosomal abnormalities are the results of cytogenetic analyses of H-RS cells. However, no chromosomal marker specific for HD has yet been found. Thus, while studies of EBV involvement, growth factor production, oncogene expression and chromosomal abnormalities contributed a fair amount of new data on the nature of H-RS cells, only immunophenotyping and genotyping provided some indication of the cellular derivation: an activated lymphoid cell that possibly expresses oncogenes, that probably is infected with EBV, that most likely produces cytokines, that certainly has multiple karyotypic abnormalities.