Some recent trends in studies of human lymphoid cells: B-cells, Epstein-Barr virus, and transformation.

In this brief review we will discuss some re cent trends in work on regulatory mechanisms involved in the selective expression of differentiated markers in human B-ceIllines as weIl as the types of controls involved in the expression and function of Epstein-Barrvirus (EBV) associated markers in human cells. A problem of special interest in this connection is the relation of the expression of EBV functions to the expression of "transformation". In man EBV is a lymphotropic herpesvirus (Epstein and Achong 1979). Its main target is the human B-Iymphocyte (Jondal and Klein 1973), though EBV may be able to infect other cell types, provided that the membrane barrier is surpassed. EBV is known to be the causative agent of infectious mononucleosis (IM) (He nie and Henle 1979) and is associated with the two completely different human malignancies: African Burkitt's lymphoma (BL), i.e. malignant proliferation of B-cells (Fialkow et al. 1970), and nasopharyngeal carcinoma (NPC), i.e. malignant proliferation of epithelial carcinoma cells (Klein 1979). In both of these cases, the presence of the EBV genome is demonstrated by the presence of EBV DNA as well as by the presence of EBV -specific antigens. The case of NPC in itself indicates that cell types other than B-Iymphocytes under the right conditions can be infected byEBV. In addition to in vitro transformed lymphoblastoid cell lines (LCL), a wide variety of B -celllines of BL origin are available; so far it has not been possible to grow celliines from NPC tumors. B. Lymphoid Cell Lines