Immortalization of EBV-infected B cells is not influenced by exogenous signals acting on B cell proliferation. Effects of mutant EL-4 thymoma cells and transforming growth factor-beta.
We have recently developed a culture system in which 90% of B cells from human peripheral blood or spleen are induced to strongly proliferate and generate short-term clones of a mean of about 400 antibody-secreting cells. B cells are stimulated by mutant EL-4 thymoma cells in conjunction with T cell supernatant. In the present study, we first investigated whether the frequency of B cell immortalization by EBV would be higher in this system than in a conventional system by using PBMC as fillers. The results showed that the EBV-dependent cloning frequency (0.7%) was not increased compared with the system with the use of PBMC (2.1%). However, the short term proliferation of EBV-infected B cells was 20 times increased in the EL-4 system and EBV nuclear Ag-positive cells participated in this response. Recent reports showed that transforming growth factor-beta (TGF-beta) inhibited the growth of normal B cells, whereas the growth of EBV-immortalized (lymphoblastoid) cells was not inhibited. We have studied the effects of this cytokine in the EL-4 system. TGF-beta (200 pg/ml) was found to inhibit the proliferative response of normal B cells by greater than 95% and the short term response of EBV-infected B cells by 78%. In contrast, the EBV-dependent long term cloning frequency, as well as the proportion of clones producing IgM, IgG, or IgA, was not influenced at all by TGF-beta. In conclusion, potent modulation of the early proliferative response of an EBV-infected B cell population by either stimulatory or inhibitory exogenous signals did not influence the number of cells that subsequently became immortalized.
Straub
C
C
Department of Medicine, Hôpital Cantonal, Geneva, Switzerland.
Zubler
R H
RH
D000956:Antigens, Viral / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology*; D002472:Cell Transformation, Viral / Q000187:drug effects*; D002474:Cell-Free System; D002999:Clone Cells / Q000276:immunology; D019309:Epstein-Barr Virus Nuclear Antigens; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007958:Leukocyte Count; D008213:Lymphocyte Activation / Q000187:drug effects*; D009154:Mutation; D013945:Thymoma / Q000235:genetics / Q000276:immunology*; D015291:Transforming Growth Factors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000956:Antigens, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; D015291:Transforming Growth Factors