Effects of phorbol esters and cytokines (interleukin-2,-4, and -6) on the proliferation and surface phenotype of Epstein-Barr virus immortalised human B lymphocytes.

Epstein-Barr virus (EBV)-induced in vitro infection of peripheral blood mononuclear cells (PBMCs) leads to a polyclonal proliferation and immortalisation of B lymphocytes. In the present study we determined the effects of three different cytokines, interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-6 (IL-6), and the tumour promoting phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on EBV-immortalised B lymphocytes. These factors have known activities on normal B cells. IL-4 and IL-6 increased significantly EBV-B cell proliferation after 3 and 5 days of culture, where IL-2 had no effect. The effect of IL-4 and IL-6 on EBV-B cells was abolished after pre-incubation with anti-IL-4 and anti-IL-6 neutralising antisera, respectively. TPA induced a dose dependent inhibition of proliferation both in serum free and 10% fetal calf serum (FCS) supplemented culture medium. Combinations of TPA and interleukins did not restore lymphoblastoid cell proliferation to background levels. All possible combinations of the three cytokines showed no synergistic or antagonistic effect on proliferation. TPA induced significant phenotypic changes of EBV immortalised B lymphocytes, by increasing IL-2 receptor (IL-2R) expression and decreasing CD20 and CD23 antigen expression. Other B cell differentiation antigens; HLA-DR, CD19, and transferrin receptor (CD71), did not demonstrate significant changes. A dose dependent inhibition of CD21 and increase in CD22 expression was observed in 2 out of 3 lymphoblastoid cell lines tested.