Epstein-Barr Virus Transformation Induces B Lymphocytes

Interleukin 10 (I1.10) is a pleiotropic factor that enhances proliferation of activated human B lymphocytes and induces them to secrete high amounts of immunoglobulins. Here we show that several human B cell lines were able to constitutively secrete human (h)Ibl0. Whereas none of the pre-B nor the plasmocytic cell lines tested produced hi1-10, 25 of the 36 tested mature B cell lines (lymphoblastoid and Burkitt lymphoma cell lines) secreted hi1.10. Moreover, 24 of these 25 hI1-10-producing B cell lines contained the Epstein-Barr virus (EBV) genome, suggesting a relationship between hi1.10 production by human B cell lines and EBV expression. Accordingly, whereas polyclonal activation via triggering of surface immunoglobulins or CD40 antigen induced highly purified normal human B lymphocytes to produce only low (0.3-0.4 ng/ml) but significant amounts of hIbl0, EBV infection induced them to secrete high amounts of hi1.10 (4-9 ng/ml). Furthermore, addition of exogenous hIbl0, simultaneously to EBV infection, potentiated cell proliferation, whereas a blocking anti-Ibl0 antiserum inhibited it. Thus, hi1.10 produced by infected human B lymphocytes appears to be involved in the mechanisms of EBV-induced B cell proliferation.