Involvement of interleukin-10 (IL-10) and viral IL-6 in the spontaneous growth of Kaposi's sarcoma herpesvirus-associated infected primary effusion lymphoma cells

Primary effusion lymphoma (PEL) is a distinct type of lymphoma associated w ith Kaposi's sarcoma-associated herpesvirus (KSHV) infection. To determine the factors responsible for the unrestrained proliferation of PEL, we have studied the growth factor requirements of the PEL-derived BCBL-1 and BC-1 c ell lines. Both cell lines were found to be autocrine growth factor depende nt and to release human interleukin-6 (IL-6), viral IL-6 (vIL-6), and human IL-10 in the culture supernatant. To establish whether these cytokines con tribute to autocrine growth, neutralizing antibodies against human IL-6, vI L-6, human IL-10, and soluble IL-10 receptor were used. These experiments s howed that human IL-10 and, to a lesser degree, vIL-6 serve as autocrine gr owth factors for BCBL-1 and BC-1 cells. Thus, human IL-10 and vIL-6 are gro wth factors released and used by PEL cells for autonomous proliferation and may be critical to the development and progression of PEL.