Characterization and growth factor requirements of SJL lymphomas. I. Development of a B cell growth factor-dependent in vitro cell line, cRCS-X.

Reticulum cell sarcomas (RCS) of SJL mice are completely dependent on host cells for their growth and therefore fail to grow in vitro. RCS cells induce marked proliferation in SJL Ly-1+2- T cells accompanied by lymphokine production. In an attempt to fully understand the host-tumor cell interaction, an RCS cell line, cRCS-X, was established in vitro from a transplantable tumor by the addition, every 3 wk, of gamma-irradiated syngeneic lymph node (LN) cells to the culture. cRCS-X maintains all of the characteristics of the parent tumor, RCS-X, including cell surface phenotype (Ks and I-As positive, Ds negative and B cell marker 14.8 positive), ability to stimulate host T cells, and ability to grow in nonirradiated but not in gamma-irradiated SJL mice. The growth factor requirements of cRCS-X were examined. It was found that human BCGF can replace gamma-irradiated LN cells in the maintenance of long term in vitro growth of cRCS-X. cRCS-X cells respond to human B cell growth factor (BCGF) or to recombinant murine interleukin (IL)-5 in a short term proliferation assay [( 3H]thymidine incorporation) in a dose-dependent manner in the presence and absence of fetal calf serum. BCGF also promotes colony formation in soft agar by cRCS-X cells. Although both IL-1 and interferon-gamma can synergize with BCGF in the induction of cRCS-X proliferation, these lymphokines, as well as IL-2, IL-3, granulocyte-macrophage colony-stimulating factor, and IL-4 have no effect on cRCS-X growth when added alone. In addition, it was shown that SJL LN cells produce both IL-4 and BCGF II activities as assayed on murine B cells, after stimulation with gamma-irradiated cRCS-X cells. In light of these results it is postulated that IL-5, [corrected] produced by syngeneic T cells [corrected] after stimulation with RCS, is essential for RCS growth, both in vitro and in vivo.