Reticulum cell sarcomas of SJL mice have rearranged immunoglobulin heavy and light chain genes.

The immunoglobulin (Ig) heavy (H) and light (L) chain gene rearrangements of the high incidence SJL lymphomas (reticulum cell sarcoma, RCS) have been analyzed. Both primary and transplanted RCS show rearrangements of H and kappa L chains, demonstrating that these tumors are of B cell origin. These data are consistent with previous results indicating that these tumors are a mouse model for follicular lymphoma. A long-term transplanted line and the in vitro line derived from it, cRCS-X, have a single rearranged JH-C gamma 2a fragment and one rearranged C alpha gene fragment which does not hybridize with a probe for the JH gene segments. These cell lines also have two rearranged J kappa-C kappa fragments. Primary tumors and early passages are more heterogeneous with respect to Ig gene rearrangements, possibly because more than one B cell clone is present. Although no synthesis of IgG2a, or of any Ig, could be detected by the in vitro cRCS-X cells, these cells contain abundant poly(A)+ RNA that hybridize with gamma 2a and kappa probes as well as lesser amounts of alpha and epsilon RNA. None of these H chain RNA hybridized with probes for the JH gene segments. The epsilon and alpha RNA are the same size as transcripts of germ-line CH genes which have been identified in other systems. However, the gamma 2a RNA are smaller than previously described germ-line C gamma 2a RNA and appear to be transcribed from aberrantly rearranged JH-C gamma 2a genes.

Characterization and growth factor requirements of SJL lymphomas. II. Interleukin 5 dependence of the in vitro cell line, cRCS-X, and influence of other cytokines.

Follicular B cell lymphomas of SJL mice [reticulum cell sarcoma (RCS)] are dependent on syngeneic Ly-1+,2- T cells for their growth. These T cells produce a number of lymphokines in response to stimulation with gamma-irradiated RCS cells including interleukin (IL) 2, interferon-gamma (IFN-gamma), IL4 and IL5, some of which may be required for growth of the tumor. Previous studies have shown that an RCS cell line, cRCS-X, can be maintained in vitro indefinitely, if the cultures are supplemented with gamma-irradiated lymph node (LN) cells or with a preparation of human B cell growth factor (BCGF). In the present studies, the growth requirements of this cell line were analyzed in more detail in short-term assays of both [3H]thymidine incorporation and colony formation in agarose. Recombinant murine IL5 cause dose-dependent proliferation of cRCS-X cells similar to that induced with BCGF. The level of colony formation by cRCS-X cells induced by optimal concentrations of BCGF was not increased further by the addition of IL5, suggesting that the two factors act via a common mechanism. IL1 and IFN-gamma each enhanced cRCS-X proliferation induced by BCGF or IL5 in both assays. The effects of IL1 plus BCGF, IFN-gamma plus BCGF, and IL1 plus IL5 were clearly synergistic. Preincubation of cRCS-X cells with IL1 enhanced their ability to proliferate in response to BCGF or IL5 in [3H]thymidine incorporation assays, but the reverse sequence of cytokine addition showed no effect of IL1. No such effect was seen with IFN-gamma. Indeed, IL1 and IFN-gamma appeared to affect BCGF-induced cRCS-X growth by different mechanisms and their combined effects were greater than that of IL1 or IFN-gamma added separately. None of the other cytokines studied, including IL2, IL3, IL4, IL6, tumor necrosis factor-alpha, granulocyte monocyte-colony-stimulating factor or transforming growth factor-beta, had any detectable effect on cRCS-X cells, either alone or in combination with BCGF or IL5. Like IL5, SJL gamma-irradiated LN cells induced cRCS-X colony-forming units (CFU) in a dose-dependent manner. IL1, or the combination of IL1 plus IFN-gamma, clearly synergized with LN cells in the induction of cRCS-X CFU, suggesting that LN cells contribute IL5. The level of CFU induced by an optimal dose of BCGF was enhanced further in the presence of LN cells and IL1.(ABSTRACT TRUNCATED AT 400 WORDS)

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.