A raf/myc virus immortalized macrophage cell line which supports the growth of B-cell and B-cell hybridomas

Using a combination of raf and myc oncogenes co-expressed by the recombinant retrovirus J-2 we have generated and characterized a cell line which very efficiently supports the growth of B-cells and B-cell hybridomas. Murine spleen cells were cultured under in vitro immunization conditions favoring the short term proliferation of splenic B lymphocytes and infected with J-2 virus. Screening of immortalized spleen cell pools for the capability to support long term B cell growth in vitro led to the selection of a clonal cell line termed alpha ChyJ2. The presence of macrophage specific features and surface markers suggest that alpha ChyJ2 belongs to the macrophage lineage. alpha ChyJ2 cells constitutively produce low levels of IL-1 like activity and high levels of IL-6. Expression of specific mRNAs as well as production of IL-1 alpha, IL-1 beta and IL-6 are inducible with LPS. Expression or production of other cytokines including IL-2, IL-3, IL-4, IL-5, TGF beta and GM-CSF could not be detected. As the biological effects of alpha ChyJ2 supernatant cannot be fully explained by the described pattern of cytokine production, participation of other, yet uncharacterized, factors is possible. Using alpha ChyJ2 as feeder cells for in vitro as well as in vivo immunizations increased the number of antibody secreting B-cell clones 2 to 15 fold, respectively.