Dextran sulfate-mediated enhancement of mitogen-induced B-cell proliferation

We have studied lipopolysaccharide (LPS)-induced proliferation of rat lymphocytes and have found that a serum-free tissue culture medium supports significant cell division. When the compound dextran sulfate (DxS), which itself is not mitogenic, is added to LPS-stimulated cultures, significant augmentation of proliferation results. DxS will significantly enhance anti-immunoglobulin-induced proliferation as well. An intact T-cell compartment is not required for DxS-mediated enhancement of LPS-induced cell division, in that lymphocytes derived from athymic rats proliferate and respond to the influence of DxS to the same degree as euthymic derived lymphocytes. A "DxS-free" supernatant from DxS-stimulated spleen cell cultures is able to substitute for DxS in all stimulatory activity. This supernatant possesses interleukin 1 (IL-1) activity. However, purified recombinant IL-1 does not cause enhanced proliferation when added to LPS-stimulated cultures as is seen with DxS or the "DxS-free" supernatant.