No abstract

In this study, acidic arabinogalactan, a highly purified polysaccharide from plant cell cultures of Echinacea purpurea, with a molecular weight of 75,000, was effective in activating macrophages to cytotoxicity against tumor cells and micro-organisms (Leishmania enriettii). Furthermore, this polysaccharide induced macrophages to produce tumor necrosis factor (TNF-alpha), interleukin-1 (IL-1), and interferon-beta 2. Arabinogalactan did not activate B cells and did not induce T cells to produce interleukin-2, interferon-beta 2, or interferon-gamma, but it did induce a slight increase in T-cell proliferation. When injected ip, this agent stimulated macrophages, a finding that may have therapeutic implications in the defense against tumors and infectious diseases.

Priming of macrophages from both murine and human sources by recombinant immune interferons from Escherichia coli (r-IFN-gamma s) and activation by lipopolysaccharide (LPS) resulted in the production of tumor necrosis factor (TNF). r-IFN-gamma alone did not induce TNF production by macrophages; for this to occur, the second signal provided by small amounts (nanograms) of LPS was required. The small amounts of LPS alone were insufficient to activate the macrophages for TNF production. Priming by r-IFN-gamma was not necessary when larger amounts of LPS were employed, although an enhancement of yield resulted. Priming could also be demonstrated in vivo. Inoculation of r-IFN-gamma into mice resulted in increased yields of TNF following LPS challenge 12 hours later.

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