A T-lymphocyte-derived factor that enhances IgG-dependent release of leukotriene B4 (LTB4) from human neutrophils.

We describe a human blood mononuclear cell (MNC)-derived leukotriene release enhancing factor (LREF) which significantly increased IgG-dependent leukotriene B4 (LTB4) generation by neutrophils. MNCs incubated with phytohaemagglutinin (PHA) or anti-CD3 monoclonal antibody and PHA-stimulated ER+ lymphocytes produced a 150-350% increase in LTB4 generation from IgG-stimulated neutrophils. With PHA, maximal activity was observed 48 hr after culture in serum-free medium. LREF was relatively stable when exposed to low pH (pH 2) or heat (56 degrees, 60 min). Following progressive purification by gel filtration (FPLC, Superose 12) and chromatofocusing (FPLC, Mono P) LREF was associated with proteins of molecular weight of 35-40 kD and a pI of 5.1-5.5. Partially purified LREF did not contain detectable amounts of interleukin 2 (IL-2) or interferon-gamma (IFN-gamma). Although high concentrations of recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF) (greater than 2 ng/ml) and recombinant tumour necrosis factor (rTNF) (greater than 100 U/ml) gave a slight (60%) enhancement of LTB4 generation, this was considerably less than that of partially purified LREF (350%). Our results suggest that human lymphocyte-derived LREF may play a role in the amplification of inflammatory reactions involving sensitized lymphocytes, neutrophils and lipid mediators.