A naturally-occurring lysophospholipid; induces transient increases in intracellular calcium in PC12 rat neuronal cells in a concentration-dependent manner, an effect which can be blocked by the LPA1 antagonist AM095; increases IL-2 production in CD1d-stimulated murine NKT cell hybridoma 2H4 cells at 100 ng/ml; induces production of IL-4, but not IFN-γ, in murine splenocytes at 100 ng/ml and in mouse serum at 1 μg per animal; levels increase in iBAT in mice following three-day cold exposure