The present study demonstrates that morphine- and codeine-like molecul
es are present in Schistosoma mansoni following HPLC separation and id
entification with. an appropriate commercially available antibody. Fur
thermore, the endogenous material, corresponding to morphine, mimics a
uthentic morphine in Its ability to induce immunocyte rounding and imm
obility, an action that is naloxone sensitive. The codeine-like materi
al is not found at high concentrations compared to the morphine-like m
aterial, indicating, as in mammals and Mytilus edulis, the potential r
apid conversion of codeine to morphine. Coincubation with human leukoc
ytes increases the endogenous level of this material in adult worms, i
ndicating the presence of a positive feedback loop. Last, EDTA, a chel
ator of divalent cations, has a strong stimulating effect in the synth
esis of morphine-like material by the worm as noted by higher levels o
f this material in its presence. Taken together, the results suggest t
hat this parasite may utilize this immune downregulating molecule in i
ts effort to escape host immunosurveillance as well as in inhibiting a
n immune response directed against itself. (C) 1995 Academic Press, In
c.