Schistosomula of Schistosoma mansoni were incubated in
RPMI 1640 medium containing 10% fetal calf serum, 10%
human portal venous or 10% human peripheral venous sera in the
presence of bromodeoxyuridine (BrdU) in order to
measure differences in cell proliferation. The rates of cell proliferation
as expressed by BrdU labelling indices (BLI) were
determined as a function of time of incubation by immunohistochemistry
using monoclonal antibody to BrdU. Compared
to schistosomula cultured in the presence of RPMI plus 10% fetal calf
serum, BLIs were increased by 60% in the presence
of human portal, but not in peripheral serum. This stimulatory effect
was substantially reproduced by a fraction of portal
serum with a molecular weight range between 1 and 50 kDa. However,
in the presence of human peripheral venous serum,
either whole or fractionated, schistosomula showed no significant
difference compared to RPMI plus 10% fetal calf serum
alone. Furthermore, human portal serum fractions of molecular weight
greater than 50 kDa also revealed no significant
difference relative to control. The results indicate that portal
venous serum component(s) of a molecular weight range
higher than most simple nutrients can greatly stimulate the rate
of cell proliferation of Schistosoma mansoni schistosomula.