PLACENTAL MONOCYTE FUNCTION
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Date
1996-05
Type of Work
Department
Hood College Biology
Program
Biomedical and Environmental Science
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Abstract
Modern technological advances have allowed investigators to learn a great deal about
the feto-maternal interface. However, much is still not understood about the immunological
basis of a successful pregnancy. Even though a few fetal erythrocytes and leukocytes escape
into maternal circulation and minor breaks in the placental barrier allow cells to escape in both
directions, cells of the embryo normally do not come into direct contact with maternal blood.
Maternal blood flows into the placenta filling the intervillous spaces and circulates around the
fetal villous tree. The focus of this study was to investigate maternal monocyte function at the
time of labor and delivery, particularly the ability to activate monocytes to phagocytize
bacteria. Maternal peripheral blood was collected during labor and again within 24 hours of
delivery. Placentas were harvested and maternal blood from the intervillous spaces was
collected within 6 hours of delivery. Monocytes were separated from all whole blood test
specimens as well as nonpregnant female control subjects by density gradient centrifugation
and adhesion of monocytes to plastic. The monocytes were then incubated in culture medium
with an equal ratio of Listeria monocytogenes bacilli. Monocytes were treated with
recombinant human gamma-interferon as an activation signal. No significant difference in the
number of viable phagocytized bacteria between interferon-treated and untreated monocytes
was observed in any of the test specimens. There was a small, yet statistically relevant,
increase in the interferon-treated control cells after 20 hours incubation. The inability of
interferon alone to activate monocytes from the placenta and peripheral circulation of women
during delivery may be due to the need of a second cooperative signal, perhaps TNF-a or
GM-CSF. An alternative is that due to the nature of the processes of labor and delivery, there
were present both locally in the placenta and globally in the general circulation various
mediators that have the ability to initiate labor and modulate monocyte activity. Further study
is warranted to test the ability to activate these monocytes. The production of reactive nitrogen
and oxygen intermediates could be assayed as well as the effect of various uterotonins on the
activation process. If the immunological processes preventing the rejection of a genetically
dissimilar fetus were understood, progress could be made in transplantation science as well as
the treatment of infertility and novel approaches to birth control.