Histologic distribution and biochemical properties of alpha 1-microglobulin in human placenta.
OBJECTIVE
The embryo is protected from immunologic rejection by the mother, possibly accomplished by immunosuppressive molecules located in the placenta. We investigated the distribution and biochemical properties in placenta of the immunosuppressive plasma protein alpha 1-microglobulin.


METHODS
Placental alpha 1-microglobulin was investigated by immunohistochemistry and, after extraction, by electrophoresis, immunoblotting and radioimmunoassay.


RESULTS
alpha 1-Microglobulin staining was observed in the intervillous fibrin and in syncytiotrophoblasts, especially at sites with syncytial injury. Strongly stained single cells in the intervillous spaces and variably stained intravillous histiocytes were noted. Solubilization of the placenta-matrix fraction and placenta membrane fraction released predominantly the free form of alpha 1-microglobulin, but, additionally, an apparently truncated form from the placenta-membrane fraction. The soluble fraction of placenta contained two novel alpha 1-microglobulin complexes.


CONCLUSIONS
The biochemical analysis indicates the presence in placenta of alpha 1-microglobulin forms not found in blood. The histochemical analysis supports the possibility that alpha 1-microglobulin may function as a local immunoregulator in the placenta.
Berggård
T
T
Department of Cell and Molecular Biology, Lund University, Sweden.
Enghild
J J
JJ
Badve
S
S
Salafia
C M
CM
Lögdberg
L
L
Akerström
B
B
D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D011863:Radioimmunoassay; D001613:beta 2-Microglobulin / Q000032:analysis*
D001613:beta 2-Microglobulin