Expression of eosinophil-granule major basic protein messenger ribonucleic acid in placental X cells.
BACKGROUND
The human eosinophil-granule major basic protein (MBP) is a 13.8-kilodalton cationic polypeptide constituting the core of the eosinophil granule. MBP is cytotoxic to parasites and numerous mammalian cells and is a potent secretagogue for platelets, basophils, mast cells, and neutrophils. Concentrations of a molecule immunochemically similar to eosinophil granule MBP are present in maternal plasma, and MBP has been localized by immunofluorescence to placental X cells.


METHODS
To determine whether X cells produce MBP, the expression of MBP messenger RNA (mRNA) was investigated in placentas by Northern blot analyses and by in situ hybridization with 35S-labeled RNA probes.


RESULTS
Northern blot analyses of RNA from placental septa and villi showed the existence of a 1.0-kb RNA band that hybridized with the MBP anti-sense probe; no MBP mRNA was detected in whole blood of normal or pregnant women or in cord blood. Analyses of placentas by in situ hybridization showed MBP mRNA in X cells of placental septa and anchoring villi, but not in other cellular elements such as syncytiotrophoblasts, cytotrophoblasts, villous stromal cells, and fetal endothelial cells. RNase pretreatment abolished X-cell hybridization signals; treatment of sections with an excess of nonradiolabeled anti-sense RNA also blocked binding of the 35S-labeled anti-sense RNA probe. Additional evidence supporting the production of MBP by X cells was obtained using a combination of in situ hybridization and immunofluorescence, which showed colocalization of MBP and its mRNA.


CONCLUSIONS
The presence of MBP mRNA and MBP protein in placental X cells indicates that X cells synthesize this biologically active molecule.
Bonno
M
M
Department of Immunology, Mayo Clinic, Rochester, Minnesota.
Kephart
G M
GM
Carlson
C M
CM
Loegering
D A
DA
Vernof
K K
KK
Gleich
G J
GJ
D001798:Blood Proteins / Q000032:analysis*; D015152:Blotting, Northern; D047091:Eosinophil Granule Proteins; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D017403:In Situ Hybridization; D010920:Placenta / Q000737:chemistry* / Q000166:cytology; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis*; D012260:Ribonucleases
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D012333:RNA, Messenger; D012260:Ribonucleases