Presence of activated macrophages in a murine model of early embryo loss.
OBJECTIVE
Even though our knowledge of the phenomenon at play at the fetoplacental interface has greatly advanced during the past years, a complete understanding of the reasons why the developing embryo is not rejected by maternal immune effector cells remains largely unknown.


METHODS
We have used immunohistochemistry with the macrophage-specific markers F4/80 and MHC II to study the relationship between decidual infiltration and resorption in murine models of embryo loss between days 6 and 10 of gestation.


RESULTS
Analysis of day 8 CBA/J x DBA/2 pregnancies has revealed 2 distinct populations of embryos. The majority (69.4%) expressed low levels of F4/80+ cells, but a minority (30.6%) expressed much higher level of the macrophage marker. In FBA/J x BALB/c, most embryos (91.7%) expressed low numbers of F4/80+ cells. As earlier experiments established that products of activated macrophages (TNF-alpha and nitric oxide) were implicated in embryo loss in this model, the activation status of the F4/80+ macrophages was assessed through the cell surface expression of MHC II. Again, a similar association was established: 30.6% of the CBA/J x DBA/2 embryos were infiltrated by significantly more MHC II+ cells than the control CBA/J x BALB/c mating. Finally, when coordinate expression of F4/80, MHC II and CD11b was assessed, it was found that an embryo significantly infiltrated by cells bearing one of the 3 markers was also heavily infiltrated by cells bearing the 2 other markers.


CONCLUSIONS
This study has shown that the augmented infiltration of the deciduum with maternal macrophages is an early event which precedes spontaneous abortion of the early embryo.
Duclos
A J
AJ
Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada.
Haddad
E K
EK
Baines
M G
MG
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002452:Cell Count; D002465:Cell Movement / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D005313:Fetal Death / Q000276:immunology* / Q000473:pathology; D005865:Gestational Age; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D008262:Macrophage Activation; D008297:Male; D008431:Maternal-Fetal Exchange / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D011247:Pregnancy
D015415:Biomarkers; D000949:Histocompatibility Antigens Class II