The fetus doesn't accept complements.
Cross
J C
JC
D000818:Animals; D005260:Female; D005333:Fetus / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011951:Receptors, Complement / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017463:Receptors, Complement 3b
C081470:Cr1l protein, mouse; D011951:Receptors, Complement; D017463:Receptors, Complement 3b