Classical complement activation induced by pregnancy: implications for management of connective tissue diseases.
OBJECTIVE
To determine the effect of pregnancy on C4d concentrations and to assess whether C4d remains a useful disease activity marker in the management of connective tissue diseases during pregnancy.


METHODS
Plasma C3, C4, and C4d concentrations were measured in 83 women at various stages of normal pregnancy and compared with those in 80 non-pregnant controls.


RESULTS
C3 concentrations in the pregnant women were significantly raised (p = 0.0001) and the C4 concentrations were reduced (p = 0.0007), and accompanied by a significant increase in C4d (p = 0.0001). The C4d:C4 ratio was higher in the pregnant women (p = 0.0001).


CONCLUSIONS
Pregnancy induces activation of the classical complement pathway. C4d concentrations cannot be used to monitor disease activity in patients with connective tissue diseases during pregnancy.
Hopkinson
N D
ND
Department of Immunology, University Hospital, Queen's Medical Centre, Nottingham.
Powell
R J
RJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis*; D015935:Complement C4b; D003171:Complement Pathway, Classical / Q000502:physiology*; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008875:Middle Aged; D010446:Peptide Fragments / Q000032:analysis*; D011247:Pregnancy / Q000276:immunology*; D011248:Pregnancy Complications / Q000276:immunology*
D003176:Complement C3; D003181:Complement C4; D010446:Peptide Fragments; D015935:Complement C4b; C032261:complement C4d