The analysis of the complement activation product SC5 b-9 is applicable in neonates in spite of their profound C9 deficiency.
Native complement factors and complement activation products were measured in healthy neonates (n = 72) and in a group of infants with premature prolonged rupture of the membranes (PPROM) without sepsis (n = 10). Vitronectin concentration in normal cord blood was not correlated with gestational age, and the median value was 86.0% of adult values. This was markedly higher than other native complement factors studied (factor B: 35.9%, C4: 45.1%, C3: 56.2%). The concentration of C9 showed a positive correlation with gestational age and was very low, 10.8% of normal adult values in cord blood and 8.3% in the patients. Fifteen percent of the neonates had C9 levels lower than 2% of adult values. The complement activation products Bb and SC5 b-9 were significantly elevated in the patients (159% and 130% of control values, respectively), indicating alternative and terminal pathway activation. In contrast, C4 bc and C3 bc levels were not increased. The maximum amount of SC5 b-9 which could be generated in the neonatal sera by cobra venom factor was highly correlated with C9 concentration (rs = 0.86, p = 0.0001) The profound C9 deficiency found in neonates is correlated with gestational age, limits the capacity to form bacteriolytic C5 b-9 (m) and may predispose for severe invasive bacterial infection. The plasma level of SC5 b-9 under normal conditions was very low, only 0.3% (0.1%-3.0%) of the values obtained after CVF activation of the same samples. Therefore, we suggest that the analysis of SC5 b-9 is applicable also in neonates, in spite of their extremely low C9 levels.
Høgåsen
A K
AK
Department of Pediatrics, National Hospital, Oslo, Norway. tore.abrahamsen@rh.uio.no
Overlie
I
I
Hansen
T W
TW
Abrahamsen
T G
TG
Finne
P H
PH
Høgåsen
K
K
D016470:Bacteremia; D002097:C-Reactive Protein / Q000032:analysis; D003167:Complement Activation; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D003186:Complement C9 / Q000032:analysis; D011415:Complement Factor B / Q000032:analysis; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins / Q000032:analysis*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005322:Premature Rupture of Fetal Membranes; D005865:Gestational Age; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D007118:Immunoassay; D007231:Infant, Newborn; D007234:Infant, Premature; D007958:Leukocyte Count; D008137:Longitudinal Studies; D008297:Male; D011247:Pregnancy; D019096:Vitronectin / Q000097:blood
D003176:Complement C3; D003181:Complement C4; D003186:Complement C9; D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; C047610:SC5b-9 protein complex; D019096:Vitronectin; D003165:Complement System Proteins; D002097:C-Reactive Protein; D011415:Complement Factor B