Akm. Hogasen et al., The analysis of the complement activation product SC5 b-9 is applicable inneonates in spite of their profound C9 deficiency, J PERIN MED, 28(1), 2000, pp. 39-48
Native complement factors and complement activation products were measured
in healthy neonates (n = 72) and in a group of infants with premature prolo
nged rupture of the membranes (PPROM) without sepsis (n 10). Vitronectin co
ncentration in normal cord blood was not correlated with gestational age, a
nd the median value was 86.0 % of adult values. This was markedly higher th
an other native complement factors studied (factor B: 35.9 %, C4: 45.1 %, C
3: 56.2 %). The concentration of C9 showed a positive correlation with gest
ational age and was very low, 10.8 % of normal adult values in cord blood a
nd 8.3 % in the patients. Fifteen percent of the neonates had C9 levels low
er than 2 % of adult values. The complement activation products Bb and SC5b
-9 were significantly elevated in the patients (159 % and 130 % of control
values, respectively), indicating alternative and terminal pathway activati
on. In contrast, C4 be and C3 he levels were not increased. The maximum amo
unt of SC5 b-9 which could be generated in the neonatal sera by cobra venom
factor was highly correlated with C9 concentration (r(s) = 0.86, p = 0.000
1) The profound C9 deficiency found in neonates is correlated with gestatio
nal age, limits the capacity to form bacteriolytic C5 b-9 (m) and may predi
spose 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 t
hat the analysis of SC5 b-9 is applicable also in neonates, in spite of the
ir extremely low C9 levels.