Activity of classical and alternative pathways of complement in preterm and small for gestational age infants

mplement activity was compared in 50 low birth weight infants divided into appropriate and small for gestational age groups; the influence of birth weight and gestational age on complement development was also investigated. CH50 and kinetics (tH50) of both classical and alternative pathway activity of complement, C3, and Factor B levels were significantly higher in small for gestational age infants (classical pathway CH50, 630 HU/ml ± 184 SD; CP tHjo, 77 min ± 47; aternative pathway CH50, 44.8 HU/ml ±11.3; AP tH50, 56 min ± 43; C3, 73.98 mg/dl ± 12.68; and Factor B, 13.17 mg/dl ± 3.67) than in weight-matched appropriate for gestational age infants (CP CH50, 523 HU/ml ± 152; CP tH50, 105 min ± 49; AP CH5o, 38.8 HU/ml ± 13; AP tHs50, 90 min ± 53; C3, 58.14 mg/dl + 9.43; and Factor B, 9.32 mg/dl ± 1.73). Complement values were lower in low birth weight infants than in adult controls (P