ALTERNATIVE PATHWAY OF COMPLEMENT ACTIVATION IN FULL TERM AND PREMATURE-INFANTS

Classical and alternative pathway complement levels were measured in the cord blood sera of 60 newly born infants, with weights ranging from 1200-4165 g. The impact of maternal illness and infant illness on the complement levels was also evaluated. The mean values for CH50, C3, C4, PH50, factor B, and properdin were all significantly less than normal adult levels (P < 0.0001). All the above determinations were significantly correlated with one another except for the relationship between properdin and factor B. CH50, PH50, C4, and properdin levels were significantly correlated with birth weight although there was much residual scatter. Neither maternal illness nor mild to moderate illness in the newborn altered the birth weight-complement relationships. Severe infant illness did significantly alter the relationship between birth weight and complement. However, the impact of this variable on the birth weight-complement relationships was not consistent among the various components. These inconsistencies and the small sample size preclude drawing any strong conclusions about severe illness and complement levels. The alternative pathway activation sequence appears to be deficient to the same degree as the classical pathway activation sequence. This suggests that the entire serum complement system develops as a single unit. Severe illness in very low birth weight babies may be associated with abnormalities in serum complement levels greater than would be expected from the low birth weight alone.