Serum complement and immunoglobulin values in small-for-gestational-age infants

Abstract

THE COMPLEMENT SYSTEM plays an important role in the opsonization and lysis of organisms, neutrophil chemotaxis, and activation of vascular responses to infection. To our knowledge, no formal study of the activity of this component of the humoral immune system in the serum of small-for-gestational-age babies has been reported. In view of the possibility of increased infection rates in this group of neonates, 1 this aspect deserves attention. This study compares the activity of the classical and alternative complement pathways in the serum of SGA babies with controls who were of appropriate weight for gestational age. Specific complement components, immunoglobulins, and serum proteins are also compared. PATIENTS AND METHODS We studied 28 term newborn infants, of whom 17 were SGA and 11 AGA. Maternal infection, amnionitis, or prolonged rupture of membranes precluded entry into the study. Sick and congenitally abnormal infants were similarly excluded. In an attempt to exclude infants with chronic intrauterine infection, serum IgM was measured and, when possible, placental histology examined. Gestational age was determined by the Dubowitz method. On the basis of applicable growth standards/ the infants were classified above or below the tenth percentile for weight. Significant hypertension complicated nine of the 17 SGA pregnancies, and one mother was a grand multipara. The causes of growth retardation in the others were not established. Peripheral venipuncture was performed within 48 hours of birth (mean age 7 hours) and the blood allowed to clot at room temperature for 30 minutes. Aliquoted serum samples were stored at -80~ for up to three months. Informed consent for venipuncture was obtained. Classical pathway (CH50) titration. This was performed according to the method of Kabat and Mayer? A single volume of normal adult serum was aliquoted and frozen at -80~ Each batch analysis of patient's serum was done in parallel with this control and the values expressed