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The problems of immunologic adaptation during the transitional period from intra- to extrauterine life are responsible for the physiologic immaturity of the immune function in newborn infants. In preterm neonates the immunodeficiency is more severe and prolonged and is associated with a higher incidence of infections and sepsis. Furthermore, due to immaturity of the hematologic system, anemia, thrombocytopenia, and neutropenia are frequently observed in very low birth weight infants. The dysregulation of cytokine and hematopoietic growth factor synthesis is an important contributory factor to the complex deficiency of immunologic and hematologic function in the neonate and may explain the reduced incidence of acute graft-versus-host disease observed after cord blood transplantation in children. Human milk is a rich source of most of the cytokines that are reduced in the neonate. Granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and erythropoietin are currently under evaluation in newborn infants with septic neutropenia or anemia of prematurity.

Some studies have suggested that decreased seroconversion rates might be found in premature infants with low birthweight (< 2000g) following administration of hepatitis B vaccine at birth. The aim of the present investigation was to evaluate possible differences in seropositive rates between full-term and preterm infants after primary vaccination, in particular when gestational age or birthweight is very low. Two-thousand and nine neonates born to HBsAg-negative mothers were vaccinated with 10 microg of recombinant hepatitis B virus (HBV) vaccine, from May 1991 to October 1994. Children with infections, congenital malformations or serious illnesses were excluded. HBV vaccine was administered intramuscularly, on the fourth day of life and again at 1 and 6 months of age. A 1-ml blood sample was drawn from each infant 1 month after the third vaccine dose for determination of the level of anti-HBs antibody. The response to HBV vaccination was evaluated in 241 preterm (gestational age <38 weeks) infants and 1727 term neonates. No statistical difference was observed in the distribution of anti-HBs antibody level, either between preterm infants (<38 weeks) and newborns of normal gestational age, or between low birthweight (<2500 g) and normal weight infants. The results suggest that preterm and low birthweight infants (<2500g) respond to HBV vaccine in the same measure as normal-term infants.

Unlabelled: We measured serum granulocyte colony stimulating factor (GCSF) concentration and absolute neutrophil count in four groups of infants: (1) 15 healthy term newborn infants; (2) 21 healthy preterm newborn infants, with mean (SD) birth weight 1583 (533) g, and gestational age 32.0 (3.8) weeks; (3) 5 infected newborn infants; (4) 22 6-month-old control infants. Median (range) serum GCSF concentration was 132.2 (41.5-176.0) pg/ml in term infants, 51.5 (1.8-175.7) pg/ml in preterm infants and 138.9 (54.1-449.8) pg/ml in 6-month-old control infants, with a significant reduction in preterm infants, as compared to term and control infants. GCSF levels were significantly higher in the infected infants, as compared to healthy neonates., Conclusion: A significant positive relationship was found in term and preterm infants between serum GCSF concentration and gestational age or birth weight. No relationship was found between serum GCSF concentration and neutrophil count. The low GCSF baseline levels may contribute to the increased incidence and severity of infection in preterm infants.

Kidney volume in relation to gestational age, birthweight, and height was determined in 121 infants, 58 females and 63 males, with gestational ages from 23 to 43 weeks (mean, 33.3) and birthweight from 430 to 4600 gm (mean, 1982 gm). The kidney volume was measured using a real-time linear computed ultrasound scanner, with a 5 MHz transducer. The renal volume was calculated from outer kidney diameters using the volume formula for an ellipsoid. In the infants studied, mean volume of the right kidney was 6.0 ml (range, 1.4 to 13.8 ml), and of the left kidney 6.6 ml (range 1.5, to 15.6 ml), with no significant difference. A highly significant correlation was found between the volume of both kidneys and either gestational age, or birthweight, or height, with r values ranging from 0.81 to 0.92. The best correlation was observed with birthweight. No significant difference was found between males and females.

Cystic periventricular Leukomalacia (CPVL), a hypoxic-ischemic lesion of the neonatal brain, which can now be diagnosed in life thanks to ultrasound brain scanning, is considered to be one of the main causes of cerebral palsy (CP), especially in preterm infants. The purpose of our study was to verify this assumption in a population of 337 of gestational age greater than or equal to 32 weeks. The frequency of CPVL proved to be 5.4% for lesions with a diameter of greater than or equal to 3 mm or 9.3% including those of smaller diameter. The development of CPVL infants was favorable in 29% and adverse in 71% of cases. In the latter cases neuromotor sequelae (CP in 62.5% and motor retardation in 8.5%) were accompanied by various other neuropsychic deficits. Prognosis depends on the site and size of the cysts, being harsher for posterior lesions and those exceeding 1 cm in diameter.

Immunodeficiency, particularly antibody deficiency, is a crucial contributory factor to the increased susceptibility to infections in preterm infants. Availability of the recent preparation of intravenous immunoglobulin (ivIgG) led several authors to evaluate the safety and effectiveness of ivIgG for prophylaxis of infection in preterm infants. The results of these studies, although controversial, have pointed out two common findings: (1) ivIgG prophylaxis seems to be effective only in the very preterm infants, with mean birth weight below about 1,300 g: (2) ivIgG seems to be well tolerated by newborn infants.

The present longitudinal study of 40 healthy term infants and 20 preterm infants shows that neutrophil bactericidal activity against Staphylococcus aureus and Streptococcus faecalis is transiently but significantly impaired in term infants during the 1st week of life. The deficiency is more severe and prolonged in preterm infants, and may contribute to the neonate's increased susceptibility to infections.

Complement-dependent serum bactericidal activity for E. coli K12 was assessed in 12 term infants and in 16 preterm infants. In both groups of newborns, at birth, bactericidal reaction by the classical pathway of complement activation was impaired with respect to normal controls at less than 0.001 level of significance (as estimated by Student's t-test). The serum bactericidal reaction by the alternative pathway of complement activation was significantly impaired only in preterm newborns, being normal in term infants. At a time corresponding to 40 weeks' gestational age also in preterm newborns alternative pathway mediated bactericidal activity for E. coli K12 was found normal. Classical pathway mediated bactericidal activity became normal only at an age corresponding to 52 weeks' gestational age.

In 20 healthy premature infants, 10 of whom were administered a total dose of 120 mg/kg vitamin E intramuscularly during the first 13 days after birth, polymorphonuclear leukocyte (PMN) bactericidal activity, frequency and index of phagocytosis, NBT reduction, random movement, chemotaxis and metabolic activity were evaluated within the first 48 hours and again at 5, 14 and 30 days of age. PMN function was also assessed in 30 adult controls. In the treated and untreated infants no differences were found in PMN function before treatment with vitamin E; however phagocytosis, bactericidal activity and chemotaxis were significantly lower than in the adult controls. At 5 days of age, in the untreated infants both index and frequency of phagocytosis remained low but in the treated groups increased significantly. At 14 and 30 days phagocytosis was normal in both treated and untreated infants. No differences were found in the bactericidal activity, NBT reduction, random movement, chemotaxis or metabolic activity of the treated and untreated infants at the ages studied. This preliminary report suggests that vitamin E may be used in premature newborns for accelerating normalization of phagocytic function in the neonatal period.

Complement 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 tH50, 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 CH50, 38.8 HU/ml +/- 13; AP tH50, 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 less than 0.001 in all cases). All complement parameters were mainly correlated with gestational age; CH50 values of the classical and alternative pathways were also highly correlated with each other (r = 0.64; P less than 0.001). Low birth weight infants, especially preterm infants, have an important defect of complement activity. Complement factors increase gradually during gestation and intrauterine growth retardation does not affect complement development. Classical and alternative complement pathway activities have a similar development pattern.

Kidney length was evaluated by ultrasound in 132 healthy neonates with gestational ages from 27 to 42 weeks and birth weights from 790 to 4200 g. A highly significant correlation was found between the length of the kidneys and gestational age or birth weight.