Surfactant Protein D in Newborn Infants: Factors Influencing Surfactant Protein D Levels in Umbilical Cord Blood and Capillary Blood

Abstract

Surfactant protein D (SP-D) is a collectin that plays an important role in the innate immune system. The role of SP-D in the metabolism of surfactant is as yet quite unclear. The aims of this study were to establish normal values of SP-D in the umbilical cord blood and capillary blood of mature newborn infants and to assess the influence of perinatal conditions on these levels. A total of 458 infants were enrolled in the present study. Umbilical cord blood was drawn at the time of birth and capillary blood at age 4 to 10 d. The concentration of SP-D in umbilical cord blood and capillary blood was measured by enzyme-linked immunosorbent assay. The median concentration of SP-D in umbilical cord blood was 392.1 ng/mL and was found to be influenced by maternal smoking and labor. The median concentration of SP-D in capillary blood was 777.5 ng/mL and was found to be influenced by the mode of delivery, the highest levels being observed in infants born by cesarean section. It was concluded that SP-D concentrations in umbilical cord blood and capillary blood are highly variable and depend on several perinatal conditions. Further studies are needed to elucidate the effect of respiratory distress and infection on SP-D concentrations. Collectins are oligomeric molecules consisting of carbohydrate recognition domains attached to collagen-like regions (5). In humans, three well-studied collectins are known at present (6). These are MBL, which is a serum protein, SP-A, and SP-D. SP-A and SP-D are mainly produced in the epithelial cells of the lungs, but SP-D is also found in epithelial cells and secretory glands in the gastrointestinal tract and in other tissues (7). SP-D plays an important role in the innate immune defense by binding to specific carbohydrate and lipid structures on the surface of microorganisms: bacteria, viral particles, fungi, and protozoa (8 -11). This binding mediates effector mechanisms like aggregation, chemotaxis, mediation of phagocytosis, and permeabilization (12). Pulmonary infections in adults have been shown to cause significant changes in SP-D levels (13). Whether SP-D has a role in avoiding infections in newborn babies has to our knowledge not been investigated.Both structural and promoter variants are known for the MBL gene, and several alleles correlate with low values of MBL in serum and lead to an increased risk of infectious diseases in otherwise healthy children (14,15). Three polymorphisms have been identified in the coding sequence of human SP-D: codons corresponding to amino acid residue 11 (Met11Thr), residue 160 (Ala160Thr), and residue 270 (Ser270Thr) in the mature protein. Two clinical studies have associated the SP-D variants of amino acid 11 with disease. The SP-D allele coding for methionine 11 has been associated with severe respiratory syncytial virus infection in infants, whereas threonine 11 has been suggested to increase susceptibility to tuberculosis (16,17). However, the connection between structural genetic variance and serum SP-D has not been investigated. We have perfo...

Surfactant Protein D Levels in Umbilical Cord Blood and Capillary Blood of Premature Infants. The Influence of Perinatal Factors

“…We found markedly increased levels of SP-D in umbilical cord blood and capillary blood on the first day of life in infants that later developed sepsis independent of interval between birth and the diagnosis of septicemia. This finding is consistent with our data obtained in mature newborn infants (16). One could speculate that the high SP-D levels were due to an increased capillary leak leading to decreased levels of SP-D in the lungs.…”

“…Recently we have shown by immunohistochemical analysis that SP-D is synthesized in all villous and extravillous trophoblast sub-populations in the placenta (34). Consistent with this, we have demonstrated decreased SP-D levels in umbilical venous blood in mature infants of smoking mothers (16). However, in the present study the SP-D levels of infants from smoking mothers were only lower in capillary blood and not in umbilical venous cord blood.…”

“…The SP-D levels in umbilical cord blood from premature infants were twice as high as in mature infants, and did not decrease with gestational age as we previously described in mature infants for gestational age 36 -43 wk (16). These data suggest that the decrease in SP-D levels occurs late in pregnancy.…”

“…The levels of SP-A in cord blood has been found to predict RDS among prematurely born infants (15). We have demonstrated that levels of SP-D in cord blood and capillary blood of mature newborn infants depend on several maternal and perinatal conditions (16) including labor, mode of delivery and maternal smoking. In this study we report, to our knowledge for the first time, cord blood and capillary blood levels of SP-D in premature infants and their influence on respiratory distress syndrome and susceptibility to neonatal infections.…”

“…We have recently demonstrated that SP-D levels in cord blood and capillary blood of mature infants are influenced by mode of delivery, labor and maternal smoking (16). In this study we have determined the levels of SP-D in prematurely born infants.…”