Post-neonatal drop in alveolar SP-A expression: biological significance for increased vulnerability to SIDS?
BACKGROUND
Surfactant protein A (SP-A) is synthesized in the lung and is a part of the innate immune system. The aim of this study was to evaluate the expression of SP-A in lung tissue from fetuses, infants, children and adults with special regard to sudden infant death syndrome (SIDS).


METHODS
A total of 160 cases were studied; 19 fetuses and neonates, 59 SIDS and 49 explained infant deaths below 1 year of age, 19 toddlers and 14 adults. Immunohistochemical detection of SP-A using monoclonal antibodies was performed by microscopy of lung tissue specimens collected at autopsy. A scoring system was developed enabling semi-quantitative estimation of staining intensity and distribution.


RESULTS
SP-A was detected in the terminal bronchioles and alveolar spaces of fetuses >35 weeks gestation. The intra-alveolar SP-A expression increased in the perinatal period followed by a marked drop in infants aged between 1 week and 5 months. Infants aged >5 months had abundant SP-A expression corresponding to older children and adults. There was no difference in the age distribution between cases of SIDS and explained deaths.


CONCLUSIONS
The apparent drop in SP-A expression takes place in the first months after birth, corresponding with the classical age peak of SIDS. We therefore hypothesize that low expression of SP-A may be related in some as-yet undetermined way to the increased risk of SIDS at that age.
Stray-Pedersen
Arne
A
Institute of Forensic Medicine, University of Oslo, Rikshospitalet, Oslo, Norway. arne.stray-pedersen@labmed.uio.no
Vege
Ashild
A
Stray-Pedersen
Asbjorg
A
Holmskov
Uffe
U
Rognum
Torleiv Ole
TO
D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000911:Antibodies, Monoclonal; D001344:Autopsy; D015415:Biomarkers / Q000032:analysis; D002675:Child, Preschool; D015536:Down-Regulation; D005260:Female; D005313:Fetal Death; D005333:Fetus / Q000737:chemistry*; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009664:Norway / Q000453:epidemiology; D015588:Observer Variation; D011650:Pulmonary Alveoli / Q000737:chemistry*; D037662:Pulmonary Surfactant-Associated Protein A / Q000032:analysis*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013398:Sudden Infant Death / Q000209:etiology*
D000911:Antibodies, Monoclonal; D015415:Biomarkers; D037662:Pulmonary Surfactant-Associated Protein A