[Acute respiratory tract infections and mannose-binding lectin insufficiency in small children].
BACKGROUND
According to hospital-based studies, increased susceptibility to certain infections is associated with genotypes that cause low serum levels of the protein mannose-binding lectin (MBL). However, the contribution of MBL insufficiency to the incidence of common childhood infections on a population basis is unknown. To investigate the effect of MBL insufficiency on the risk of acute respiratory infections (ARI) in unselected children, we performed a prospective population-based study of ARI in young children in Sisimiut, Greenland.


METHODS
An open cohort of children aged 0-2 years was formed in 1996, and followed up with weekly morbidity surveillance visits for a two-year period. Episodes of ARI were diagnosed on medical history and clinical examinations. MBL genotypes were determined from blood samples according to the presence of structural alleles and promoter alleles.


RESULTS
Altogether 294 children participated and 44 refused. Blood samples were taken from 252 participants. A 2.1-fold (95% confidence interval 1.4-3.1) increased risk of ARI was found in MBL-insufficient children compared with MBL-sufficient children (p < 0.001). The risk association was largely restricted to the period 6 to 17 months of age, whereas less or no effect could be shown in younger and older children.


CONCLUSIONS
These population-based data suggest that genetic factors such as MBL insufficiency play an important role in host defence, particularly during the vulnerable period of infancy between 6 and 17 months of age, when the adaptive immune system is immature.
Koch
Anders
A
Afdeling for epidemiologisk forskning, Statens Serum Institut, Artillerivej 5, DK-2300 København S. ako@ssi.dk
Melbye
Mads
M
Sørensen
Per
P
Homøe
Preben
P
Madsen
Hans O
HO
Mølbak
Kåre
K
Hansen
Christoffer Holst
CH
Andersen
Lasse Høgh
LH
Hahn
Gitte Weinkauff
GW
Garred
Peter
P
D000208:Acute Disease; D000483:Alleles; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000208:ethnology; D005838:Genotype; D006116:Greenland / Q000208:ethnology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D037601:Mannose-Binding Lectin / Q000172:deficiency* / Q000235:genetics / Q000276:immunology; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000097:blood / Q000235:genetics*; D012307:Risk Factors
D037601:Mannose-Binding Lectin