Mannose-binding lectin (MBL) plays a crucial part in activation of the lectin pathway of the complement system. Increased susceptibility to certain infections is associated with low serum levels of MBL due to MBL variant alleles, but the contribution of MBL insufficiency to incidence of common childhood infections is unknown. In the 14 March Journal of the American Medical Association Anders Koch and colleagues report evidence that MBL insufficiency increases the risk of acute respiratory tract infection (ARI) in children (JAMA 2001, 285:1316-1321).

Koch et al studied for two years a cohort of 252 children, 24 months or younger, from Sisimiut, Greenland. The authors assessed the risk of ARI from the clinical data and compared it with presence of structural and promoter MBL alleles determined from blood samples of the children. Relative risk of ARI was 2.08-fold higher in MBL-insufficient children (n=13) compared with MBL-sufficient children (...