Human Molecular Genetics Advance Access originally published online on September 14, 2007
Human Molecular Genetics 2007 16(24):3071-3080; doi:10.1093/hmg/ddm265
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Heterozygosity of mannose-binding lectin (MBL2) genotypes predicts advantage (heterosis) in relation to fatal outcome in intensive care patients
1 Department of Anaesthesiology and Intensive Care, Herlev,, 2 Department of Clinical Immunology, sect.7631,, 3 Intensive Care Unit 4131,, 4 Department of Clinical Microbiology, Herlev,, 5 Copenhagen Trial Unit, Copenhagen University Hospital, Rigshospitalet, Denmark and 6 Clinical Institute, Århus University, Denmark
* To whom correspondence should be addressed at: Department of Clinical Immunology, sect. 7631, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen O, Denmark. Tel: +45 35457631; Fax: +45 35398766; Email: garred{at}post5.tele.dk
Received June 22, 2007; Accepted August 25, 2007
Polymorphisms in the MBL2 gene, which affect the structure and influence on the serum concentration of mannose-binding lectin (MBL), are associated with inflammatory and infectious conditions. The importance of MBL2 polymorphisms on outcome in critical ill patients is unclear. Five hundred and thirty-two consecutive critically ill patients admitted to an intensive care unit (ICU) were included over a period of 18 months. Five hundred and thirty-three individuals served as controls. Vital status was obtained 15.5 months after the last patient was included. MBL2 polymorphisms were determined by a PCR-based assay. Homozygosity for MBL2 variant alleles (O/O) causing MBL structural defects was associated with the highest adjusted mortality rate followed by homozygosity for the normal MBL2 allele (A/A) encoding high MBL levels, whereas heterozygous A/O patients had the most favourable outcome (P = 0.015). MBL2 alleles were not associated with death in ICU (n = 166, P = 0.7), but the association appeared soon after discharge from ICU (n = 366): hazard ratio (HR) for O/O using A/A as reference was 1.33 (95% CI: 0.8–2.2) and for A/O it was 0.62 (95% CI: 0.4–0.8) respectively (P = 0.0045) at completion. No difference in MBL2 frequency was observed between patients and controls at baseline, and between patients classified as having sepsis or not. However, patients with the MBL2 O/O genotype had an increased frequency of Gram-positive bacterial infection (P = 0.01). Heterozygosity for MBL2 alleles confers a protective effect whereas homozygosity is associated with the worst outcome soon after discharge from ICU. This may be an example of heterosis.