Mannose-Binding Lectin Deficiency
Pronunciation: MAN-ohs BY-ding LEK-tin
Also written as: MBL — Mannose-Binding Lectin
An innate immune defect in which low serum levels of mannose-binding lectin impair complement activation via the lectin pathway, predisposing children to recurrent bacterial infections.
Full Definition
Mannose-binding lectin (MBL) is a pattern-recognition molecule of the innate immune system that initiates the lectin pathway of complement activation upon binding to carbohydrate patterns on microbial surfaces. MBL deficiency, caused by single nucleotide polymorphisms in the MBL2 gene, results in reduced opsonisation and complement-mediated killing of encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus influenzae. It is considered a susceptibility factor rather than a classical primary immunodeficiency and frequently acts synergistically with other mild immune defects. The clinical significance of isolated MBL deficiency in otherwise healthy children remains debated. Editors should hyphenate 'mannose-binding' as a compound modifier before 'lectin' and use the abbreviation MBL consistently after first mention.
Usage
Usage note: Always hyphenate 'mannose-binding' as a compound adjective. MBL is acceptable on subsequent mention; do not confuse with 'MBL' used for 'marine biological laboratory' in non-clinical texts.
In Context
- "Mannose-binding lectin deficiency was identified as a contributing factor to the child's recurrent otitis media episodes." — Paediatric immunology journal article
- "The clinical report noted low MBL levels but emphasised that isolated mannose-binding lectin deficiency rarely warrants immunoglobulin replacement in isolation." — Case discussion summary