10 - Mannose-binding lectin deficiency and susceptibility to infectious disease

Summary

INNATE IMMUNITY

The innate immune system is a set of cellular and humoral components which recognise the general features of microbes in order to clear these potentially damaging agents from the body. In contrast to the acquired immune system this does not require prior exposure to the infectious agent. The development of the innate immune system as a range of pattern recognition receptors (PRRs) designed to recognise pathogen-associated molecular patterns (PAMPs) is a response to the host's inability to store unique recognition molecules for every possible pathogen within the genome.

Mannose-binding lectin (MBL) is a part of the humoral innate immune system. It is a pattern-recognition molecule able to detect a wide range of microbial and altered self-targets and recruit a number of host immune effector systems to clear those targets (Turner, 1996). However, genetic deficiency of MBL is surprisingly common in most human populations (Turner and Hamvas, 2000).

The protein was first discovered through biochemical purification and the gene independently described after functional cloning by two research teams. The effects of human MBL deficiency were documented separately by these research efforts and led in due course to the discovery of the genetic polymorphisms that give rise to this deficiency. More recently, the details of disease susceptibilities and the mechanisms of these effects have been elucidated.