The Lectin Pathway of Complement and Biocompatibility

Abstract

In modern health technologies the use of biomaterials in the form of stents, haemodialysis tubes, artificial implants, bypass circuits etc. is rapidly expanding. The exposure of synthetic, foreign surfaces to the blood and tissue of the host, calls for strict biocompatibility in respect to contact activation, the coagulation system and the complement system. The complement system is an important part of the initial immune response and consists of fluid phase molecules in the blood stream. Three different activation pathways can initiate the complement system, the lectin, the classical and the alternative pathway, all converging in an amplification loop of the cascade system and downstream reactions. Thus, when exposed to foreign substances complement components will be activated and lead to a powerful inflammatory response. Biosurface induced complement activation is a recognised issue that has been broadly documented. However, the specific role of lectin pathway and the pattern recognition molecules initiating the pathway has only been transiently investigated. Here we review the current data on the field.

The Complement System in Dialysis: A Forgotten Story?

“…A genetic deficiency in ficolin-2 has not been reported to date, highlighting the essential function of this component within host defense. In conformity, ficolin-2 has been shown to be involved in the elimination of numerous pathogens ( 59 ).…”

“…In modern HD membranes, ficolin-2 seems to be an important mediator in HD-induced complement activation ( 28 , 33 ). Ficolin-2 is unfortunately a highly promiscuous molecule with numerous binding partners, several of which are acetylated compounds ( 59 ).…”

Complement Evasion Strategies of Viruses: An Overview

“…The three major pathways by which the complement system is activated are the CP, the LP, and the AP (Figure 1). The first two pathways are activated with the help of pattern recognition molecules (Degn and Thiel, 2013;Hein and Garred, 2015), while the last pathway is activated spontaneously and without any help from the pattern recognition molecules (Pangburn, 1983). Intriguingly, viruses are known to be recognized by all the three pathways (Rattan et al, 2013).…”

CsMAP34, a teleost MAP with dual role: A promoter of MASP-assisted complement activation and a regulator of immune cell activity

“…The complement system is activated via three major pathways, of which the lectin pathway serves as the first line of defense against microbial intruders1. It is activated when mannan-binding lectin (MBL) or ficolins binds appropriate carbohydrate or acetylated patterns of microbes2.…”

“…C3b binds the C3 convertase to form C5 convertase, which cleaves C5 to C5a, a potent anaphylatoxin, and C5b6. C5b recruits C6, C7, C8, and C9 molecules to assemble the terminal membrane attack complex (MAC)1, which creates a hole or pore in the membrane that can kill or damage the pathogen or cell7.…”