Lectin Pathway

Group of proteins that recognize andbind to specific groups.✓ Homeostatic roles✓ PRRS for pathogen sugars (found onbacterial cell wall)

Triggered by the binding of soluble pattern-recognition molecules (lectins) to microbial carbohydrates (Mannose-bindinglectin, Ficolins)

Activate proteases that activatecomplement.

Innate pathway triggered simply by thepresence of bacterial PAMPs.

1. initiation

2. MBL-MASP Complex Formation

3. Activated MASPs

4. Cleavage of Complement Proteins

5. Amplification and Effector Functions

6. Regulations

Steps of Lectin Pathway

Initiation- one of the key recognition moleculesinvolved in this pathway is mannose-binding lectin(MBL), a pattern recognition receptor (PRR) presentin the bloodstream

mannose-binding lectin(MBL) ; pattern recognition receptor (PRR) ; bloodstream

Initiation- one of the key recognition moleculesinvolved in this pathway is — , a — presentin the —

MBL-MASP Complex Formation - MBL circulates inthe bloodstream in association with MBLassociated serine proteases (MASPs), primarilyMASP-1 and MASP-2

MBL-MASP Complex Formation - MBL circulates inthe bloodstream in association with MBLassociated serine proteases (MASPs), primarilyMASP-1 and MASP-2

MBL-MASP Complex Formation - MBL circulates inthe bloodstream in association with MBLassociated serine proteases (MASPs), primarilyMASP-1 and MASP-2

MBL-MASP Complex Formation - MBL circulates inthe bloodstream in association with MBLassociated serine proteases (MASPs), primarilyMASP-1 and MASP-2

When MBL binds to specific carbohydrate structureson the surface of pathogens, it undergoes aconformational change that allows it to associatewith MASPs, forming the MBL-MASP complex.

When MBL binds to specific carbohydrate structureson the surface of pathogens, it undergoes aconformational change that allows it to associatewith MASPs, forming the MBL-MASP complex.

When MBL binds to specific carbohydrate structureson the surface of pathogens, it undergoes aconformational change that allows it to associatewith MASPs, forming the MBL-MASP complex.

Activated MASPs- Activated MASP-2 in turns acton the complement C4, splitting into C4 and C4b

MASP-2 ; complement Cfour

Activated MASPs- Activated — in turns act on the —, splitting into C4 and C4b

Cleavage of Complement Proteins- leads to theformation of the lectin pathway C3 convertase,C4b2a.

C3 convertase,C4b2a.

Cleavage of Complement Proteins- leads to theformation of the lectin pathway —

Amplification and Effector Functions- C3convertase generated by the lectin pathwaycleaves C3 into C3a and C3b. C3b thenopsonizes pathogens, enhancesphagocytosis by immune cells, and triggers theformation of the membrane attack complex(MAC) for direct lysis of pathogens.

Amplification and Effector Functions- C3convertase generated by the lectin pathwaycleaves C3 into C3a and C3b. C3b thenopsonizes pathogens, enhancesphagocytosis by immune cells, and triggers theformation of the membrane attack complex(MAC) for direct lysis of pathogens.

Amplification and Effector Functions- C3convertase generated by the lectin pathwaycleaves C3 into C3a and C3b. C3b thenopsonizes pathogens, enhancesphagocytosis by immune cells, and triggers theformation of the membrane attack complex(MAC) for direct lysis of pathogens.

Regulation- to prevent excessive complementactivation and host tissue damage. Regulatoryproteins, such as C1 inhibitor and complementreceptor 1 (CR1), help control complementactivation and prevent complement-mediateddamage to host cells.

Regulation- to prevent excessive complementactivation and host tissue damage. Regulatoryproteins, such as C1 inhibitor and complementreceptor 1 (CR1), help control complementactivation and prevent complement-mediateddamage to host cells.

Regulation- to prevent excessive complementactivation and host tissue damage. Regulatoryproteins, such as C1 inhibitor and complementreceptor 1 (CR1), help control complementactivation and prevent complement-mediateddamage to host cells.