Complement

Introduction

• The complement system is one of the major effector mechanisms of

humoral immunity

• Is an important effector mechanism of innate immunity.

• Jules Bordet 1919

• The complement system consists of serum and cell surface proteins

• Activation of complement involves the sequential proteolysis

• zymogens

Complement nomenclature

•C3

C3a

ConvertaseC3b

The classical pathway of complement activation

C1q molecule

The classical pathway of

complement activation

The classical pathway

of complem

ent activatio

n

The alternative pathway

Tickover

The alternative

pathway

• The alternative-

pathway C3 and C5

convertases are both

stabilized by

properdin (factor P)

Lectin Pathway

Lectin Pathway of

Complement

Activation

Ficolin

MAC formation

MAC formation

late steps of complement activation and formation of the MAC

Regulator of complement activation

Regulator of complement activation

Inhibition of the formation of C3 convertases

Factor I-mediated cleavage of C3b

Regulator of complement activation

Regulation of formation of the MAC

The Roles

The Good

Functions of complement

Receptors for Fragments of C3

Inflammatory effects of complement

The bad

C3 deficiency

•Sever recurrent infection with encapsulated bacteria

•Begain shortly after birth

MAC (C5-C9) deficiency

•Susceptible to N. meningitidis infection

Complement deficiency

The ugly

C1q, C2 and C4 deficiency

•Associated with the development of SLE.

C1INH Deficiency

PNH

Deficiency in

DAF or CD 59

fetal loss in antiphospholipid syndrome.

Examples of pathological conditions involving the complement system.

Clinical effects of complement deficiency

The End