IMMUNOSERO Lecture: Lesson 5 - Complement System (part 1 and 2)

Sheep anti serum

What antiserum did Bordet added that contained antibodies specific to V. cholerae which caused lysis?

Pillemer

discovered an antibody-independent pathway which they termed as 'Classical Pathway

Activation

refers to the conversion of several latent proteins (zymogens) to an enzymatic form.

56°C, 30 min

The temperature range that inactivates the complement

true

T/F:

Activation of complement involves the sequential proteolysis of proteins to generate enzymes with proteolytic activity

a. Lysis of cells, bacteria, and viruses

b. Opsonization

c. Binding to specific complement receptors on cells of the immune system, triggering specific cell functions, inflammation, and secretion of immunoregulatory molecules

d. Immune clearance - removal of antigens, antigen-antibody complexes, and materials produced after an immune response

e. Anaphylactic activity - side effect of activation of complement system

Enumerate the how highly is the cascade regulated

regulatory proteins

Complement activation is inhibited by?

Soluble proteins

found in serum, freely floating as zymogens; responsible for lysis of microbial cells; serum complement proteins

Cell-bound proteins

found in plasma, attached to the surface of normal cells; control or inhibit activity of zymogens to prevent lysis of own cells by the complement system. Complement system is able to recognize own cells due to the proteins attached and foregoes destroying them.

hepatocytes

what cell produces the vast majority of complement components?

C1q

what is produced in the intestinal epithelial cells?

Adipocytes

where does factor D produced

Properdin and C7

these are produced in monocytes and macrophages

Monocytes, macrophages, cells of the synovial tissues, and astrocytes

What cells have the ability to synthesize all components of the classical and alternative pathways

Classical pathway

Alternative pathway

Mannose-Binding Lectin (MBL) pathway

enumerate the Three major complement activation pathways are present in human serum

9 proteins

how many proteins are there in the Classical pathway?

C1 C4 C2 C3 C5 C6 C7 C8 C9

state the order of sequence of activation

Order of Discovery

what order does these set of numbers imply?

C1 C2 C3 C4 C5 C6 C7 C8 C9

inactive protein

zymogen is synonymous with?

C6-C9

what complements that do not undergo proteolytic cleavage. They participate in the cascade as is

iC4b

What is the inactive form of C4b

Greek lowercase letters (α, β, γ)

Polypeptide chains of a native complement protein are designated by?

small letter "a"

When zymogens are cleaved , How do we identify the smaller fragment?

C4b

C4 is cleaved and produces C4a and C4b. Which is the larger fragment?

C4b.

Which fragment participates in the complement activation?

C3a and C3b.

C3 undergoes proteolysis. What are the fragments produced?

The larger fragment

Which participates in the reaction?

C3a

when C3 undergoes proteolysis, what is The byproduct?

more than 30

How many proteins make up the pathway?

soluble

What is the characteirstic of the zymogen complement subset is considered?

Classical pathway

this complement activation begins with the Ag-Ab complex

Alternative pathway

a complement activation that is initiated by cell-surface constituents that are foreign to the host; Ab-independent

Lectin pathway

a complement activation that is also Ab-independent.

activated by binding MBL to mannose resideues on glycoproteins or carbohydrates on the surface if microorganisms

C1

What is the recognition unit of the complement system?

Calcium

in the recognition unit, what is needed to stabilized : C1q, C1r, and C1s

False

As long as magnesium is present in serum, C1r and C1s remain associated with C1q

"Staple" configuration

What do you call when a pentameric IgM is bound to an Ag?

Planar configuration

If it's a ciculatin g IgM, what does it signify?

IgA, IgE, and IgD

immunoglobulins that CANNOT activate the classical pathway

T

C1r and C1s has catalytic and interaction domains which induces mechanical stress when C1q binds to the surface.

first amplification process

C4 is the first activation unit or also called as?

smaller fragment (e.g. C4a, C2b)

upon activating a proteolytic zymogen, what is bounded to a to receptor present on mast cells and basophils which induces degranulation and release of inflammatory mediators including HISTAMINE.

C4b2a

C3 convertase is expressed also as?

C3 convertase

What is the enzyme involve in cleavage of C3 and C5?

Truelala

T/F:

C1 complex does not cleave just one C4 and one C2 molecules instead it proteolytically cleaves hundreds of molecules

C3

what proteolytic enzyme denotes the thrid activation unit / central molecule of complement activation? Furthermore it is also the major amplification process

C5 convertase

this enzyme is produced by the bond of C3b and C3 convertase. What is the enzyme?

C4b2a3b

other term of C5 convertase

False ; C5, C5b

T/F:

The cleaving of C4 with deposition of C4b at another site on the cell membrane constitutes the beginning of the membrane attack complex (MAC)

Mini miss na kitaAAA huhu

Hello! madlang pipol! Mabuhay!

C5-C9

Enumerate the proteolytic enzyme responsible for the membrane attack complex

C5b678

This MAC enzyme induces lysis of some cell because it forms trimeric protein which inserts to the lipid bilayer

false ; Gram neg organisms

T/F:

Gram-positive organisms are susceptible to destruction by MAC. This is because it does not have a lipid bilayer making it susceptible

Alternative pathway

This kind of pathway uses nos C1, C4 or C2 because it uses four serum proteins: C3, Factor B, Factor D, Properdin. What is this pathway?

true

T/F:

Alternative pathway is antibody-independent

e IgG, IgA, and IgE to activate your alternative pathway: it has to be in complexes

If the alternative pathway is antibody independent, why are there immunoglobulins in its initiators?

Fungal cell walls

Yeasts

Dextran

give 3 examples of binding sites for C3bBb (C3 convertase)

Factor D

A serine protease with a MW of 24,000

Its only substrate is bound factor B

Magnesium ion

when factor D is bound to factor B, what ion is present for it to become activated and cleaves factor B into 2 protein fragments

false; Factor D

T/F:

Factor B has the lowest plasma concentration of all the complement proteins (2 μg/ml)

properdin

It functions only a stabilizing complement protein. does not play a role in the activation; it does not initiate it.

true

T/F:

C3, without any antigen-antibody immune complex formation, is hydrolyzed by water once there is an antigenic substance exposure

sialic acid

What acid hinders the C3 to destroy our own host cells?

C3bBb

What is the other term of C3 convertase in the alternative pathway?

C3bBbP (stabilized C3 convertase)

When properdin binds with C3bBb, the enzyme stabilizes. what is produced?

C3bBbP3b

Sometimes, C3b molecule that was cleaved by your stabilized C3 convertase may bind to the stabilized C3 convertase instead of the surface molecule, forming another molecule called?

C5 convertase

C3bBbP3b is also called as your?

Lectin Pathway

This pathway is also called as the MBL pathway / Mannose-binding Lectin Pathway

Lectin

a complement proteins that bind to a carbohydrate

Mannose

a carbohydrate at the surface of microorganisms

False; Antibody-independent

T/F:

Lectin Pathway is an antibody-dependent pathway

MBL (MANNOSE-BINDING LECTIN)

an acute phase protein which binds to mannose residues on glycoproteins or carbohydrates on the surface of microorganisms. These are also structurally similar with C1q

MBL-MASP-1/2 complex

WHat protease mimics the activity of C1r and C1s, causing cleavage and activation of C4 and C2, producing C4b, C2a, and then C4b2a?

cell-bound complement proteins

What are the system regulators that control the activation of the complements?

True

T/F:

Majority of the system regulators are aimed at halting accumulation of C3b because C3b is the largest and most abundant complement protein

C1 inhibitor or C1INH glycoprotein

REGULATION OF COMPLEMENT:

Its main role is to inactivate C1 by binding to the active sites of C1r and C1s. Clr and Cls become instantly and irreversibly dissociated from C1q. Clq remains bound to antibody, but all enzymatic activity ceases.

C4b-binding protein (C4BP)

abundant in the plasma. In adition that, Inhibits further formation of C3 convertase in the classical and lectin pathway because it is capable of combining with either fluid-phase or bound C4b

Complement receptor type 1 (CR1)

known as CD35

Membrane cofactor protein (MCP)

known as CD46

most efficient cofactor for factor I-mediated cleavage of C3b

Decay accelerating factor (DAF)

CD55

capable of dissociating both classical and alternative pathway C3 convertases

Factor H

principal soluble regulator of the alternative pathway

acts by binding to C3b, thus preventing the binding of factor B

acts as a cofactor that allows factor I to break down C3b

S protein

Also known as vitronectin

protein interacts with MAC, the C5b67 complex as it forms in the fluid phase and prevents it from binding to cell membranes

Membrane Inhibitor of Reactive Lysis (MIRL)

a CD59 which Block formation of the membrane attack complex. MOreover, its Main function is to bind to C8 and prevent insertion of C9 into host cell membranes

Homologous Restriction Factor (HRF)

Prevent formation of the MAC on the surface of autologous (normal) cell

true

T/F:

Complement proteins also serve as a means of linking innate and natural immunity. They act as opsonins to facilitate destruction by phagocytic cells, and they play a major role in uptake and presentation of antigens so a specific immune response can occur.

Anaphylatoxin

Small peptide that causes increased vascular permeability, contraction of smooth muscle, and release of histamine from basophils and mast cells

C3a, C4a, and C5a

example of anaphylatoxin

Chemotaxin

drives the Cell to the source of antigen concentratio

Opsonization

acilitates phagocytosis and clearance of foreign substances, and it is one of the key functions of the complement system

Complement testing

used to assess complement deficiencies in proteins of the classical and alternative pathways

CH50

What measure overall C' activity of classical pathway

AH50

measure overall C' activity of alternative pathway

CH50

HEMOLYTIC

ASSAY

uses Sheep RBC (SRBC). Sheep RBC are incubated with Anti-Sheep RBC (anti-SRBC) IgG antibodies to form EA complexes (antigen-antibody immune complexes)

AH50 ASSAY

uses rabbit erythrocytes.

Rabbit erythrocytes are incubated with serum of patient (in absence of Ab)

determine if which complement pathway is deficient

what do we determine in conducting the Measurement of Overall Complement Activity?

determine which of those proteins under that pathway is deficient (particular component that is deficient is identified)

What do we expect in measuring the Measurement of Complement Components

RADIAL IMMUNODIFFUSION (RID) & NEPHELOMETRY

2 tests performed in the Measurement of Complement Components

NEPHELOMETRY

Technique in which light scatter, occurring as a result of contact with a non-soluble particle, is measured

alternative pathway

acts as a natural means of defense against infection; it is triggered not by antigen- antibody combination but by the presence of microorganisms. T

lectin pathway

involves nonspecific recognition of microorganisms by means of sugars such as mannose that are common constituents of microbial cell walls but that are distinct from those found on human cell surfaces