2S [LEC]: Complement Flashcards by 3sha Ann

An integral part in mediating immune response and bridges between the innate and adaptive immunity

Complement

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Where is the C1 produced?

Intestinal epithelial cells

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Where is the factor D produced?

Adipose tissue

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Cells that produce properdin and C7

Immune cells (monocytes, macrophages, neutrophils)

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Complex series of more than 30 circulating and membrane-bound proteins

Complement

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Part of C1 that binds to the Fc fragment of the antibody

C1q

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Most abundant C protein in serum that is considered as the convergence point of all pathways and marker of inflammation

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2nd most abundant C protein in the serum

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C protein fragment that is considered a very potent opsonin

C3b

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A membrane-bound glycoprotein that binds to C3b and C4b, playing a crucial role in immune complex clearance and regulating complement activation

CR1/ CD35

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A C protein fragment that can act as a kinin activator

C2b

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C protein fragments that can act as chemotaxins

C5a, C5b, C6, C7

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C protein fragments that can act as anaphylatoxins

C3a, C4a, C5a

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Most potent C protein fragment anaphylatoxin

C5a

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C protein fragment/s that is/are responsible in the neutralization of viruses

C4b, C1

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In the alternative pathway, this C protein fragment is recognized by CR2 present in B cells to enhance its response to microbe

C3d

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C protein fragment that releases neutrophils from the bone marrow

C3c

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C protein fragment that releases hydrolytic enzymes from neutrophils

C5a

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This scientist introduced the role of complementing antibodies in destroying microorganisms

Ehrlich

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This scientist elucidated the role of C’ in the immune system

Bordet

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T/F: All the three pathways have the same components of the MAC

True

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Other than antibodies, which factors can activate the classical pathway?

CRP, Viruses, Bacteria (Mycoplasma)

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Specific part of the Fc region where the C1q binds if the antibody is an IgG

CH2

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Specific part of the Fc region where the C1q binds if the antibody is an IgM

CH3

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Parts of the C1 that act as zymogens to generate enzyme activity

C1r, C1s

Most effective IgG in activating complement

IgG3

Least effective IgG in activating complement

IgG2

First complement pathway to act

Alternative pathway

Second complement pathway to act

Lectin pathway

Last complement pathway to act

Classical pathway

The most studied complement pathway

Classical pathway

The C1q is composed of how many heads?

How many C1q heads are needed to activate the complement?

At least 2

The stalk of the C1q is made up of which structure?

Collagen

Which ion stabilizes the C1 component?

Calcium

T/F: C2a is the lighter fragment than C2b, and will then be distributed throughout the body for biological functions

False (C2b is lighter than C2a, C2a will bind to C3b to produce C5 convertase)

In the classical pathway, what are the components of the C3 convertase?

C4b2a

In the classical pathway, this cleaves the C3

C3 convertase/ C4b2a

In the classical pathway, what are the components of the C5 convertase?

C4b2a3b

Which component of the C5 convertase will bind to C5, permitting the cleavage into C5a and C5b

C3b

What are the components of the membrane attack complex (MAC)?

C5b6789

This complement pathway can also act as an "amplification loop"

Alternative pathway

Other than IgM and IgG, which antibody can also activate the alternative pathway?

IgA

The alternative pathway was first described by ___

Pillemer

The stabilizing component of the alternative pathway

Properdin

In the alternative pathway, what are the components of C3 convertase?

C3bBb

In the alternative pathway, what are the components of C5 convertase?

C3bBb3b

The pathway that serves as a defense mechanism during infancy

Lectin pathway

A protein that binds to carbohydrate

Lectin

What produces mannose-binding lectin?

Liver in acute-phase inflammatory reactions

Identify the regulator of the complement system: Binds C1r2s2, causing dissociation from C1q

C1 inhibitor

Identify the regulator of the complement system: Blocks the association of C4b and C2a

C4b-binding protein (C4bBP) Complement receptor type I Membrane cofactor protein (MCP)

Inhibitor-bound C4b is cleaved by ___

Factor I

Identify the regulator of the complement system: In alternative pathway, these will prevent the binding of C3b and factor B

CR1 Membrane cofactor protein (MCP) Factor H

Inhibitor-bound C3b is cleaved by ___

Factor I

Identify the regulator of the complement system: Inactivates C3b and C4b, thereby regulating C3 convertase

Factor I

Identify the regulator of the complement system: Regulates alternative pathway by targeting C3b

Factor H

Identify the regulator of the complement system: Prevents bystander lysis

Decay accelerating factor/ DAF (CD55)

Identify the regulator of the complement system: Prevents the insertion of C5b67 MAC component into the membrane

S protein

Identify the regulator of the complement system: Binds C5b678, preventing assembly of poly-C9 and blocking formation of MAC

Homologous restriction factor (HRF) Membrane inhibitor of reactive lysis (MIRL)

Identify the regulator of the complement system: Dissociates C1r and C1s from C1q

C1 inhibitor

Identify the regulator of the complement system: Cleaves C3b and C4b

Factor I

Identify the regulator of the complement system: Cofactor with I to inactivate C3b; prevents binding of B to C3b

Factor H

Identify the regulator of the complement system: Acts as a cofactor with I to inactivate C4b

C4-binding protein

Identify the regulator of the complement system: Prevents attachment of the C5b67 complex to cell membranes

S protein/ Vitronectin

Identify the complement receptor on cell membranes: Cofactor of factor I; mediates transport of immune complexes

CR1 (CD35)

Identify the complement receptor on cell membranes: B-cell co-receptor for antigen with CD19

CR2 (CD21)

Identify the complement receptor on cell membranes: Adhesion and increased activity of phagocytic cells

CR3 (CD11b/ CD18) CR4 (CD11c/ CD18)

Identify the complement receptor on cell membranes: Important receptor of the Epstein-Barr virus

CR2 (CD21)

Identify the regulator of the complement system: Dissociates C2b or Bb from binding sites, thus preventing formation of C3 convertase

DAF (CD55)

Identify the regulator of the complement system: Prevents insertion of C9 into cell membrane

MIRL (CD59)

Identify the regulator of the complement system: Cofactor for Factor I cleavage of C3b and C4b

MCP (CD46)

Identify the C protein associated with the condition: Lupus-like syndrome

C1r, C4 deficiency

Identify the C protein associated with the condition: Sex-linked agammaglobulinemia, severe combined immunodeficiency

C1q deficiency

Identify the C protein associated with the condition: Most serious, severe recurrent infections

C3 deficiency

Identify the C protein associated with the condition: Neisseria infections

C5-C8, MBL, Properdin deficiency

Identify the C protein associated with the condition: Paroxysmal nocturnal hemoglobinuria (PNH)

DAF, MIRL deficiency

Identify the C protein associated with the condition: Recurrent pyogenic infections

Factor H, Factor I deficiency

Identify the C protein associated with the condition: Pneumococcal diseases

MASP-2 deficiency

C protein deficiency that has no known disease association

C9 deficiency

Identify the C protein associated with the condition: Leiner's disease Gr (-) skin and bowel infection

C5 dysfunction

Identify the C protein associated with the condition: Erythroderma dysquamativum

C5 dysfunction

Identify the C protein associated with the condition: Reynaud's phenomenon

C7 deficiency

Identify the C protein associated with the condition: Scleroderma like syndrome

C7 deficiency

Identify the C protein associated with the condition: Hereditary angioedema

C1INH deficiency

Identify the C protein associated with the condition: Pyogenic infections

Factor D deficiency

Immunologic assay used for C1 inhibitor

ELISA

Most common assay for classical pathway that is crude screening test, measuring the amount of serum required to lyse 50% of standardized concentration of sensitized RBCs

Hemolytic titration (CH50) assay

Similar to CH50 but magnesium chloride and ethylene glycol tetracetic acid are added

AH50

In AH50, which component is removed to measure alternative pathway?

Calcium (since it stabilizes the C1 in classical pathway)