Complement 3 Flashcards

1
Q

Which component of C3b binds to the surface of the microbe?

A

The thioester domain

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2
Q

Why does factor H not bind to microbial cells?

A

It has an affinity for sialic acid residues and glycosaminoglycans which are present on host cells but not microbial cells

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3
Q

Which domains of factor H bind to complement?

A

1,2,3,4

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4
Q

Which domains of factor H bind to surfaces?

A

19,20

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5
Q

What kind of binding does factor H do on nonself surfaces?

A

Weak binding

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6
Q

What kind of binding does factor H do on self surfaces?

A

Strong

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7
Q

What does weak binding lead to?

A

complement activation

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8
Q

What does strong binding lead to?

A

Complement -ve regulation

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9
Q

How can pathogens evade complement?

A

They have produced proteins that stabilise factor H, so the C3 is degreade on their surface

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10
Q

What is on the surface of smallpox that mimics the function of factor H?

A

SPICE

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11
Q

Role of C4 binding protein (C4BP)?

A

Inhibit C3 convertase

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12
Q

Additional roles of complement?

A

phagocytosis and clearance

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13
Q

What can the complement receptor on phagocytes bind to?

A

Antigens/microbes that have been opsonised by C3b

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14
Q

What happens once the complement receptor on a phagocyte has bound to an antigen/microbe?

A

The antigen/microbe can be taken up

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15
Q

How does HIV enter macrophages?

A

Complement activation and deposition of C3b on the surface of the virus

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16
Q

How is complement involved in clearance?

A

Cells that carry complement receptors can take up large immune complexes

17
Q

What happens if there is a build up of immune complexes in the kidneys?

A

Kidney necrosis

18
Q

Which cells are important in clearing immune complexes bc they have complement receptor 1 on their surface?

19
Q

Where are complement receptors found?

A

Erythrocytes, leukocytes, B and T cells, follicular dendritic cells, neutrophils and macrophages

20
Q

Which cells is complement receptor 1 linked to?

A

Erythrocytes, leukocytes

21
Q

Which cells is complement receptor 2 linked to?

A

B cells, T cells, follicular dendritic cells

22
Q

Which cells is complement receptors 3 and 4 linked to?

A

Macrophages, neutrophils

23
Q

Which complement receptor is widely expressed in cells?

A

C3a receptor

24
Q

Where are C5a receptors found?

A

Lymphoid cells

25
Q

Most common complement deficiency?

26
Q

What are many complement deficiencies linked to?

A

Meningococcal infections