Complement

Question 1

What is complement?

Answer 1

a complex set of distinct serum proteins (more than 30) that interact in a very specific way to mediate and enhance host defense reactions

Question 2

Where are most complement proteins synthesized?

Answer 2

liver

Question 3

Where is C1 mainly produced?

Answer 3

intestinal epithelial cells

Question 4

Where is factor D made?

Answer 4

adipose tissue

Question 5

How many complement component participate in the classical pathway?

Answer 5

9

Question 6

What two immunoglobulin classes are capable of activating complement?

Answer 6

IgG and IgM

Question 7

How many immunoglobulin Fc fragments are needed for complement activation?

Answer 7

2 IgG fragments or 1 IgM fragment

Question 8

What is the end result of the complement cascade (in conjunction with the antigen-antibody reaction)?

Answer 8

irreversible cell damage and lysis

Question 9

How can serum complement be inactivated?

Answer 9

heating to 56*C or by allowing the serum to age

Question 10

Why would complement need to be inactivated for certain serology testing?

Answer 10

can cause false + by lysing cells and/or utilizing their antigen in the procedure

Question 11

What is anaphylatoxin?

Answer 11

mediator of inflammation that initiates the release of histamine from mast cells and increases vascular permeability, which allows the flow of serum antibody and complement to the affected area; result of the reaction of C3 and C5

Question 12

What role does calcium play in complement activity?

Answer 12

required to hold together the C1 complex of C1qrs

Question 13

What is magnesium’s role in complement activity?

Answer 13

required for C2 to become involved in the complement cascade

Question 14

What is the order of complement components in the classical pathway?

Answer 14

C1, C4, C2, C3, C5, C6, C7, C8, C9

Question 15

Which complement component is the most abundant?

Answer 15

C3

Question 16

Which component is cytolytic?

Answer 16

C8

Question 17

What does the presence of C9 do?

Answer 17

accelerates cell lysis

Question 18

What is the alternate pathway for complement?

Answer 18

bypass mechanism that does not require interaction between C1, C4, and C2; natural mechanism for defense against microbial invasion (can be activated by exposure, before antibody is available)

Question 19

What was the alternate pathway originally called, and why?

Answer 19

properdin pathway; was thought that properdin initiated it

Question 20

What are the activators of the alternate pathway?

Answer 20

Gram-positive and -negative bacteria; fungi and yeast; certain viruses; certain parasites; and some tumor cells

Question 21

How many plasma proteins comprise the alternate pathway?

Answer 21

6

Question 22

Which plasma proteins participate in the alternate pathway that are not seen in the classical pathway?

Answer 22

factor B, factor D, properdin, factor I, and factor H

Question 23

What specifically do factor I and factor H do in the alternate pathway?

Answer 23

prevent the process from proceeding uncontrolled

Question 24

What is the third pathway of complement activation called?

Answer 24

lectin pathway

Question 25

Does the lectin pathway require antibody?

Answer 25

no

Question 26

What is the major constituent in the lectin pathway, and how does it work?

Answer 26

mannose- (or manner-) binding lectin (MBL); adheres to mannose, which is found mainly in the cells walls or outer coating of bacteria, viruses, yeast, and protozoa

Question 27

Is MBL normally present in the serum?

Answer 27

yes, but it also increases during an initial inflammatory response

Question 28

Can complement lyse bacteria?

Answer 28

yes, a few species (primarily Gram-negative)

Question 29

What effect does complement have on opsonization?

Answer 29

cells with C3b on their surface tend to be more readily phagocytized; these cells tend to aggregate together which serves to promote the process