Immunology Overview

Question 1

What is the basic structure of an antibody?

Answer 1

Two heavy chains and two light chains, held together by disulfide bonds. Antibody divided into constant (Fc) region (heavy chain only) and antigen binding (Fab) region (heavy + light chains)

Question 2

What are the three main types of T cells?

Answer 2

Cytotoxic T cells, helper T cells and regulatory T cells

Question 3

Which T cell can destroy virus-infected cells?

Answer 3

Cytotoxic T cells

Question 4

Which MHC class of molecules are found on the surface of most cells in the body?

Answer 4

MHC Class I

Question 5

Which MHC class of molecules is expressed exclusively on antigen presenting cells?

Answer 5

MHC Class II

Question 6

What type of antibodies can bind virus outside of the cell and keep the virus from entering the cell or reproducing once it has entered?

Answer 6

Neutralizing antibodies

Question 7

In the alternative pathway, once C3b is stabilized by reacting with a molecule on the cell surface of the bacteria, which complement molecule binds next? What happens next?

Answer 7

Protein B binds to C3b, then complement protein D comes along and clips off part of B to yield C3bBb

Question 8

Why is C3bBb called a convertase?

Answer 8

When attached to the surface of bacteria, C3bBb acts like a “chain saw” that can cut other C3 proteins and convert them to C3b.

Question 9

Which complement protein is cleaved when C3bBb is combined with C3b in the alternative pathway?

Answer 9

C5

Question 10

Which complement proteins form the membrane attack complex? Which create the “stalk” and which create the “channel”?

Answer 10

C5, C6, C7, C8, C9

C5b, C6, C7, and C8 create stalk. C9 creates the channel.

Question 11

What 3 defense mechanisms do mammals have that keep the alternative complement pathway in check?

Answer 11

1. C3b can be clipped to an inactive form by proteins in the blood, which is accelerated by MCP enzyme on the surface of host cells.
2. Decay accelerating factor (DAF) - protein on host cells that accelarates destruction of convertase, C3bBb by other blood proteins
3. Cd59 (protectin) - cell surface protein that prevents incorporation of C9 molecules into nascent MACs

Question 12

Complement works quickly/slowly

Answer 12

Quickly

Question 13

What is the central player in the lectin activation pathway?

Answer 13

Mannose-binding lectin (MBL)

Question 14

How dose mannose-binding lectin activate the complement system?

Answer 14

MBL binds to MASP. When MBL binds to lectin on microorganisms, MASP acts as a covertase to clip C3 complement to make C3b, which binds to surface of microorgansism. This causes complement activation.

Question 15

What is iC3b?

What can and can’t iC3b do?

Answer 15

Smaller fragment of C3b that has been clipped, inactivated, and no longer able to form MACs.

Can still opsonize microorganism to promote binding of phagocytes for phagocytosis of organisms.

Question 16

What is the fuction of C3a and C5a?

Answer 16

Chemoattractants for macrophages. Can alo contribute to anaphylactic shock (referred to as anaphylatoxins).

Question 17

Resting macrophages present many/few MCH II molecules on their surface.

Answer 17

Few. They don’t need to do much antigen presentation in a resting state.

Question 18

What three states can a tissue macrophage be in?

Answer 18

Resting, primed and hyperactivated.