Adaptive Immunology - Dr. Hudig

Question 1

Name 4 pathogens that the immune system deals with and state whether it is intracellular or extracellular.

Answer 1

1. Bacteria - can be extracellular or intracellular.
2. Yeast and fungi - extracellular.
3. Viruses - intracellular.
4. Parasites - can be intracellular or extracellular.

Question 2

Give several examples of intracellular bacteria.

Answer 2

M. tuberculae, listeria, salmonella and shigella.

Question 3

What is CD4?

Answer 3

A protein found on the surface of T helper cells.

Question 4

What is CD8?

Answer 4

A protein found on the surface of CD8 cytotoxic T cells.

Question 5

Give examples of some parasites.

Answer 5

Plasmodium falciparum, Ascaris, Giardia.

Question 6

What 2 cell types control viruses -in the innate system and the adaptive immune system.

Answer 6

In innate immune responses, NK cells will target viruses and in the adaptive immune response, CD8 cytotoxic T cells target viruses.

Question 7

Describe the adaptive immune system.

Answer 7

The adaptive immune system is an inducible system that utilizes T and B lymphocytes to target pathogens. It is specific, each T and B cell has receptors that are different and that are specific to an antigen. These receptors are not directly genome encoded. The response takes at least 5+ days to develop, eliminates infections faster than innate immunity and lasts the lifetime of the immune person because it generates antigen -specific memory.

Question 8

Where are T lymphocytes made?

Answer 8

T -cells are formed in the bone marrow and travel to the thymus to differentiate and mature. They are the effectors of cell-mediated immunity.

Question 9

Where are B lymphocytes made?

Answer 9

B-cells are formed and mature in the bone marrow. They secrete antibody proteins after encounter with their cognate antigens. They are are effectors of humoral immunity.

Question 10

What are antigens?

Answer 10

Foreign or non-self structures recognized by T cells, B cells and antibodies.

Question 11

What are epitopes?

Answer 11

The structures within antigens that bind to B and T cell receptors for antigens.

Question 12

What do T cells most always recognize?

Answer 12

Foreign peptides that are displayed in MHC molecules. CD4 T helper cells recognize antigen in MHCII molecules. CD8 cytotoxic T cells recognize antigen in MHCI molecules.

Question 13

What do B cells recognize?

Answer 13

B-cells recognize antigen from any foreign substance that it has a specific receptor for.

Question 14

What do antibodies recognize?

Answer 14

Antigens can be proteins, carbohydrates and lipids.

Question 15

What is an MHC?

Answer 15

MHC is major histocompatibility complex - it is a receptor on all cells of the body except for RBC’s - specifically the MHCI receptor.

Question 16

Where are MHCII molecules located?

Answer 16

These receptors can be conditionally expressed on many cells but is principally found on antigen presenting cells such as macrophages, dendritic cells and B cells.

Question 17

Where are MHCI molecules located?

Answer 17

On the surface of all nucleated cells of the body except for RBC’s.

Question 18

How do T cells recognize antigen?

Answer 18

An APC or other cell displays a foreign peptide in an MHC molecule on its surface. A T-cell has a T-cell receptor that is specific for that antigen and it recognizes the peptide-MHC combination.

Question 19

What is dual recognition?

Answer 19

It refers to T cells. T cell receptors for antigen must have the specificity to recognize both the foreign peptide and the MHC molecule.

Question 20

Describe T cell receptors for antigen.

Answer 20

TCR’s are heterodimers that are made from 2 chains. 95% of the time these are an alpha and beta chain and 5% of the time these are a gamma and a delta chain.

Question 21

What are CD proteins?

Answer 21

CD or cluster of differentiation proteins are located on T cells and they bind to MHC molecules. CD4 is on the surface of T-helper cells and it acts as a co-receptor for TCR and binds to MHCII molecules. CD8 is on the surface of cytotoxic T cells and it acts as a co-receptor for TCR and binds to MHCI molecules. CD3 is on the surface of all T cells and acts as a signal molecule.

Question 22

Can T cells recognize free or soluble peptides?

Answer 22

No, the peptide must be displayed in an MHC molecule.

Question 23

How do T cell response start?

Answer 23

T helper cells with a cognate receptor interact with an antigen presenting cell with an antigen in MHC protein. The antigen specific T cell will divide forming clones. The clones have more functions than the original T cell that responded. The clones secrete cytokines - specifically IL-2.

Question 24

What does the cytokine IL-2 do?

Answer 24

IL-2 causes prolifération of activated T-cells, is a growth factor for B cells and can activate NK cells and macrophages.

Question 25

How long does it take for T cells to divide?

Answer 25

6 hours.

Question 26

Are T helper cells required for adaptive immune responses?

Answer 26

yes

Question 27

Describe an immunoglobulin monomer (Ig).

Answer 27

They are composed of two light chains and two heavy chains held together by disulfide bonds. Within one Ig the light chains are identical to eachother and so are the heavy chains. There are constant regions and variable regions. The constant regions determine the isotype and the variable regions are the antigen binding regions. The chains form a Y shape, the top is where antigen binds and the bottom is where the antibody binds to other molecules and they are held together by a hinge region which gives flexibility.

Question 28

Do both chains of the Ig make up the variable or antigen binding region?

Answer 28

yes

Question 29

Do B cells make antibodies of different specificity?

Answer 29

No, once an antibody becomes a plasma cell it produces antibodies of only one specificity.

Question 30

Which Ig chain determines the isotope or class of the Ig?

Answer 30

The heavy chain.

Question 31

What is Fab and Fc?

Answer 31

Antibodies can be cleaved by proteases and when they are they break up into typical fragments. Two Fab fragments that can bind antigen and one Fc fragment that binds to other molecules and effector cells. The functional difference between isotope classes lies within the Fc fragment.

Question 32

describe the different types of regions on antigens that antibodies recognize.

Answer 32

1. conformational determinant (binding region of antigen) - only binds to antibody when protein is folded because it is determined by conformation.
2. linear determinant - determinant is linear not conformational. Some antibodies can only recognize in denatured protein and some antibodies can recognize in both native and denatured protein - depends on the antigen and antibody.
3. neoantigenic determinant - determinant is revealed by processing (proteolysis) of antigen. Neoantigens may promote autoimmunity if self proteins are cleaved.

Question 33

Do specific immune responses take time?

Answer 33

Yes, because the specific B and T cells must both proliferate before becoming effector cells. T cells help B cells and kill microbes and B cells make antibodies.

Question 34

How long do memory lymphocytes last?

Answer 34

The lifetime of the person.