8.3 HY The adaptive immune system

Question 1

What are the two divisions of the adaptive immune system?

Answer 1

1. Humoral Immunity
2. Cell-mediated (cytotoxic immunity)

Question 2

What are the main cells of the adaptive immune system? (x2)

Answer 2

B-cells- mature in bone marrow and spleen
T-cells- mature in spleen

Both created in the bone marrow.

Question 3

What do B- cells do?

Answer 3

They are stimulated by antigens and divide and produce antibodies that neutralize invaders or tag them for killing.

Question 4

What do T-cells do?

Answer 4

a killer T-cell destroys and infected cell in which it detects the presence of antigens. other T-Cells- such as helper and regulatory types, coordinate the immune response.

Question 5

What happens when an antibody that is free flowing binds to an antigen.

Answer 5

1. May attract other leukocytes to phagocytize those antigens immediately (opsonization).
2. Antibodies may cause pathogens to clump together or agglutinate, forming a large insoluble complex that can be phagocytized.
3. Can block the ability of the pathogen to invade tissue, essentially neutralizing it.

Question 6

What happens when an antigen comes into contact with an antibody that is attached to a b-cell?

Answer 6

It causes activation of that cell, resulting in its proliferation and formation of plasma and memory cells.

Question 7

What happens when an antigen comes into contact with an antibody that is attached to a mast cell?

Answer 7

it causes degranulation, releasing histamine and causing and inflammatory allergic reaction.

Question 8

What is hypermutation and clonal selection?

Answer 8

When b-cells make antibodies, it is complex.
Only the b-cells that it goes many renditions to make the excact, right antibody that will attach to the antigen, called hypermutation.

The ones that don’t or aren’t quite right or are not too specific are destroyed, called clonal selection.

Question 9

what are naive b-cells?

Answer 9

They are B cells who have not yet been exposed to the antigen to make antibodies. They are laying in wait in the lymph nodes.

Question 10

In what type of cells can B-Cells be categorized? (x2)

Answer 10

1. Plasma cells- produce a large amount of antibodies. Die off after awhile
2. Memory B-Cells- stay in the lymph nodes and wait for the next exposure. May live the lifetime of the organism. (made with vaccines)

Question 11

What is the difference between the primary response and the secondary response?

Answer 11

Primary response: Initial activation of the b-cells to produce plasma cells and memory b-cells
Secondary response: this is what happens after the second exposure to an antigen, a long time later. The memory cells remember the antigen and rapidly proliferate, causing more plasma cells to be produced.

Question 12

What is positive and negative selection in regards to T-cells?

Answer 12

Positive selection- refers to allowing only the maturation of cells that can respond to the presentation of antigen on the MHC (cells that cannot respond to MHC undergo apoptosis because they will not be able to respond in the periphery).

Negative selection- causing apoptosis in cells that are self-reactive.

T-cells can undergo clonal selection as well. Only those with the highest affinity for a given antigen proliferate.

Question 13

What is thymosin?

Answer 13

It is a peptide hormone secreted by thymic cells that help to facilitate the maturation of t-cells.

Question 14

What does CD mean in immunology?

Answer 14

CD means cluster of differentiation, and includes cell-surface markers that can be detected by the lab technique called flow cytometry; these markers give an indication of the types o leukocytes under investigation, how many are present, and their state of maturity.

Question 15

What are the three major types of T-cells? (x3)

Answer 15

Helper T-Cells- called CD4 T-cells, coordinate the immune response by secreting chemicals known as lymphokines which can recruit other immune cells and increase their activity. They respond to antigens presented on MCH=II molecules, therefore most effective against bacterial, fungal, and parasitic infections.

Suppressor T- CellsExpress CD4, but also Foxp3. This helps to tone down the immune response once infection has been adequately contained. They turn off self-reactive lymphocytes to prevent autoimmune disease, called self-tolerance

Killer (Cytotoxic) T-Cells- also called CD 8 t-cells- are capable of directly killing virally infected cells by injecting toxic chemicals that promote apoptosis into the infected cell. They respond to MHC-I molecules, and therefore are most effective against viruses.

Question 16

What do Helper T-Cells do?

Answer 16

helper t-cells- called CD4 T-cells, coordinate the immune response by secreting chemicals known as lymphokines which can recruit other immune cells and increase their activity. They respond to antigens presented on MCH=II molecules,

Therefore they are most effective against bacterial, fungal, and parasitic infections.

Mnemonic: CD x MHC= 8

Question 17

What do cytotoxic/killer cells do?

Answer 17

killer (cytotoxic) t-cells- also called CD8 t-cells- are capable of directly killing virally infected cells by injecting toxic chemicals that promote apoptosis into the infected cell.

They respond to MHC-I molecules, and therefore are most effective against viruses.

Mnemonic: CD x MHC= 8

Question 18

What do suppressor or regulatory T-cells do?

Answer 18

Express CD4, but also Foxp3.

Foxp3 helps to tone down the immune response once infection has been adequately contained.

They also turn off self-reactive lymphocytes to prevent autoimmune disease, called self-tolerance

Question 19

What do memory T-cells do?

Answer 19

They are similar to memory B-cells, and they lay in wait until exposure to the same antigen. When activated, they carry out a more robust immune response

Question 20

What are the five types of infections that can occur?

Answer 20

Virus, bacteria, fungi, parasite (protozoa, worms, insects)
Prions (no immune defense)

Question 21

Walk me through what happens if a bacteria infects someone…

Answer 21

1. Macrophages and other antigen presenting cells engulf the bacteria and release inflammatory mediators.
2. Cells present the pathogen on their surface with MHC-II
3. Cytokines attract inflammatory cells, including neutrophils and macrophages.
4. Mast cells are activated by the inflammation and degranulate, resulting in histamine release and increasing the leakiness of the capillaries, augmenting the effectiveness of the immune system.
5. The dendritic cell leaves the affected tissue and travels to the nearest lymph node, where it presents the antigen to B-cells.
6. B cells produce the correct antibody proliferate through clonal selection to create plasma cells and memory cells.
7. Antibodies travel through the bloodstream to the affected tissue, where they tag the bacteria for destruction.

At the same time:.
1. Dendritic cells are also presenting the antigen to T-cells, activating a T-cell response. In particular, CD-4.
2. Specific T cells release interferon gamma, which activates macrophages and increases their ability to kill bacteria.

After the pathogen has been eliminated, plasma cells die, memory B and T cells remain, allowing for a faster immune response at a later time.

Question 22

What happens in a viral infection, walk me through what happens?

Answer 22

1. After the viral infection, cell will begin to produce interferons, which reduce the permeability of nearby cells, and decreasing the ability of the virus to infect these cells. It reduces the rate of transcription and translation in these cells (decreasing the ability of cell to multiple), and causes systemic systems (malaise, muscle aching, fever, and so on).
2. Infected cells present intracellular proteins on their surface with MHC-I, which will include some viral proteins.
3. CD8+T cells will recognize the MHC-I and antigen complex as foreign and will inject toxins into the cell to promote apoptosis, preventing the spread to nearby cells.
   3.2 If the cell downregulates MHC-I molecules, NK cells will recognize the absence of MHC-I and will accordingly cause apoptosis.
4. One the pathogen has been cleared, memory t-cells will be generated that allow for a much faster response to upon a second exposure.

Question 23

What are self-antigens?

Answer 23

They are the proteins and carbohydrates present on the surface of every cell of the body. They signal that the cell is not foreign and should not be attacked.

Autoimmunity occurs when this difference is not recognize and the body attacks itself.

The body tries to prevent autoimmune reactions in the T-cell and B-cell maturation processes, through negative selection.

Question 24

What are hypersensitivity reactions?

Answer 24

They occur when the body thinks that an antigen is deadly but it really is not.

Question 25

What is the difference between active and passive immunity?

Answer 25

Active: the immune system is stimulated to produce antibodies against a specific pathogen.

Passive: Transfer of antibodies to an individual. This may occur through giving Ig, or through the transfer from the mother to the fetus.