Kaplan Ch. 8 - The Immune System

Question 1

What is the function of the spleen as it relates to the immune system?

Answer 1

Storage of blood and activation of B cells

Question 2

Where do T cells mature?

Answer 2

The thymus

Question 3

What do T cells do?

Answer 3

They coordinate the immune system and directly kill infected cells

Question 4

What is the immune function of the lymph nodes?

Answer 4

Provide a place for immune cells to communicate and mount an attack, also a place for B cells to be activated

Question 5

What are the 2 major subdivisions of the immune system?

Answer 5

The innate immunity (non specific immune response, active all the time) and the adaptive immunity (specific immune response, developed as immune cells learn to recognize and respond to particular antigens)

Question 6

How is the adaptive immune response sub divided?

Answer 6

Humoral immunity (via B cells that produce antibodies that act in the blood)

Cell mediated immunity (via T cells that coordinate immune responses between cells)

Question 7

What are the components of the innate immune system?

Answer 7

The skin
The GI tract
The complement system
Interferons

Question 8

What is the complement system?

Answer 8

Complement system consists of proteins in the blood that at as non specific defense against bacteria, they create holes in the bacterial cell wall making them unstable

Question 9

What are interferons and what are their functions (4)

Answer 9

When a cell has been infected with a virus, they produced these proteins which:

(a) prevent viral replication and dispersion
(b) cause nearby cells to decrease production of viral and cellular proteins
(c) decrease permeability of nearby cells making it harder for them to be infected
(d) up-regulate antigen presentation on extracellular side of cell membranes

Question 10

What is a macrophage?

Answer 10

A type of agranulocyte that reside in tissues, they are derived from monocytes

Question 11

How do macrophages react when an invader enters a tissue?

Answer 11

The macrophage becomes activated and it phagocytizes the invader via endocytosis, then it digests the invader using enzymes, then it presents peptide fragments from the invader on the surface of its membrane using a protein called MHC II. MHC II binds to the pathogenic peptide and carries it to the cell surface where it can be recognized by cells of the adaptive immune system.

Macrophages also release cytokines in response to being activated, which trigger inflammation and recruit additional immune cells to respond.

Question 12

Describe the endogenous pathway for antigen presentation and the role MHC I plays in this pathway.

Answer 12

All nucleated cells display MHC I proteins. Any protein produced INSIDE THE CELL can be loaded into MHC I and presented on the surface of the cell for detection by the immune system. Thus if a cell is infected with bacteria or viral proteins these can be displayed on the outside of the cell and the immune system will recognize them as foreign and attack the cell.

Question 13

Describe the exogenous pathway for antigen presentation and the role that MHC II proteins play in this.

Answer 13

This applies to macrophages and other agranulocytes. The antigen comes from OUTSIDE the cell and is phagocytized by the cell and then the peptides are presented on the surface of the cell by MHC II.

Question 14

What are natural killer cells?

Answer 14

Certain viruses and bacteria can downregulate MHC making it harder for infection to be recognized. Natural Killer cells recognize this down regulation and induce apoptosis of the cells that are down regulating MHC. Plays a role in both immune defense and cancer defense.

Question 15

What is a neutrophil?
What is it’s target?
How can a neutrophil follow its target?

Answer 15

1) a neutrophil is a granulocyte that is in the blood, they are phagocytes
2) their targets are bacteria
3) can sense certain products given off by bacteria and follow those products via chemotaxis back to the source (the bacteria)

Question 16

What is pus?

Answer 16

Collections of dead neutrophils

Question 17

What are eosinophils?
What is their immune function?
What do they do upon activation?

Answer 17

1) granulocytes that have bright red/orange granules
2) involved in allergic reactions and invasive parasitic infections
3) they release histamine which is an inflammatory mediator. Inflammation occurs when histamine causes vasodilation, allowing other immune cells to leave the blood and enter the tissue to respond

Question 18

What are basophils?

What immune function do they serve?

Answer 18

1) granulocytes that have purple granules

2) involved in allergic reactions (similar to mast cells)

Question 19

Once an antibody binds to an antigen, what 3 outcomes are likely?

Answer 19

1) antibodies may attract other leukocytes to phagocytize those antigens
2) May cause pathogens to clump together (agglutinate) forming a large insoluble complex that is more easily phagocytized
3) May block the ability of the pathogen to invade tissues

Question 20

What process to B cells undergo to become suitable to making antibodies for pathogens?

Answer 20

B cells hypermutate their variable regions to have just the right sequence to bind to the antigen, only B cells that can bind to the antigen with high affinity will survive

Question 21

How do B cells give rise to plasma cells and memory B cells?

Answer 21

When a naive B cell binds to its antigen, it divides into a plasma cell (produce large amount of antibodies) and a memory B cell (stay in lymph nodes, await rexposure to same pathogen)

Plasma cells die eventually once immune function has been served. Memory B cells live as long as the organism does.

Question 22

What are the 2 kinds of selection that T and B cells can undergo during maturation?

Answer 22

Positive selection: cells must show that they are capable of recognizing antigens on MHC, those that cannot undergo apoptosis

Negative selection: cells must show that they do not react to host cell proteins on MHC in the absence of an infection, those that respond to strongly to self antigens on MHC undergo apoptosis (failure of negative selection to occur results in autoimmune disease)

Question 23

What are helper T cells?
What diseases affects these cells?
What antigens to helper T cells respond to?

Answer 23

1) CD4+, coordinate the immune response by secreting lymphokines that recruit other immune cells
2) HIV: helper T cells are destroyed by HIV virus, resulting in AIDS
3) MHC II antigens so mostly effective against bacterial fungal and parasitic infections

Question 24

What are cytotoxic T cells?

What antigens do these cells respond to?

Answer 24

1) CD8+ T cells, responsible for directly killing virally infected cells
2) respond to MHC I antigens

Question 25

What are suppressor T cells?

Answer 25

T cells that help tone down the immune response once an infection has been contained, also turn off or destroy self reactive lymphocytes to prevent auto immune diseases