Introduction

Question 1

What is an immune system

Answer 1

A system of biological structures and processes that functions to kill pathogens and tumors

Question 2

Know the self vs non self concept

Answer 2

Everything that is non self doesn’t mean it should be destroyed. A good example of this is bacteria in the GI tract

Question 3

Why do we study immune system

Answer 3

Because it has pathology associated with it

Question 4

Innate vs Adaptive

Answer 4

Question 5

Describe the innate immune response

Answer 5

1. It has pre existing structures like skin, mucosa, pH in stomach and proteases in saliva
2. Response typically occurs at the site of infection

Question 6

What are the 3 mechanisms of innate immune response

Answer 6

Three major mechanisms:

• Phagocytosis: neutrophls, macrophages, dendritic cells
• Target cell lysis: neutrophils, macrophages, NK cells
• Inflamamtion: cytokines and chemokines

Question 7

How does immune system identifies self and non self

Answer 7

The immune system cells have PRMs (Pattern Recognition Molecules) on them that are used to idetnify patterns. Specificly they idenitfy PAMPs (Pathogens Associated Molecular Patterns).

PRMS are basically receptors.

Question 8

How are phagocytes involved in pattern recognition

Answer 8

They phagocytose the foregin pathogen and present the antigen to other immune system cells as a danger signal to warn other white blood cells

Question 9

How does the innate immune system and the adaptive immune system tranfer information about disease and pathogens

Answer 9

Mainly the dendritic cells phagocytose the pathogens and they transport it to the lymph nodes where they present the PAMPs via the MHC II. Lymphocytes in the lymph nodes are then activated

Question 10

Where is the innate and adaptive immune system activated

Answer 10

Innate is activated at the site of infection whereas the adaptive is activated at the lymph nodes and the spleen

Question 11

Describe the B cell (4) and T cell (2) receptors

Answer 11

B cell receptors are:

• Glycoprotein complexes
• Consist of variable and constant region
• Can be either solouble (Ab) or membrane bound (B cell receptor)

For TCRs

• Multiprotein complexes
• Also consist of variable and constant region

Question 12

What does the antibodies and T cells bind to

Answer 12

Antibodies can bind to pretty much anything whereas T cells only bind to peptides

Question 13

What are the 5 properties of adaptive immunity

Answer 13

1. Specificity - recognizes one pathogen at a time
2. Specialization - response to each pathogen is optimized
3. Memory - reponse is quick and more vigorous to recurrent infections
4. Nonreactivity to self antigens - prevents autoimmunity
5. Cloncal expansion - large number of effector cells are made in response to a pathogen

Question 14

Clonal Selection Theory

Answer 14

1. All antigens on a B cell or a T cell are identical, so a given B cell or T cell can only recognize 1 antigen
2. To be immune to a large number of antigens, we need many many different lymphocytes
3. The concequence for the above 2 points is that relatively few lymphocytes recognize a given antigen

In the picture, the brown cell becomes the dominant lymphocytes in that person’s body

Question 15

Explain the concept of immunologic memory

Answer 15

1. Specific to the antigen that the body was first exposed to
2. The body becomes more sensitive to the antigen
3. Secondary immune response is more robust and quick
4. Memory cells are long lived since they differentiate from naive cells

Question 16

Define Naive, Effector and Memory cells.

What are their respective life spans

Answer 16

Naive Cells: Mature lymphocytes that have not been activated yet, they have not encountered an antigen in their lives, lifespan = months

Effector Cells: Differentiated lymphocytes that are either helpter T cells, cytotoxic T cells, plasma cells that are actively involved in fighting off the pathogen. Lifespan = days

Memory cells: Differentiated lymphocytes, typically long lived, that can bceome effector cells upon reencounter with the antigen, lifespan = years.

Question 17

What are the phases of adaptive immunity

Answer 17

There are 5 phases:

1. Antigen recognition or antigen presentation: Naive T cell identify the pathogena and naive B cells identify the antigen presented by the APCs
2. Lymphocytes activation: this involved clonal expansion and differentiation
3. Antigen elimination: this involved humoral immunity and cell mediated immunity which results in elimination of the pathogen
4. Contraction phase: active T cells and B cells undergo apoptosis
5. Memory: Only memory B cells and T cells remain in the body from the encounter

Question 18

What is a cytokine and a chemokine

Answer 18

Low molecular weight, solouble proteins that trigger activation, proliferation or cell death.

A chemokine is a low molecular weight protein that tells the cell that they need to go somewhere

Question 19

How do cytokines act

Answer 19

Question 20

What are the types of lymphoid organs

Answer 20

There are 2 types, primary and secondary, which can also be categorized as central and peripheral

1. Primary: These are the organs of myelogenesis and lymphogenesis. These consist of bone marrow and thymus
2. Secondary: There are the sites where immune cells are concentrated to optimize immune response. These are spleen, lymph nodes, tonsil, peyer’s patch.

Question 21

What is the interplay between innate immune response and adaptive immune response

Answer 21

Innate immune response identifies the antigen and tries to contain it. At the same time it talks to the cells in the lymphoid tissue to trigger a highly specific adaptive immune response against the antigen. Once the adaptive immune response is developed it contains the antigen and then it relies on the innate immune response to finish off the pathogen. See the attached slide