Immunity- part 3 ! ( 3 LOD)

Question 1

Characteristics of the 3rd LOD

Answer 1

> Specificity: the ability to recognise and respond to particular antigens
Memory: The immune system remembers the original exposure to a pathogen and therefore produces a larger and more rapid response to the second exposure of the same pathogen
Reaction Time: The reaction time at the first exposure is slow but faster at subsequent exposures

Question 2

Components of 3 LOD

Answer 2

> Antibodies, Antigen-presenting phagocytes, B and T lymphocytes, complement proteins and cytokines

Question 3

Types of B cells

Answer 3

> Plasma B cells: Produce and secrete antibodies
Memory B cells: Produce immunological memory

Question 4

What are constant and variable regions?

Answer 4

Constant Region: that does not vary between antibodies of the same class
Variable Region: that differs between antibodies

Question 5

Function of antbodies

Answer 5

> Directly identify and bind to extracellular foreign antigens, by EITHER neutralising or tagging them for destruction

Question 6

Neutralisation of pathogens and toxins

Answer 6

Pathogens: Antibodies to the surfaces antigens on pathogens and form a coating that neutralises pathogens by blocking their receptors so that the pathogens cannot attach to healthy body cells and infect them

Toxins: Antibodies bind to bacterial/animal toxins and venoms. The antibodies neutralise the harmful effects of the toxin/venom

Question 7

Opsonisation

Answer 7

> Antibodies bind to surface antigens on the pathogen to form antigen-antibody complexes and tag the pathogen for destruction. Activating phagocytes and complement proteins, leading to the destruction of the pathogen

Question 8

Agglutination ( clumping )

Answer 8

Antibodies bind to the surface antigens on pathogens to form antigen-antibody complexes which causes various pathogens to clump together and be more visible to the immune system

Question 9

Precipitation ( solidify)

Answer 9

> Antibodies bind to soluble antigens, making them insoluble causing them to precipitate out of the solution, creating a solid that is much more visible to the immune system ( cross linking between antigens and antibodies )

Question 10

Inflammation

Answer 10

> Antibodies can trigger the release of histamine causing inflammation, also activate a complement cascade

Question 11

First exposure process to antigen

Answer 11

> A new antigen gains entry to the body reaches the lymph nodes via APC. Naive B cells do not recognise it. BUT Antigen comes across a B cell that does recognise it and bind to it
(CLONAL SELECTION)
Helper T cells that have also bound to the antigen release cytokines to activate the correct B cells
Helper T cells and the binding of the antigen to its selected B cells activates the B cell to differentiate and proliferate ( divide ) in to plasma B and memory B cells. (CLONAL EXPANSION)
Most of these cells differentiate into short lived plasma cells that secret soluble antibodies against the specific antigen
Memory B cells remain in the lymphoid tissue for after the infection has resolved. They initiate immune responses more rapidly and strongly upon re-exposure to the same antigen, producing large amount of the specific antibody

Question 12

Classes of Antibodies

Answer 12

Antibodies are also known as Immunoglobulins (Ig)
> IgM: First to be secreted in an infection, causing agglutination of cells containing antigens
> IgG: Activate complement proteins in blood and neutralise toxins directly
> IgA: Neutralise pathogens in respiratory, digestive and reproductive systems
> IgE: Initiate inflammation after a pathogenic infection, causes allergic reactions to non-pathogenic agents

Question 13

Main functions of Lymphatic System

Answer 13

> Is a transport network and monitors the body for signs infection
Production and maturation of immune cells/ lymphocytes ( T and B cells )
Removes of excess fluids from body tissues and absorbs transports fats and fatty acids
Allows APC
Drains fluid and proteins back into the cardiovascular system
Lymph nodes are sections which are filled with leukocytes and detect/destroy pathogens
Transport lymphocytes and APCs to the lymph nodes, stimulating the adaptive immune response

Question 14

What is the lymph

Answer 14

> Lymph is the fluid in the lymphatic system that gets squeezed out of blood vessels
Interstial fluid surrounding the tissues gets filtered through the tiny holes between the capillaries into the lymphatic system
Lymph can only move one direction due to the presence of valves in lymphatic vessels

Question 15

Primary lymphoid organs?

Answer 15

> Where mature lymphocytes (B & T cells) develop from precursor cells
Bone Marrow: Where B cells mature
Thymus: Where T cells mature after being released from bone marrow

Question 16

Self tolerance?

Answer 16

Where tolerance of lymphocytes develops and any B and T cells that target self-cells are eliminated

Question 17

Lymph nodes?

Answer 17

> Located in the armpits, groin, neck and abdomen
Lymph nodes are main sites of the adaptive immune response
Location for antigen recognition where APC display their antigens to their specific T and B lymphocytes -> Leading to expansion of appropriate lymphocytes involved in adaptive immunity

Question 18

Cellular Immunity?

Answer 18

> Eliminates infected cells with T cell activity ( cytotoxic T cells )
Targets self-cells that have been infected/ cancerous/intracellular pathogen ( T cell receptors bind to intracellular pathogens
T cells cannot detect free antigens (extracellular pathogens)

Question 19

Different types of T Cells

Answer 19

> Cytotoxic T cells: Directly killing ( lysis + apoptosis)
Helper T Cells: Communication via cytokines (soluble protein)
Memory T cells: Maintain memory for the future
Suppressor T cells: Avoids over reactions

Question 20

Vaccines

Answer 20

-> Vaccinations involved the use of a vaccine to induct artificial active immunity
-> Vaccines need to be highly specific to the pathogen to initiate an adaptive immune response resulting in immunological memory

Question 21

Types of Vaccines

Answer 21

-> Live attenuated
-> Inactivated
-> Subunit

Question 22

Live Attenuated Vaccines

Answer 22

-> Contains weakened form of pathogen which is still able to reproduce but does no cause disease symptoms
-> Safe for people with a healthy immune system, however can cause disease in those with weakened immune systems
-> A single dose can initiate a strong adaptive immune response
-> Results in immunological memory (long term immunity)

Question 23

Inactivated Vaccines

Answer 23

-> Contains killed version of the pathogen. Viruses are not living, so they are referred to as inactivated
-> Disease causing agent is unable to replicate

Question 24

Advantages and Disadvantages of Inactivated Vaccines

Answer 24

ADs- Results in production of many different antibodies, as they contain many different antigens. Safe for use in people with weakened immune systems

DISs- Stimulate a weaker immune response so require a booster to maintain long term immunity

Question 25

Subunit Vaccines

Answer 25

-> Contain specific pieces of the pathogen selected for their ability to induce adaptive immune response. Those that contain multiple antigens induce broader immunity, because they will induce the production of antibodies directed against multiple antigens.

Question 26

Advantages and Disadvantages of Subunit Vaccines

Answer 26

ADs- Safe for use in people with weakened immune systems. Easier to store than live attenuated vaccines

DISs- Stimulate a weaker immune response so require a booster to maintain long term

Question 27

Immune Response to Vaccines ( Action of Vaccines)

Answer 27

1. Primary Exposure to vaccine
2. The vaccine is administered, and the immune system recognises the pathogen as having non-self antigens.
3. Memory Cell Formation
4. This stimulates a humoral response, even though they don’t show symptoms, resulting in the formation of memory B cells.
5. Secondary exposure to ‘real’ pathogen.
6. A second exposure to the same non-self antigen occurs, resulting in a faster and greater number of antibodies production
7. This neutralises the pathogen before it causes disease and results in the formation of more memory B cells.

Question 28

What is the Antigenic Drift

Answer 28

-> Occurs when small changes (mutations) in the genes of viruses leads to changes in the surface proteins of the virus. Changes accumulate over time. Which results in viruses that are closely related to one another, meaning they also have similar antigenic properties.
-> Means that antibodies created by the immune system against one virus will likely recognise and respond to similar flu viruses

Question 29

What is the Antigenic Shift

Answer 29

-> Is an abrupt, major change in a virus. Results in a new surface proteins. leads to a new virus strain ( subtype). Antigenic shift can happen if a virus from an animal population gains the ability to infect humans which means that surface proteins are different enough that most people do not have immunity to the new virus

Question 30

Herd Immunity

Answer 30

-> Essential for the protection of those who cannot be vaccinated or who have suppressed immune systems.
-> If there is widespread immunity in a population, then there is very little chance that an infected person will encounter someone who is not immune, and so the pathogen has very little opportunity to invade a new host, and the disease is not able to spread.