introduction to immune responses

Question 1

What is the immune response?

Answer 1

comprises an interacting network of cells and molecules responsible for mounting an immune response when appropriate

Question 2

What is the function of the immune response? (3)

Answer 2

protect the body against invasion by microorganisms
stopping tumour formation
fight against infection

Question 3

Physical barriers to infection

4 groups

Answer 3

Skin 
Mucosal surfaces 		mucus
						cilia
						secretions
Commensal organisms - competition
Acid – kills infectious agents

Question 4

Skin

what does it do?
how do organisms overcome it?

Answer 4

Skin provides a protective cover
Organisms can overcome this barrier
Cuts or damaged skin 
Insect bites
Animal bites

Question 5

mucus lining
where?
what do they do?

Answer 5

There are areas of the body that are not covered by skin

Mucus traps organisms

Question 6

Can you name infectious agents that infect the genital tract?

what is always present in gental tract? how does this help?
what are consequence if antibitoics remove this?

Answer 6

Commensal organisms present in the genital tract

There is always a competition

Example; if you are treated with antibiotics that result in removing the bacteria that are normally resident in the genital tract, what are the consequences?
Less competition more likely to get infection – thrush – candida

Question 7

Innate immune system: Effector cells

7 cells

Answer 7

Phagocytes: neutrophils, macrophages, dendritic cells
mast cells, eosinophils, basophils
natural killer (NK) cells

Question 8

Phagocytes - function?

origin?

Answer 8

identify, ingest, destroy pathogens

origin: generated in bone marrow

Question 9

Phagocytes: Macrophages

what do they start off as?

how do phagocyte kill organism?

Answer 9

Macrophages
They start as monocytes then they are activated in the tissue and become macrophages.

Microbe must attach to phagocyte
Ingestion initiated
Organism enters the phagocyte in a vacuole
Destroyed within this vacuole

Question 10

Some phagocytes become Dendritic cells

where do they enter?
what do they do?

Answer 10

They enter skin, mucosa, tissues
capture microbes
phagocytosis
eliminate the microbe

Question 11

Phagocytic cells -what else do they do?

Answer 11

Eliminating the microbe is not the only task. They present these as antigens to T cells

Question 12

Do phagocytes work alone?

Answer 12

Phagocytes don’t work alone
They need help in attaching to and destroying organisms – mainly bacteria.
Complement helps.

Question 13

What are complements?

what 3 roles do they have?

Answer 13

Complement are a group of proteins
Task number one is to help attachment of micro-organisms and phagocytes
They also act as an enzyme cascade system.
Enhance phagocytic function

Question 14

Phagocytes
We know they Kill and They can also clear dead cells
But do they have any other roles? (2)

Answer 14

Produce substances that attract other cells to the site– chemotactic substances
Increasing vascular permeability – allow immune cells to get in.

Question 15

Innate immunity - not just Phagocytes. What other responses? (3)

Answer 15

Acute Phase Proteins
C Reactive Protein (CRP)
inflammation

Question 16

Inflammation – Why? (2)

Answer 16

Attract cells to the site.

Help killing and clearance of organisms

Question 17

Interferon - what make them? function?

Answer 17

Many immune cells make interferons

Task – to interfere with viruses infecting other cells.

Question 18

Natural killer cells

innate system - jobe?

Answer 18

Surveillance role

Any cell that has changed is a target for killing

Question 19

Summary – innate immunity

barriers to infection?
important cells?

Answer 19

Barriers to infection
Mucus
Saliva
Acid of stomach
Tears
Sweat
Cilia
Cough
Organisms that compete
Flushing action of urine

Phagocytes
Complement
C-reactive protein
Other inflammatory response cytokines
Interferons
Natural killer cells
Important points – low specificity and no memory

Question 20

Adaptive Immune System
difference?
tow key cells?

Answer 20

B lymphocytes
T lymphocytes
Adaptive immune system - high specificity

Question 21

PRIMARY LYMPHOID ORGANS (2)

Answer 21

Bone marrow

Thymus

Question 22

Secondary Lymphoid organs (4)

Answer 22

Blood
Spleen
Lymph
Lymph nodes

Question 23

Lymphocyte development from primary to secondary organ - what is special about the cells?

Answer 23

Production of >108 different cells, each with different specificity
to
1 cell = 1 specificity

Question 24

Lymphocytes and antigens

what is special about the cell?
how do B-lymphocytes recognise anitgens?
how do T-lymphocytes recognise antigens?

Answer 24

Each cell has (slightly) different cell-surface receptor for antigen, and hence binds to different antigen

B-lymphocytes recognise antigen through immunoglobulin receptors on their surface

T-lymphocytes recognise antigen through T-cell receptors

Question 25

Lymphocyte response to antigen

survival for non-dividing cells?
what do they lymphocytes do in the mean time?
what happens if they bind to an antigen?

Answer 25

> 10^8 lymphocytes = >10^8 different specificities in your body

the non-dividing cells – live for years

patrolling – waiting to meet the one (few) antigens their receptors bind to

when (if) their receptors bind to an antigen, they proliferate

Question 26

What do B lymphocytes do?

what do they make?
two example?

how do we make correct anitbodies?

Answer 26

B cells make antibodies
Immunoglobulins

Two examples are;
IgM – made first
IgG – made later

We have many B cells
Each with own receptor
Selection of specific B cell
Proliferation of clone
Make correct antibodies

Question 27

How do antibodies work?

2 ways they work?
example of how these two ways work?

Answer 27

Neutralisation
Example – coat virus with antibody – stop it entering cells

Opsonization
Coat micro-organism with antibody
Phagocytic cells have receptors for antibody
Phagocytes can now attach to the bacterium
Engulf
Kill
This is team work!

Question 28

Memory of immune cells

first time vs second time?

Answer 28

First time we see an infectious agent we take time to respond.
Second time we meet the same agent – very quick response
We remember the enemy!
This is why we call it adaptive immunity

Question 29

How do T cells work?

what do thye do? how?

Answer 29

Helper T cells – very helpful
help B cells make antibody
How?
When activated they release chemicals known as cytokines
Cytokines are the helpful chemicals that encourage B cells to work

Question 30

Problem T cells face

what can’t they see? how does the body overcome this?

Answer 30

T helper cells can not see the virus on their own.
They need help to see antigens
Help provided by phagocytic cells
They phagocytose the infectious agent, destroy the virus or bacterium
But they carry the antigens and present these to T helper cells.
Team work!

Question 31

T cytotoxic cells
They cannot see viruses or bacteria on their own either!
So how do they kill?

use the example of cell infected by virus to explain
significance of MHC

Answer 31

Cell infected e.g. virus
Virus wants to replicate
Virus proteins made inside cell
Cell cannot hide infection
Virus proteins appear on cell surface – attached to a cell protein called major histocompatibility antigen MHC
T cytotoxic cells can see MHC and virus protein together
Killing begins