The immune system

Question 1

what are the two forms of the immune system?

Answer 1

innate defence system

adaptive defence system

Question 2

what is immunology?

Answer 2

the body’s ability to defend itself against pathogens, that is anything that can produce disease

Question 3

pathogens may be…?

Answer 3

bacterial infection
viral infection
fungal infection
toxin

Question 4

what is innate immunity?

Answer 4

Non specific
1st line of defence: physical and chemical barriers
2nd line of defence: internal defences
Targets all pathogens

Question 5

what is adaptive immunity?

Answer 5

Acquired immunity
The body’s ability to recognise specific foreign substances – antigens
Antigens are substances capable of triggering an immune response through the production of antibodies to destroy the pathogens.
This system builds immunological memory

Question 6

what is Leukopoiesis?

Answer 6

The production of white blood cells to leukocytes

Leukocytes are formed from stem cells in the red bone marrow along with red blood cells (haemopoieses)

Question 7

what is the lymphatic system?

Answer 7

carries excess interstitial fluid from tissues back to cardiovascular circulation and provides locations for immune cells to monitor the body

Question 8

how does the lymphatic system work?

Answer 8

porous lymphatic vessels take in fluids from extracellular space and carry them through lymph nodes, where immune cells scan the fluids for foreign particles

Question 9

why is the lymphatic system needed?

Answer 9

fluid must be returned to circulation via lymphatics to maintain cardiovascular function, and lymph nodes are necessary to monitor the body for infection

Question 10

name 3 granular cells?

Answer 10

mast cells- Produce histamine
Involved in allergies
basophils
Eosinophils- produce enzymes to break down the histamine and reduce inflammation

Question 11

what are neutrophils?

Answer 11

Migrate to the site of inflammation
Secrete cytokines – which alerts other cells within the immune system
Squeeze into the tissue: diapedesis 
Ingest pathogen 
Die forming pus
largest proportion of blood leukocytes

Question 12

what are macrophages?

Answer 12

These are the largest phagocytes
Two types:
FREE macrophages: circulate in the blood and lymph systems
FIXED macrophages attached to fibres in specific organs.
Cytoplasmic extensions pulls in pathogen and digests it
Can ingest multiple times

Question 13

what are monocytes?

Answer 13

Phagocytes
Develop in bone marrow  
Migrate to the area of inflammation
Arrive after neutrophils 
Differentiate into:
Macrophages
Dendritic cells

Question 14

what are dendritic cells?

Answer 14

Antigen presenting cells which allows other cells of the immune system to recognise the antigen
Travel to the lymph nodes and present to T-cells

Question 15

name the three lymphocytes?

Answer 15

B Cells
T Cells
Natural killer cells

Question 16

explain B- lymphocyte cells ?

Answer 16

Develop immuno-competence in red bone marrow
*Ability to differentiate pathogens from normal cells

Every B -cell has its own antibodies
Travels in blood and lymph
Meet the antigen it has antibodies for binds to it

Clones itself to produce:
Effector cells which produce antibodies to bind to the antigen
Memory cell: secondary immune response

Question 17

explain T- lymphocyte cells?

Answer 17

Develop in red bone marrow, mature in the thymus.
Acquire antigen specific receptors and differentiate into
HELPER T –CELLS (CD4 cells): produce cytokines which activate B cells, T cells and macrophages
CYTOTOXIC T-CELLS (CD8 cells): destroy foreign cells or body cells with foreign agents. Includes tumour cells and transplant cells.

MEMORY CELLS: versions of helper and cytotoxic T cells which remain in the body and can proliferate if the same antigen invades the body

Question 18

explain natural killer cells?

Answer 18

Lymphocytes found in blood and lymph
Part of the 2nd line of defence along with phagocytes
All cells have a major histocompatibility complex (MHC1s) protein on the surface membrane. NK cells detect cell where MHC1s are abnormal or reduced.
NK cells bind to the diseased cell and release perforin and granzymes which trigger apoptosis (programmed cell death)

Question 19

what is the 1st line of innate immunity defence?

Answer 19

physical barrier created by surface membrane=
Skin
Mucous linings (acidic – inhibits bacterial growth)
Mucus traps foreign particles
chemical barriers=
Lysosomes in lacrimal eye fluid
Hydrochloric acid in stomach
Antimicrobial proteins (defensins) eg Genito-urinary tract
Sweat: high salt concentration

Question 20

what are the 2nd line of defence internal innate

defences ?

Answer 20

phagocytes
natural killer cells
inflammation
fever

Question 21

explain the process of inflammation?

Answer 21

Triggered by MAST cells in connective tissue, release histamine.

Excess fluid from swelling is absorbed by the lymphatic system and cleaned before being reabsorbed into the blood stream.

Leaky capillaries make it easier for phagocytes and lymphocytes flowing in the blood stream.

Question 22

explain the process of phagocytosis?

Answer 22

phagocytes engulf pathogen, vesicle merges with lysosome which contains acid, lysosome digest pathogen, exocytosis, antigen presentation

Question 23

explain process of fever?

Answer 23

Macrophages can release pyrogen chemicals
Target hypothalamus
Raise temperature
Increases metabolism
Causes the Liver/ Spleen to retain iron and zinc – limit bacterial growth

Question 24

name the two adaptive immunity responses?

Answer 24

humoral responses

cellular defences

Question 25

explain the humoral response?

Answer 25

Antigen binds to surface receptor on B-cell
B-Cell produces clone cells
effector cells (plasma cells) which produce high levels of free floating antibodies
memory cells
Antibodies mark antigens with a sticky surface for destruction by phagocytes: Opsonisation
Block the binding sites on viruses so they cant bind to tissues: Neutralisation
Can bind to multiple antigens at the same time: Agglutination
Release chemicals to signal phagocytes and lymphocytes

Question 26

how is passive immunity acquired?

Answer 26

Babies acquire immunity from 
Maternal from womb
Ready made placenta/ breast milk
Can’t produce effector cells or memory cells
Won’t remember antigen

OR plasm cells from antibodies from a donor

Question 27

explain cell mediated immunity response?

Answer 27

Antigen presenting cells: APC
Macrophages
Dendritic cell
B- Cell
Helper T cells only bind to one specific combination of MHC II
Effector T cells proliferate
Memory T cells: keep a record for future immunity
Cytotoxic T cells: become fully activated releases perforin and granzymes, triggering apoptosis