Immunity

Question 1

What is the lymphatic system?

Answer 1

network of vessels
which reach almost all
tissues

Question 2

What are the roles of the lymphatic system?

Answer 2

1) fluid recovery
2) immunity
3) lipid recovery

Question 3

What is fluid recovery?

Answer 3

recovers fluid not picked up by cappilaries

Question 4

What is immunity?

Answer 4

forgein materials and cells picked up in fluid

Question 5

What is lipid recovery?

Answer 5

in small intestine

Question 6

What are the components of the lymphatic system?

Answer 6

1) lymph
2) lymphatic vessels
3) lymphatic cells
4) lymphatic tissues
5) lymphatic organs

Question 7

What is lymph?

Answer 7

recovered fluid

Question 8

What are lymphatic vessels?

Answer 8

transport lymph (leaky capillaries

Question 9

What are lymphatic cells?

Answer 9

T and B lymphocytes
NK cells
macrophages

Question 10

What are lymphatic tissues?

Answer 10

aggregates of lymphocytes and macrophages (eg in mucosa)

Question 11

What are lymphatic organs?

Answer 11

where lymphatic cells are connected and enclosed in connective tissue (eg red bone marrow)

Question 12

What are the three lines of defences?

Answer 12

1) physical barriers
2) macrophages, natural killer cells, inflammation (non specific, innate immunity)
2) acquired immunity mediated by lymphocytes

Question 13

What is an example of a physical barrier?

Answer 13

skin

Question 14

What are examples of chemical barriers?

Answer 14

acidic pH of sweat and sebaceous secretions

fatty acids and hydrolytic enzymes

Question 15

Why are mucous membranes considered barriers of defence?

Answer 15

mucus traps inhaled particles (dust)
watery saline layer allows cilia to push mucus to pharynx
particles do not enter cells

Question 16

In what way is the body considered a hostile environment and can therefore be seen as a defence?

Answer 16

enzymes in saliva
acidic pH in stomach
proteolytic enzymes in bile and small intestine

Question 17

What chemical defences are there in the body?

Answer 17

soluble factors found in blood serum include:

1) interferons (anti-viral protection)
2) complement protins (lead to pathogen destruction)

Question 18

What are the two types of immunity?

Answer 18

1) innate immunity (first line of defence)
-rapid, non-specific, present from birth
2) acquired immunity
= recognition of ‘non self’ antigens
- mediated by B cells (antibodies) and T cells

Question 19

What is innate immunity?

Answer 19

antigen non-specific
rapid (minutes to hours)
no memory

Question 20

What does innate immunity consist of/involve?

Answer 20

includes physical and chemical barriers (skin)
phagocytes and natural killer cells
soluble mediators (eg complement)
pattern recognition molecules

Question 21

What is adaptive immunity?

Answer 21

antigen specific
slow (days)
memory

Question 22

What does adaptive immunity consist of/involve?

Answer 22

lymphocytes
antigen recognition molecules (B and T cell receptors)
secreted molecules (eg antibody)

Question 23

What is the role of natural killer cells?

Answer 23

1) NK cells release perforins which polymerise and form a hole in the enemy cell membrane
2) granzymes from NK cell enter perforin hole and degrade enemy cell enzymes
3) enemy cell dies by apoptosis
4) macrophage engulfs and digests dying cell

Question 24

What is phagocytosis?

Answer 24

1) Macrophage
recognises a
pathogen.
2) Macrophage engulfs
the pathogen and
forms a phagosome.
3) Lysosome fuses with
phagosome.
4) Pathogen
enzymatically
digested.

Question 25

What is acquired immune response?

Answer 25

specific response to antigens capable of immunological memory can be cell mediated or antibody mediated recognises antigens which are non-self

Question 26

What is an antigen?

Answer 26

molecule capable of inducing an immune response in the host organism

Question 27

What are antigen presenting cells?

Answer 27

a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells.

Question 28

How do antigens and antigen presenting cells interact?

Answer 28

• Antigen presenting cells “sample” contents of the cell and present on the outside. • Antigens are small fragments of peptide which bind to the MHC II. • The MHC II with antigen is then moved to the surface of the antigen presenting cell. • When a corresponding T cell binds to the antigen it becomes activated.

Question 29

What is the overall process of immune response?

Answer 29

1) microbes enter through break in the skin and are phagocytosed by dendritic cells 2) activated dendritic cell carries microbial peptides to local lymph node 2) activated dendritic cell activated specific T cells to respond to microbial peptides bound to MHC proteins on dendritic cell surface 3) activated cells migrate to site of infection via the blood

Question 30

What are the different types of T cell?

Answer 30

1) naïve T cells 2) effector T cells 3) Memory T cells

Question 31

What are naïve T cells?

Answer 31

initially bind to antigen

Question 32

What are effector T cells?

Answer 32

usually short lived 1) Cytotoxic T cells: which can kill infected cells 2) Helper T cells: secrete cytokines to recruit more cells and to co-ordinate the attack

Question 33

What are memory T cells?

Answer 33

remain to enable a fast response for subsequent infections by the same antigen T cells proliferate and undergo mitosis in response to activation. All daughter cells have T cell receptors specific to the original antigen. These T cells remain as Memory T cells. If you are infected with the same antigen again, memory cells allow a faster and more effective response.

Question 34

What are T helper cells?

Answer 34

stimulate response by T and B cells

Question 35

What is the difference between T and B cells?

Answer 35

T cells 1) bind to antigens on antigen presenting cells 2) release cytokines to recruit/activate cells tp destroy pathogen 2) antigens bind to MHC of host cells B cells 1) bind to antigens directly on pathogens or on APCs 2) produces antibodies 3) cannot respond to intracellular pathogens

Question 36

What is the process of humoral immunity?

Answer 36

1) antigen recognition: 2) antigen presentation: 3) clonal selection: 4) differentiation: 4) attack:

Question 37

What happens during antigen recognition of humoral immunity?

Answer 37

immunosuppresent B cells exposed to antigen. Antigen binds only to B cells which complementary receptors

Question 38

What happens during antigen presentation of humoral immunity ?

Answer 38

B cell internalises antigen and displays processes eptitope. Helper T cells binds to B cell and secretes interleukin.

Question 39

What happens during clonal selection of humoral immunity?

Answer 39

interleukin stimulated B cell to divide repeatedly and form a clone

Question 40

What happens during differentiation of humoral immunity?

Answer 40

some cells of the clone become memory B cells most differentiate into plasma cells

Question 41

What happens during attack of humoral immunity?

Answer 41

plasma cells synthesise and secrete antibodies. Antibody employs various means to render antigen harmless

Question 42

How do antibodies render antigens harmless?

Answer 42

1) covering pathogenic sites (neutralisation) 2) binding them together to form complexes which are harmless and can be removed or destroyed (agglutination) 3) activate a pathway of events (complement pathway) which leads to cell lysis and clearance by other cells