Intro to immunology

Question 1

Describe the replication time of bacteria compared to viruses?

Answer 1

Bacteria replicate faster than viruses

Question 2

What is the basic sequence of events that occur during a viral infection?
What type of response happens initially?

Answer 2

• inital response is the innate immune response
  -rise in type 1 interferon: interfers with replication of virus
  -peak in NK (natural killer) cells: these can recognise and lyse infected cells.
  these responses help to flatten virus replication

NEXT: adaptive response
-rise in cytotoxic t lymphocytes- recognise and lyse infected cells
-CTLs produce antibodies against the virus
This allows the complete removal of the virus

Question 3

State some differences between innate and adaptive immune responses.

Answer 3

Innate:
-from birth
-relies on pre-formed and rapidly synthesised components
-limited specificity
-involves secreting cytokines to direct cells
-limited germ line encoded receptors in each individual
Adaptive/Acquired
-acquired after exposure to the pathogen
-depends on clonal selection
-slow and SPECIFIC
-GIVES immunological memory
-antibodies produced through this only
-very large number of antigen-specific receptors in each individual that are generated during lymphocyte development by recombination of gene segments.

Question 4

what does the innate immune system allow and do?

Answer 4

• Buys time while the acquired immune system is mobilised
• evokes type 1 interferons
• activates interleukins which activate inflammatory pathways

Question 5

state some cells that are part of innate and acquired immunity

Answer 5

eosinophils, basophils, and mast cells (filled with basophil granules)

Question 6

State the two types of triggers of the innate immune response and give an example of each.

Answer 6

DAMP ( danger associated molecular patterns) – high extracellular ATP (becuase atp is a sign of danger as atp isnt useful outside cells
PAMP (pathogen associated molecular patterns) – bacterial cell wall components, dsRNA

Question 7

What does the acute phase response respond to?

Answer 7

It is an inflammatory response to tissue damage.

Question 8

What is a main clinical feature of the acute phase response and what causes it?

Answer 8

Fever – caused by Interleukin-1

Question 9

Define Actue phase protein

Answer 9

A class of plasma proteins whose plasma concentrations increase (positive acute phase proteins) or decrease (negative acute phase proteins) in repsonse to inflammation

Question 10

What are the acute phase proteins and what do they do?

Answer 10

C-reactive protein and serum amyloid protein: bind to molecules found on the cell wall of some bacteria and fungi
Mannan-binding lectin: binds to mannose sugar molecules which are not often found in mammalian cells.
once these proteins bind, phagocytes recognise these and ingest the agent.
The proteins are SOLUBLE PATTERN RECOGNITION RECEPTORS.

Question 11

What are cytokines and do they do?

Answer 11

Proteins that are solube.

• a stimulus causes a cell to produce cytokines
• cytokines diffuse, bind to specific receptors and send a signal to either upregulate or downregulate proteins.
• cytokines important in proliferation of lymphocytes

Question 12

What are the cells of the innate immune system?

Answer 12

Granular leukocytes:
Natural killer cells
-type of cytotoxic lymphocyte
-identify and kill virus: infected cell and tumour cells
Macrophages
-mononuclear phagocytes
-release cytokines as signals of danger
Granulocytes:
Basophils
-release histamines
-least abundant
-not phagocytic
Neutrophils
-polymorphonuclear neutrophils (PMN)
-nucleus is multi-lobed
-phagocytic
Eosinophils
-Bi-lobed nucleus
-important in immune response to parasites

Question 13

Draw how to nucleus looks of:

• lymphocyte
• monocyte
• eosinophil
• basophil
• neutrophil

Answer 13

Look at immunology 1 : pg 58

Question 14

What are antigens, immunogen and immunoglobins ?

Answer 14

Antigens: molecule that reacts with antibodies or T cells.
Immunogens: antigens that initate an immune response.
Immunoglobins: class of proteins

Question 15

What are the five classes of immunoglobulin and what are their distinct features?

Answer 15

G – monomer - 75% of serum Ig. It passes from mother to foetus. Involved in the secondary immune response. A – dimer – found on mucosal surfaces – has a secretory component to resist degradation by proteases found in the mucosa
M – pentamer – has 10 binding sites so is good at agglutinating pathogens. Involved in the primary immune response -10%
E – monomer – binds to basophils and mast cells and releases histamines – involved in allergic responses
D – monomer – very low serum concentration – involved in B lymphocyte signalling.

GAMED

Question 16

How do antibodies kill viruses?

Answer 16

1. Binds to virus- prevents attachment to cell
2. opsonisation- virus is coated in antibody so it can become more easily phagocytosed
3. complement-mediated lysis of membrane bound virus
4. Antibody Dependent cell mediated cytotoxicity-coating in antibody means that infected cells are more easily killed by NK cells by lysing the infected cells

Question 17

What is the difference between B cell receptors and T cell receptors?

Answer 17

B cell receptors are membrane bound form of the antibody that the B cell will secrete if activated. It can bind to intact antigens.
T cell receptors can only bind to processed antigens, which are presented on MHC molecules.
T cells: there are 2 protein chains ( alpha and beta ) which together make the TCR.

Question 18

Describe the process of clonal selection.

Answer 18

Naive lymphocytes circulate through the lymph until they meet its complementary antigen. When the lymphocyte meets its antigen it will bind and become activated and proliferate and survive. This is called clonal expansion.

Question 19

What happens to lymphocytes once they have proliferated?

How does the immune system clear pathogens?

Answer 19

Most lymphocytes die but some survive as memory cells.
Cytotoxic T lymphocytes kill infected cell.
Destroy infected cells by injecting lethal enzymes
Antibodies bind to the pathogen and direct phagocytes to come and ingest them

Question 20

What are the three main types of antigen presenting cell and what do they do?

Answer 20

Macrophages, Dendritic Cells, B cells – they pick up antigens and move to the lymph nodes (secondary lymphoid organs) where circulating T lymphocytes can meet the antigens.

Question 21

What are the primary lymphoid organs?

Answer 21

Bone marrow- B cell maturation

thymus- T cell maturation

Question 22

What are the secondary lymphoid organs?

Answer 22

Lymph nodes, Spleen, Mucosa-Associated Lymphoid Tissue (MALT)

Question 23

Where are the places lymphocytes and antigen-presenting cells recirculate through lymphatic vessels:

Answer 23

• FRom tissues
• via lymph nodes and the spleen
• INTO the blood

Question 24

how is clonal diversity generated in lymphocytes

Answer 24

B cells: immunoglobin gene segment
T cells: TCR gene segements

random genetic recombinations

Question 25

The thymus:

Answer 25

Thymus function decreases slowly from puberty, which results in a reduced production of T lymphocytes and eventual immune impairment. It is simply essential for the ‘education’ of the T lymphocytes.

Question 26

Artificially acquired passive immunity includes

Answer 26

Human intravenous immunoglobulin
Externally provided immunoglobulin is a form of passive immunity because the resident immune system is not made use of. All the other options are variations of vaccines and ALL vaccines involve the stimulation of the resident immune system to bring about an ACTIVE response.

Question 27

Clonal selection is best seen in:

Answer 27

lymphocytes

Question 28

: The spleen:

Answer 28

-contains red and white pulp
Germinal centres are sites of rapid B cell proliferation, and develop in response to antigenic stimulation. A blood-borne pathogen is likely to stimulate an immune response in the spleen, which therefore may contain germinal centres.
About other options: the spleen destroys redundant red blood cells, not white. Lymph nodes have lymphoid follicles rich in B cells, not T lymphocytes.