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Immunology > Adaptive Immune System > Flashcards

Adaptive Immune System Flashcards

1
Q

What is the adaptive immune system

A

Specific to pathogen
- Ab receptor combines with a specific antigen
Delayed if new pathogen
Immunological memory
Antibody (humeral) mediated - B lymphocyte
Cell mediated
- T lymphocyte CD4 + CD8

Lymphocytes circulate in blood looking for pathogen that matches their TCR or Ab which is BCR

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2
Q

Where do T cells mature

A

Thymus

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3
Q

Where do B cells mature

A

Bone marrow + LN

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4
Q

What happens to T cell in thymus

A

Develop CD markers and TCR
CD4 = T helper
CD8 = cytotoxic
NK cells

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5
Q

What happens to B cells as they mature

A

Become either
Plasma cell and produce Ab - which is a BCR
Memory B cell

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6
Q

What happens when B and T cells are matured

A

Migrate to secondary lymphoid organs where they encounter antigen and become activated

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7
Q

What does CD4 TCR recognise

A

MHC II

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8
Q

What does CD8 TCR recognise

A

MHC I

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9
Q

What does MHC II present / react too

A

Extracellular pathogens

MO / dendritic cells endocytose and present MHC II to CD4 to initiate immune response (activates CD4)

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10
Q

What does MHC I present / react

A

On all nucleated cells + platelet

Present intracellular pathogens e.g. virus / cancer

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11
Q

What is central tolerance

A 
Inactivation of cells that are bad 
Occurs in thymus and bone marrow
If self reacting BCR = destroyed 
If T cells recognise MHC = +Ve selection
If T cells rect too strongly with self antigen = -ve selection
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12
Q

What is peripheral tolerance

A

Monitoring of lymphocytes within secondary lymphoid organs and circulation
Regulatory T cells destroy self-reactive lymphocytes - CD4 + CD8
Prevent overactivity and suppress immune response

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13
Q

What do cytotoxic T cells do (CD8) when activated (when APC presents MHC1)

A

Release IFN-Y and TNFa - direct anti-viral and anti-tumour
Release cytotoxic granules (perforin and granzyme) similar to NK
Apoptosis by Fas
Programmed cell death
Complement activation
Recruit B cells

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14
Q

How do they work

A

Host cell expressing MHC1 which shows virus

Recognised by TCR on T cell

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15
Q

What do T helper cells do (CD4)

A

When CD4 activated differentiate into different T helper cells which release different cytokines
Release cytokines to help other immune
Promote B cell Ab class switching - IgM to IgG
Maxomise phagocyte activity by activating macrophages
Activate CD8 T cells

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16
Q

What is role of Th1

A 
Respond to intracellular pathogen
Maximise MO and CD8
Release IFN-Y
Stimulate B cells to produce IgG
Activate CD8 
Inhibit Th2
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17
Q

What is role of Th2

A

Respond to extracellulair pathogens
Release IL
Activate mast cell, basophil and eosinophil
Stimulate B cells to produce all Ab but particularly IgE
Class switch to IgE
Inhibit Th1

18
Q

What is role of Th17

A

Respond extracellular
Pro-inflammatory
Recruit neutrophil and MO via CXCL-8

19
Q

What does overactivity of Th1 lead too

A

Type IV hypersensitivity

20
Q

What does overactivity of Th2 lead too

A

Type 1 hypersensitivity e.g. asthma

21
Q

What does overactivity of TH17 lead too

A

Pro-inflammatory state in autoimmune e.g. RA

22
Q

What does humeral immune system involve

A

B cells + Ab

23
Q

What is an antibody / Immunoglobulin

A

Glycoprotein produced by plasma cells of B lymphocyte that bind to antigen with high degree of specificity

24
Q

What makes up antibody

A

2 Heavy chain (Fc region)

2 Light chain (FAB region)

25
Q

What does FAB region do

A

Binds to antigen receptors
Can be kappa or lamba
Variable to bind to different. types
Every single clone of B cell should have different variable region

26
Q

What does Fc region do

A

Binds to immune cells to activate

Constant region and determines type of Ab - IgG / IgM etc which all have different roles

27
Q

Role of IgM

A 
Primary response 
Best at activating complement 
Cold Ab often IgM = haemolysis
Produced as fetus
Don't pass to foetal circulation so can cause haeomylsis
28
Q

Role of IgG

A 
Secondary response 
Don't produce till born so crosses placenta
Enhance phagocytosis
Fixes complement
Most abundant in serum
29
Q

Role of IgA

A

Present in secretions
Most predominant in breast milk + other tracts
Localised protection on mucous membrane
Not produced till 1-2 months

30
Q

Role of IgE

A

Parasitic infection + allergy
Mediates type 1 hypersensitivity
Bind to Fc receptors on mast cell and basophil
Least abundant

31
Q

Role of IgG

A

Unknown

32
Q

What occurs in Ab mediated immunity

A

Foreign antigen
Lag phase whilst activate B cell differentiate into plasma
Rely on innate
Low volume of IgM Ab released
Memory B cells also produced to remember antigen
If encountered again memory B cells quickly produce plasma cells = release of high volume of IgM and IgG

33
Q

What is class switching

A

IgM - IgG

Requires stimulation by CD4 T cell

34
Q

How are B cells activated

A

B cell recognise antigen direct via BCR (Ab)
Naive B cell and BCR (Ab) comes into contact with antigen
Each B cell only has one Ab specific to one antigen
B cell process antigen and present it with MHC II
MHC II binds to T helper in secondary lymphoid
Activates B cell
Can also be activated directly by antigens without T cell
Once activated develop into plasma cell or memory B cell (occurs in germinal centre of LN, spleen and MALT)

35
Q

What are functions of Ab

A 
Immune complex
Opsonisation
Activating complement by classic pathway 
Agglutination by directly attaching 
ADCC
36
Q

What is ADCC

A

Ab dependent cellular cytotoxicity

Ab binds to target cells + initiates non-phagocytic cell mediated destruction e.g. by NK cell or granulocytes

37
Q

When does immune system vary

A

Neonates
Elderly
Pregnancy

38
Q

What affects elderly

A

Fewer T cells so dependent on memory
Thyic involution
Reduced B cell develpment
More dependent on innate

39
Q

Main action of Ab

A 
Agglutination
Neutralisation
Oppsonisation
Complement activation
Degranulation
Cell mediated cytotoxicity
40
Q

What happens in passive immunity

A

Administration of pre-form Ab if exposed to high risk

No long term

41
Q

Where do you get it

A

Pooled from human donor in blood transfusion

42
Q

What happens in active

A 
Administer pathogen or component
Taken up by ABC
Present on MHC II to T cell
Activates B cell
Long term immunity

Immunology (7 decks)

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