Immunology Chapter 11 – Immunological memory and vaccination
Primary and secondary adaptive immune response
Primary adaptive immune response: naïve T cells
do not know what to do with the infections. When the T cell see the antigen in the
context of MHC presented by DCs they become activated (3 signals):
Effector cells (short lived, help clear active infection) (antigen dependent)
o Effector T cell
o Effector B cell = Antibody --> short lived
plasma cell
Memory T and B cells (long lived, prevent re-
infection) (antigen independent)
(1 or 2 weeks)
Protective immunity: effector T cells goes down but antibody (short-lived plasma
cell) specific against pathogen is still in the blood and gives protective immunity (2 or
3 months – seasonal protection against e.g. influenza due to neutralizing IgG and
IgA)
Immunological memory: (1 or 2 years)
Memory T cells
Memory B cells
Long-lived antibody level slowly decreases but stay at certain level
--> Ensures protection upon re-infection with previously encountered pathogen.
For pathogens with a high mutational load (during their
lifetime and during their expansion these pathogens
constantly gain mutations) the Im is not always sufficient
(e.g. influenza virus uses the inhibitor ability of high
affinity IgG)
- During the first infection the influenza virus has 4
different epitopes
- During the second infection the influenza virus has
changed due to mutations the surface expression of the different epitopes. It
now has 3 different epitopes which are all changed
- During the third infection the influenza virus has changed due to mutations the
surface expression of the different epitopes. It now has 2 different epitopes
which are all changed
- During the fourth infection the influenza virus has changed due to mutations
the surface expression of the different epitopes. It now has 1 different epitope
which are all changed
- During the fifth infection the influenza virus has changed due to mutations the
surface expression of the different epitopes. New epitopes are presented – no
longer high affinity IgG available
Secondary adaptive immune response: when the pathogen load increases compared
to immunological memory a secondary immune response is required.
, Memory cells know what to do with the infections and directly activate the effector
cells (only signal 1)
It is faster, stronger and higher affinity because:
1. Pathogen-specific memory cells outnumber naïve cells
2. Memory cells are more rapidly activated compared to naïve cells: because
they have only to undergo signal 1 and not signal 2 and 3 --> faster
3. Memory B cells already undergo isotype switching to generate production of
high affinity IgG/IgA/IgE + during secondary response naïve B cells are
inhibited and this inhibit formation of low affinity
antibodies --> stronger & higher affinity
During primary response naïve B cells become:
Plasma cells with low affinity IgM
Form a germinal centre with T cells
o Memory B cells
o High affinity plasma cells IgG, IgA and
IgE
During secondary response we already have the memory B cells which are
10-100x more pathogen-specific than naïve B cells. The memory B cells:
Undergo isotype switching to generate high affinity plasma cells IgG,
IgA and IgE
Will form a new germinal centre and undergo affinity maturation:
somatic hypermutation and again isotype switch. They differentiated in
even higher affinity plasma cells IgG, IgA and IgE
Inhibition of naïve B cells is initiated via activation of the inhibitor receptor
FcyRIII --> FcyRIII bind to IgG --> initiated inhibitory signals to naïve B cells -->
no production of low affinity antibodies
Affinity and amount of IgG goes up during each infection round
(3 or 4 years)
Memory B and T cell
They provide protection against pathogens for long time due to existence
of a steady memory cell pool: Memory cells see the cytokines IL-7 and IL-
15 --> memory cells divide --> go to the quiescent pool, some die of
apoptosis and these will be replenished by the dividing memory cells
B cells
Memory B cells can be distinguished from naïve and effector B cells:
Membrane bound vs secreted immunoglobulin
Membrane receptor IgG vs membrane receptor IgM and IgG
Round morphology vs different morphology with more intracellular
compartment
Primary and secondary adaptive immune response
Primary adaptive immune response: naïve T cells
do not know what to do with the infections. When the T cell see the antigen in the
context of MHC presented by DCs they become activated (3 signals):
Effector cells (short lived, help clear active infection) (antigen dependent)
o Effector T cell
o Effector B cell = Antibody --> short lived
plasma cell
Memory T and B cells (long lived, prevent re-
infection) (antigen independent)
(1 or 2 weeks)
Protective immunity: effector T cells goes down but antibody (short-lived plasma
cell) specific against pathogen is still in the blood and gives protective immunity (2 or
3 months – seasonal protection against e.g. influenza due to neutralizing IgG and
IgA)
Immunological memory: (1 or 2 years)
Memory T cells
Memory B cells
Long-lived antibody level slowly decreases but stay at certain level
--> Ensures protection upon re-infection with previously encountered pathogen.
For pathogens with a high mutational load (during their
lifetime and during their expansion these pathogens
constantly gain mutations) the Im is not always sufficient
(e.g. influenza virus uses the inhibitor ability of high
affinity IgG)
- During the first infection the influenza virus has 4
different epitopes
- During the second infection the influenza virus has
changed due to mutations the surface expression of the different epitopes. It
now has 3 different epitopes which are all changed
- During the third infection the influenza virus has changed due to mutations the
surface expression of the different epitopes. It now has 2 different epitopes
which are all changed
- During the fourth infection the influenza virus has changed due to mutations
the surface expression of the different epitopes. It now has 1 different epitope
which are all changed
- During the fifth infection the influenza virus has changed due to mutations the
surface expression of the different epitopes. New epitopes are presented – no
longer high affinity IgG available
Secondary adaptive immune response: when the pathogen load increases compared
to immunological memory a secondary immune response is required.
, Memory cells know what to do with the infections and directly activate the effector
cells (only signal 1)
It is faster, stronger and higher affinity because:
1. Pathogen-specific memory cells outnumber naïve cells
2. Memory cells are more rapidly activated compared to naïve cells: because
they have only to undergo signal 1 and not signal 2 and 3 --> faster
3. Memory B cells already undergo isotype switching to generate production of
high affinity IgG/IgA/IgE + during secondary response naïve B cells are
inhibited and this inhibit formation of low affinity
antibodies --> stronger & higher affinity
During primary response naïve B cells become:
Plasma cells with low affinity IgM
Form a germinal centre with T cells
o Memory B cells
o High affinity plasma cells IgG, IgA and
IgE
During secondary response we already have the memory B cells which are
10-100x more pathogen-specific than naïve B cells. The memory B cells:
Undergo isotype switching to generate high affinity plasma cells IgG,
IgA and IgE
Will form a new germinal centre and undergo affinity maturation:
somatic hypermutation and again isotype switch. They differentiated in
even higher affinity plasma cells IgG, IgA and IgE
Inhibition of naïve B cells is initiated via activation of the inhibitor receptor
FcyRIII --> FcyRIII bind to IgG --> initiated inhibitory signals to naïve B cells -->
no production of low affinity antibodies
Affinity and amount of IgG goes up during each infection round
(3 or 4 years)
Memory B and T cell
They provide protection against pathogens for long time due to existence
of a steady memory cell pool: Memory cells see the cytokines IL-7 and IL-
15 --> memory cells divide --> go to the quiescent pool, some die of
apoptosis and these will be replenished by the dividing memory cells
B cells
Memory B cells can be distinguished from naïve and effector B cells:
Membrane bound vs secreted immunoglobulin
Membrane receptor IgG vs membrane receptor IgM and IgG
Round morphology vs different morphology with more intracellular
compartment
