THEME 8: INFECTION + IMMUNODEFICIENCY’S
Adhesion, colonizaton, invasion establishment of focus of infecton
Immune response against microbes
the pathogens are specialized in their tricks to infects a human or the animal. They evoke very distnct
immune responses.
Survival + pathogenicity of microbes is infuencee by their ability to evaee or resist efector
mechanisms
But: there are a lot of microorganism.
Specialized immune response
IMMUNITY TO EXTRACELLULAR BACTERIA
We neee: phagocytes, complement, antboeies, B-cell, CD4 T-cells to clear extracellular proliferatng
bacteria.
Things you need in the innate immune system to fght the pathogen:
Complement actvaton: alternatve pathway is actve in the innate immune system which makes
phagocytosis easier, lectn pathway.
You need enhancement of phagocytosis and producton of pro-infammatory cytokines
Aeaptve immunity to extracellular bacteria:
Antbodies can induce:
neutralizaton > prevent adhesion to epithelial surfaces
Opsonizaton > important for take up by phagocytes by Fc receptor-mediated phagocytosis.
Complement actvaton> bacteria can be coated with antbodies and complement factors, these
pathogens can be recognized and destroyed, infammaton, or lysis of the microbe
Cellular part:
DC presents bacteria and present to CD4+ Helper cell:
IL-17,TNF, other cytokines infammaton
TH1 cells which stmulate macrophages for phagocytosis by IFN-y
various cytokines
The immune response can also cause harm to your own tssue
Yellow = antgen which is able to bind on the outside of the T-cell receptor and MHC. The antgen can
actvate the specifc T-cell > leads to a high amount of T-cell actvaton, lots of cytokines > harm to the
, tssue.
Superantgens can cause cytokine storm
Escape strategies from bacteria
The bacteria have all kinds of trades that they use to escape the
immune system:
Example) Neisseria has multple tricks:
proeuces IgA proteases > cut a part of the IgA, IgA can stll bound the
bacteria but isn’t recognized by the immune system anymore.
It produces pili > they build up their pili with diferent genes, they can
chance their proteins all the tme.
sialylaton of LPS > avoid recogniton by complement system
chance surface antgens over tme > they have ways to produce
diferent proteins
Decoy membrane blebs > distract the immune system, the immune
system focusses on the blebs and not on the pathogen itself.
Polysacchariee encapsulatee bacteria are resistant to phagocytosis.
Conjugate vaccines
More enhanced immune response to fght polysaccharide encapsulated bacteria: Receptor on B-cell is
specifc for the Polysaccharide. It will take up and present the polysaccharide and this way can actvate
the T-cells.
IMMUNITY TO INTRACELLULAR BACTERIA
We neee NK cells, T-cells ane IFN-y to clear proliferatng intracellular bacteria
Figure: T cell defense against intracellular bacteria
2
Adhesion, colonizaton, invasion establishment of focus of infecton
Immune response against microbes
the pathogens are specialized in their tricks to infects a human or the animal. They evoke very distnct
immune responses.
Survival + pathogenicity of microbes is infuencee by their ability to evaee or resist efector
mechanisms
But: there are a lot of microorganism.
Specialized immune response
IMMUNITY TO EXTRACELLULAR BACTERIA
We neee: phagocytes, complement, antboeies, B-cell, CD4 T-cells to clear extracellular proliferatng
bacteria.
Things you need in the innate immune system to fght the pathogen:
Complement actvaton: alternatve pathway is actve in the innate immune system which makes
phagocytosis easier, lectn pathway.
You need enhancement of phagocytosis and producton of pro-infammatory cytokines
Aeaptve immunity to extracellular bacteria:
Antbodies can induce:
neutralizaton > prevent adhesion to epithelial surfaces
Opsonizaton > important for take up by phagocytes by Fc receptor-mediated phagocytosis.
Complement actvaton> bacteria can be coated with antbodies and complement factors, these
pathogens can be recognized and destroyed, infammaton, or lysis of the microbe
Cellular part:
DC presents bacteria and present to CD4+ Helper cell:
IL-17,TNF, other cytokines infammaton
TH1 cells which stmulate macrophages for phagocytosis by IFN-y
various cytokines
The immune response can also cause harm to your own tssue
Yellow = antgen which is able to bind on the outside of the T-cell receptor and MHC. The antgen can
actvate the specifc T-cell > leads to a high amount of T-cell actvaton, lots of cytokines > harm to the
, tssue.
Superantgens can cause cytokine storm
Escape strategies from bacteria
The bacteria have all kinds of trades that they use to escape the
immune system:
Example) Neisseria has multple tricks:
proeuces IgA proteases > cut a part of the IgA, IgA can stll bound the
bacteria but isn’t recognized by the immune system anymore.
It produces pili > they build up their pili with diferent genes, they can
chance their proteins all the tme.
sialylaton of LPS > avoid recogniton by complement system
chance surface antgens over tme > they have ways to produce
diferent proteins
Decoy membrane blebs > distract the immune system, the immune
system focusses on the blebs and not on the pathogen itself.
Polysacchariee encapsulatee bacteria are resistant to phagocytosis.
Conjugate vaccines
More enhanced immune response to fght polysaccharide encapsulated bacteria: Receptor on B-cell is
specifc for the Polysaccharide. It will take up and present the polysaccharide and this way can actvate
the T-cells.
IMMUNITY TO INTRACELLULAR BACTERIA
We neee NK cells, T-cells ane IFN-y to clear proliferatng intracellular bacteria
Figure: T cell defense against intracellular bacteria
2
