Chapter 1: Elements of the immune system and their roles in
defense
What is immunology?
• Immunology is the study of physiological mechanisms that humans and other
animals use to defend their bodies from invasion by other organisms.
• The host (the one affected) invests heavily in cells dedicated to defense, which
collectively form the immune system. The immune response costs a lot of
energy.
o There are a lot of different immune cells. But they don’t live very long.
You need to continuously make these immune cells.
Innate cells
Lymphoid cells
• Don’t work on their own, need help
from innate cells.
• 2 different type of T-cells:
o CD4 T-cells (helper T-cells).
o CD8 T-cells (killer T-cells).
• ILC = innate like lymphoid cells.
,The adaptive immune system consists mostly of B-cells and T-cells. The innate
immune system are cells that do not have specific receptors.
Not all the species have adaptive immune responses (= no lymphocytes, only innate
immune system)
• Depends on life time and how soon you can have your offspring.
o Insects can get offspring very quickly, so they need to invest their
energy in that, instead of their immune system.
Innate immunity is more important than adaptive immunity
What does the innate immunity do?
• Skin is also a part of the immune system.
• If the skin is getting destroyed, bacteria can get in.
• The innate cells that are always there starts fighting this bacteria and produces
a lot of cytokines. A signal will be send to the blood vessels. Blood vessels will
open up, so more immune cells can come to the place. They can get rid of the
, bacteria. The innate cells will stay there for a while, because they need to
make sure the damage is repaired.
• If the innate cells cannot manage to get rid of the bacteria, the adaptive
immune system will get activated.
Adaptive immunity: cytotoxic T-cells
• If a healthy cell is infected, then it produces a lot of stress molecules. It
presents peptides (from the pathogen) with the help of MHC molecules.
• The T-cells can recognize the aberrant peptides on the cell surface on the
infected cell and kill them.
T-helper cells
• T-helper cells have different cell surface receptors, therefore they recognize
different MHC molecules.
• When they get activated, they produce a lot of cytokines that help the B-cells
to make antibodies. They also activate the CD8 T-cells.
, B-cells: what do they do?
• They produce antibodies. The antibodies can do:
o Neutralization.
o Opsonization.
• The antibodies can mark the pathogens, so the
pathogens can be more visible to the innate
cells. The innate cells do not have specific
receptors for recognizing pathogens. But they
have receptors for recognizing the Fc part of an
antibody (the constant part).
defense
What is immunology?
• Immunology is the study of physiological mechanisms that humans and other
animals use to defend their bodies from invasion by other organisms.
• The host (the one affected) invests heavily in cells dedicated to defense, which
collectively form the immune system. The immune response costs a lot of
energy.
o There are a lot of different immune cells. But they don’t live very long.
You need to continuously make these immune cells.
Innate cells
Lymphoid cells
• Don’t work on their own, need help
from innate cells.
• 2 different type of T-cells:
o CD4 T-cells (helper T-cells).
o CD8 T-cells (killer T-cells).
• ILC = innate like lymphoid cells.
,The adaptive immune system consists mostly of B-cells and T-cells. The innate
immune system are cells that do not have specific receptors.
Not all the species have adaptive immune responses (= no lymphocytes, only innate
immune system)
• Depends on life time and how soon you can have your offspring.
o Insects can get offspring very quickly, so they need to invest their
energy in that, instead of their immune system.
Innate immunity is more important than adaptive immunity
What does the innate immunity do?
• Skin is also a part of the immune system.
• If the skin is getting destroyed, bacteria can get in.
• The innate cells that are always there starts fighting this bacteria and produces
a lot of cytokines. A signal will be send to the blood vessels. Blood vessels will
open up, so more immune cells can come to the place. They can get rid of the
, bacteria. The innate cells will stay there for a while, because they need to
make sure the damage is repaired.
• If the innate cells cannot manage to get rid of the bacteria, the adaptive
immune system will get activated.
Adaptive immunity: cytotoxic T-cells
• If a healthy cell is infected, then it produces a lot of stress molecules. It
presents peptides (from the pathogen) with the help of MHC molecules.
• The T-cells can recognize the aberrant peptides on the cell surface on the
infected cell and kill them.
T-helper cells
• T-helper cells have different cell surface receptors, therefore they recognize
different MHC molecules.
• When they get activated, they produce a lot of cytokines that help the B-cells
to make antibodies. They also activate the CD8 T-cells.
, B-cells: what do they do?
• They produce antibodies. The antibodies can do:
o Neutralization.
o Opsonization.
• The antibodies can mark the pathogens, so the
pathogens can be more visible to the innate
cells. The innate cells do not have specific
receptors for recognizing pathogens. But they
have receptors for recognizing the Fc part of an
antibody (the constant part).
