The human immune system A simplified account of how your immune system works.
-
Upload
diana-cobb -
Category
Documents
-
view
238 -
download
1
Transcript of The human immune system A simplified account of how your immune system works.
![Page 1: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/1.jpg)
The human immune system
A simplified account of how your immune system works
![Page 2: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/2.jpg)
The immune response
starts with an antigen
approaching a cell of
the immune system,
here a macrophage.
antigen
macrophage
The Humoral Response - Activation Phase
![Page 3: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/3.jpg)
The macrophage
engulfs the antigen
by phagocytosis. Lysosome containing enzymes
Antigen engulfed in vesicle
![Page 4: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/4.jpg)
The vesicle containing an
antigen fuses with a
lysosome. The enzymes in the
lysozome break down the
antigen into fragments. This is
antigen processing.
antigen processing
![Page 5: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/5.jpg)
Inside the macrophage,
the processed antigens
combine with special
class II MHC proteins.
These proteins can
move to the cell surface
membrane.
enzymes andproteins combining
Class IIMHC proteins
![Page 6: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/6.jpg)
The antigen/MHC protein
complex is displayed on the
immune cell surface
membrane. The
macrophage is now known
as an antigen presenting
cell.
Processed antigen/MHC protein complex
Antigen-presenting cell
![Page 7: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/7.jpg)
The next stage involves a helper T cell
(also know as a T-helper cell) as well as
the macrophage
T helper cell (TH)
macrophage (antigen-presenting cell)
receptors which bind to specificantigen/MHC protein complex
![Page 8: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/8.jpg)
The receptors on the helper T cell enable
it to bind to the specific antigen-MHC
complex of the antigen presenting cell.
macrophage (antigen-presenting cell)
helper T cell
![Page 9: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/9.jpg)
The binding of the helper T cell with the
antigen - MHC protein complex triggers the
macrophage to release proteins (cytokines)
that activate the helper T cell.
Cytokines from macrophage
![Page 10: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/10.jpg)
The activated helper T cell now releases its own cytokines
Cytokines from helper T cell
![Page 11: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/11.jpg)
The released cytokines stimulate the
helper T cell to reproduce and form a
clone of cells. Each new cell has the same
receptors as the original helper T cell, so
they are specific for the original antigen.
Clone of helper T cells
![Page 12: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/12.jpg)
Another phase of the immune
response begins with a B cell.
The B cell has membrane
bound globular receptor
proteins (called IgM). Some of
these are specific for the same
antigen presented earlier by
the antigen presenting cell.
The Humoral Response - Effector Phase
antigen
B cell
IgM receptor
![Page 13: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/13.jpg)
The B cell’s receptor
protein (an IgM) binds to
the antigen, and the cell
engulfs the antigen by
endocytosis.
IgM bound to antigen engulfed by cell
lysosome
![Page 14: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/14.jpg)
The vesicle formed
inside the B cell fuses
with a lysosome. This
contains digestive
enzymes which break
down the antigen.
Fused vesicles containing antigen and enzymes from lysosome
B cell
![Page 15: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/15.jpg)
Fragments of the
digested antigen
remain after
processing within the
vesicle.
Processed antigen
Class IIMHCprotein
![Page 16: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/16.jpg)
The processed antigen
is attached to Class II
MHC receptors within
the B cell, and is
transported to the
membrane.
![Page 17: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/17.jpg)
The MHC proteins form
a complex with the
antigen which is
displayed on the surface
of the B cell. It has
become another type of
antigen presenting cell
Antigen/MHC protein complex
B cell (antigen presenting cell)
![Page 18: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/18.jpg)
A helper T cell from the clone of cells produced earlier specifically recognises the antigen presented by the B cell.
Antigen-presenting B cell
Helper T cell clone
![Page 19: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/19.jpg)
The helper T cell cell binds to the antigen/MHC
protein complex displayed by the B cell.
This triggers the release of cytokines from the T cell.
Once the cytokines are released the helper T cell no
longer binds to the B cell.
Cytokines released by helper T cell
helper T cell binds to antigen complex on B cell
![Page 20: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/20.jpg)
The cytokines released by the helper T
cell stimulate the B cell to divide and form
a clone of identical cells
B cell clones
![Page 21: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/21.jpg)
The B cells continue to
divide and form two
groups of clones. Some
are long – lived MEMORY
cells. Most are antibody-
secreting PLASMA cells.
Plasma cells have
extensive endoplasmic
reticulum and many
ribosomes.
Memorycell
Plasma cells
![Page 22: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/22.jpg)
Plasma cells are essentially antibody factories. They produce and secrete antibodies identical to those of the surface receptors of the original parent B cell
antibodies
![Page 23: The human immune system A simplified account of how your immune system works.](https://reader033.fdocuments.us/reader033/viewer/2022061609/56649ce55503460f949b2539/html5/thumbnails/23.jpg)
Like the IgM surface receptors on the parent B cell,
the antibodies can bind to and inactivate the
antigens, forming an antibody-antigen complex.
This complex makes it easier for other white blood
cells to engulf the antigen (phagocytosis).
Antibody-antigen complex