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The Fish
Immune
System
What does the
immune system do?
War
Fish vs. Everything
Enemy Pathogens
Front Lines
Self
The good bits
that are
supposed to
be there
Foreign
The bad stuff:
bacteria,
fungi, viruses,
cancer
Planes, Ships Tanks,
and Ammunition
• (Planes, Ships, Tanks) White blood cells
–
–
–
–
Lymphocytes
Neutrophils
Macrophages
Eosinophils
• (Mines and Booby Traps) Blood Proteins
–
–
–
–
Complement
Lysozyme
Antibodies
Many more
Inside the Liver
“Gee Adjwoa, I
really like the
bling on your cell
phone”
Complement
A defensive protein
made by the liver and
secreted into the
blood. Primary target:
Gram negative
bacteria.
Gram Neg
Gram Pos
Membrane bi-layer
Peptidoglycan layer
Complement
molecules begin
to assemble a
complex on the
membrane of
Gram (-) bacteria
Complement
forms a channel
through the cell
wall
Complement
Recognizes
Gram (-)
bacteria
Lysozyme
Lysozyme
• Dissolves Gram (+)
bacterial cell walls
• Found in
– Blood
– Mucus
– Eggs
Other Mines….
•
•
•
•
Proteases: Damage pathogens
Protease inhibitors: Block invasion
Histones: Antibacterial
Iron-sequestering proteins: Starve
bacteria.
• Lactoferrin disrupts outer
membrane on Gram negs (helps
lysozyme)
• C-reactive protein: Recognizes
bacteria, triggers complement
Mines
• Blood Proteins
• Always there and ready
• Work in complexes
• Identify foreigners
• Destroy or disable
Lymphocyte
Antibodies
Antibodies: Blood
proteins that bind to
foreigners. Made by
lymphocytes
Antibody Anatomy
Variable
Binding
Region
Antibody Molecule
Antibodies bind all over a
Rhabdovirus and block it from
infecting a cell.
Antibodies recognize foreign antigens on an
“ich” parasite and mark it for destruction.
Antibodies
Designate Targets
Location of the
Thymus in a Grass
Carp
Life and Death
in the Thymus
“Lymphocyte
Must Die”
Thymocyte
Self Antigen
Antigen
More
Identical
B-Cells
Memory
Cell
B-Cell
Plasma cell
Memory cells: The Lymphocyte Barracks
T-Lymphocyte
Viral
Proteins
(antigens)
Cell Killing
Chemicals from
the T-cell
Virus-infected cell
Antigen
T-Cell
More
Identical
T-Cells
Memory
Cell
Memory cells: The Lymphocyte Barracks
B-cells: Secrete
antibodies that bind to
antigens on foreign
things
T-cells: Attach to
and kill infected
cells with foreign
antigens
Lymphology
• Self reacting lymphocytes
weeded out by thymus
• Lymphocytes proven useful
proliferate to make more highly
trained fighter pilots (B&T), and…
• Copies of useful lymphocytes are
put in the barracks in case the
same enemy attacks again.
Macrophages
“Big Eaters"
Macrophage
Macrophages as
Big Eaters
Macrophage
Diets
Bacterial Cell Walls
Cell with Compliment
Cells with Antibody Flags
Vacuoles
containing
bleach (brown)
and peroxide
(green) fuse
with a vacuole
containing a
live bacterium
More Tricks:
Macrophages
Searching out
Foreigners
A roving macrophage detects a
parasite trying to hide among a
layer of fish cells.
Normal cells with MHC “locks”
Parasite with fake lock
Macrophages
Even Run a
School for
Lymphocytes
2
1
Macrophage
3
Macrophage eating a bacterium
4
Macrophage digesting
a bacterium
Macrophage using
bacterial bits to
educate lymphocytes.
Macrophage
Functions
• Eat and kill bad cells
• Check cell codes (MHC)
• Run a lymphocyte
school
Eosinophils
Eosinophils
Eosinophils
The worm
has been
“flagged” by
antibody
molecules
The eosinophil dumps parasitekilling chemicals on a parasitic
worm somewhere inside of a fish.
Neutrophils
Neutrophils
Neutrophils
•Dump
toxins on
flagged
cells
(chemical weapons!)
Neutrophils
Mediate immune
responses
Other Tanks and
Planes
•Neutrophils:
Chemical warfare,
generals
•Eosinophils: Chemical
warfare on parasites
Natural Killer Cells (NK)
Foreign cells
Virus infected cells
Protozoa
Armed Checkpoints
The
Spleen