Download Non specific defense mechanisms of fish

The non-specific defense
mechanisms of fish
By Andrew G Challingsworth
The non-specific defense
mechanisms of fish
• The organism needs to defend itself not
only from pathogens that are outside the
body, such as bacteria, viruses etc but also
from abnormal cells within the body which
can give rise to cancers.
Two defense systems have
evolved in this respect.
• 1) The non-specific defense mechanism
which we will take a closer look at in this
short study.
• 2) The specific defense mechanism or the
immune system.
Non-specific defense mechanism
or the innate immune system.
• Much published work on the innate immune
system in recent years.
• In reference too!
• 1)Disease resistance
• 2)Prophylactic measures
• 3)Environmental changes
• 4)Genetic trait
Recent Publication cont!
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5)activity of macrophages
6)Cytotoxic cells
7)Complement components
8)Interferon
9)antibacterial peptides
10)Immunostimulants
11)Immunostimulants application
Non-specific defense
mechanisms or the innate
immune system!
• Phylogenetically ancient mechanisms.
• Block entry of pathogens into the body.
• Eliminate them in a non-specific fashion.
Included in this category!
• Acute phase proteins
• I.e. C-reactive proteins
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Pentraxins C-reactive proteins (CRP) and
Serum amyloid protein (SAP) are lectins.
Present in the body fluids of vertebrates.
Commonly associated with acute phase response.
Following significantly increased
serum levels!
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Following tissue injury
Trauma
Infection (The acute phase response)
Pentraxins take part in innate immune
defense. Lectin type binding role.
• Activate the complement pathways
recognition and clearance of apoptotic cells.
Includes two lines of defense!
• First line of defense is external.
• Consisting of the skin, scales, and mucous
membranes also secretions produced by
fish.
• Second line of defense is internal.
• Triggered by chemical signals, employs
antimicrobial proteins and phagocytic cells
and the inflammatory response.
First line of defense Skin and
mucous membranes!
• Skin provides barrier that cannot be
penetrated by bacteria or viruses.
• But small abrasions can allow passage.
• Mucous membranes lining the digestive,
respiratory and urinogenital canals act as:
• Barrier to microbes and is an effective nonspecific defense.
Fish mucous contains immune
parameters!
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Lectins
Pentraxins
Lysozyme
Complement proteins
Antibacterial peptides
Igm
Limited pathogen recognition machinery
although strength of innate defense against
pathogens is impressive!
• Although sluggish (up to 12 weeks)
• Poiklothermic nature limited antibody repertoire
affinity, maturation and memory.
• slow lymphocyte proliferation.
• Compared to the instant temperature of relatively
independent innate immune response.
• Innate immune system is essential to the function
of acquired immunity and determines the nature of
the acquired response.
Phagocytic white blood cells!
• Phagocytosis ingestion of invading microbes by
white blood cells (WBCs)
• Neutrophils 60-70% of all WBCs amoeboid
movement, destruction of microbes.
• Monocytes 0.5% of (WBCs) stronger phagocytic
response.
• Eosinophils limited phagocytic activity contain
destructive enzymes.
• Natural killer cells destroying infected cells
invaded by virus’s.
Antimicrobial proteins!
• Two important antimicrobial proteins
complement and interferons.
• Complement
• Cooperating proteins several have a
cascading effect, lysing invading pathogens.
• Also act as attractants or chemotaxis to
draw in phagocytes to site of infection.
Interferons (IFN)!
• Substance produced which helps cells resist
virus infection.
• Several types known
• Mass produced by recombinant DNA
techniques.
• Inhibit replication of virus.
• They are not virus specific.
• Found mainly in the serum.
Natural haemolysins!
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Substances found in fish serum.
Small molecular weight
Capable of lysing foreign Red Blood cells.
These chemicals have bactericidal
properties.
Conclusion
• The importance of the non-specific defense
mechanism is protection of the animal
against disease which however varies in
different groups.
• Being highest in invertebrates and lowest in
man however having an intermediate
response in fish is apparent.