What are the non-specific defense mechanisms
- Surface barriers - mucus
- Entraps and sloughs off - inhibiting colonisation
- Mucus production increases in response to infection/inflammation
- Skin
- Epidermis is non-keratinized and nucleated
- Intergirty is vital to maintain osmotic balance and exclude micro organisms
- Healing is rapid even at low temperatures
What does melanin respond to
- Cytokines
What are melanomacrophages
Melanin-producing cells originating from mesenchymal, hematopoietic stem cells
What is hyper-pigmentation
- Non-specific indicator of chronic inflammation and/or poor-doing
A non-specific defense mechanism: the gill
- A very large surface area of delicate epithelium
- Protected by mucus
- Also contains phagocytic cells
A non-specific defense mechanism: GIT
- Mobile or circulating leukocytes are key cellular components of fish innate defense mechanism
- Monocytes, granulocytes, thrombocytes and non-specific cytotoxic cells
- Less mobile tissue granulocytes, eosinophilic granular cells, provoke immune defence against bacteria and parasitic worms at mucosal sites
- Leukocytes are not antigen-specific
- Cells possess pattern recognition proteins or receptors to recognise pathogens associated molecular patterns
Name the phagocytes
- Monocytes
- Neutrophil
- B cells in fish
Where are the macrophages located
- Gills, body cavity, mainly as RES cells in the kidney and spleen and cardiac atrium
- Monocytes found in the kidney and small numbers in blood
- Macrophages that contain mealnin - melano-macropahges
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What contains neutrophils
- Kidney, spleen, blood and inflammatory lesions
How is inflammation induced
H2O2 vasoactive amines, complement, eicosanoids and cytokines which are released in response to tissue damage or products of pathogens
What immunoglobin do fish lack
IgA
What is memory specific to
- Ag
- They have no obvious class switching
- Temperature dependent
- Establishment of memory also takes longer duration
What are the factors affecting the immune response
- Extrinsic - environement and nature of antigen
- Intinsic - regulatory mechanisms within the immune system
- Physiological state of the animals including ontogenic factors
What is the protection layer in crustaceans
Cuticles
What do crustacenas lack
Immunoglobulins and complement factors
What are hemocytes
- Antimicrobial peptides are major components involced in the defense mechanism of a wide range of organsisms, mainly exhibiting a broad spectrum of activites against G(+ve) and G(-) fungi and bacteria and viruses and are promarily expressed in circulating hemocytes - the main site for immune response
- Crustacean hemocytes can innately recognize invading microbes by the engagement of host pattern recognition proteins with pathogen-associated molecular patterns
- The humoral responses are mediated by molecules in haemolymp - the important humoral responses are melanin synthesis by the prophenoloxidase system, the blood clottign system and the generation of circulating antimicrobial peptides
What do hemocytes carry out the functions of
Both red and white blood cells
What are the three different subdivisions of hemocytes
- Hyaline
- Semi-granular
- Granular cells
What are crustacean hyaline hemocytes involved in
Coagulation, encapsulation and nodulation of pathogens
When does the humoral response arise
- When the extracellular signal molecules from pathogens, such as the PAMPs or the viral protein antigens are detected by the cell-surface receptors or PRPs resulting in the activation of signaling pathways
