Immunology
• • NON-SPECIFIC RESPONSES
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• SPECIFIC RESPONSES
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Immune System and Response
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• Immune Response
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Immune systems
• Parts of the system (systemic)
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• Mucosal immune system
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Non-specific immune system
• Very Important in fish • Logical, due to aquatic environment
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Surface Barriers in Fish
• Fish Skin, and Scales
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• Mucus
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• Lysosymes – act on microorganisms
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Phagocytosis
phagosome forming lysosome damage and digestion
phagocytosis
lysosome fusion
Release of microbial products
Body fluid Barriers
• Complement
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• Transferrin
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• Interferon
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Signaling (soluble mediators)
Complement (innate/adaptive responses): Group of serum proteins that function in the control of inflammation
“Alternative pathway” (innate): Complement molecules coat microorganism – Acute phase proteins – Spontaneously activated “Classical pathway” (adaptive): Complement molecules activated by antibodies bound to pathogen (cascade)
Cytokines: Group of molecules involved in signalling between cells during immune response
Complement functions
complement
bacteria
1. lysis
phagocyte 2. chemotaxix
bacteria 3. opsonization
Immune System Cells
• Phagocytes– – – neutrophils
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• Natural killer cells
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Immune cells (innate immunity)
Phagocytic Leucocytes (also involved in adaptive responses): Function to engulf particles, including infections agents, internalize and destroy them
Monocytes: Blood cell lineage found in circulation Macrophages: Monocytes which have migrated into the tissues Neutrophils: Ingest and lyse pathogens (lysozyme, acid hydrolases, etc)
Specific Immune System
• Antigen processing by Immunocompetent cells (APC)
– Cellular – Humoral immunity
• soluble antibody
– Lymphocytes “T or B” cells
Specific responses (Adaptive immunity)
Lymphocytes: Initiate adaptive immune responses (derived from stem cells in anterior kidney of fish)
– B-cells: Responsible for producing antibody – T-cells: Cytotoxic functions as well as helper functions for antibody production
Antigen: Any molecule that can be recognized by B and T cells Antibody (Immunoglobulin): Serum proteins that recognize a specific antigen
Immune Response
Ant. Kidney Liver stem cell Macrophage with antigen B cell T cell Thymus
Spleen
Fish IgM
Mammals
IgA IgE IgD
Plasma Cell
Memory Cell
Activated T cell
IgG Humoral
Immunity
Cell mediated Immunity
Antigen Presentation
Resting T-cell Activation
IL-4, IL-5 TCR IL-1 signal CD4
Activated T-cell
IL-2, IL-4
CD3
MHC
B-cell antigen
B cell T cell epitope epitope
Accessory cell
Ig synthesis
Antibodies (Immunoglobulin) in fish
Binding sites
Bacteria or virus
Clonal Selection
Antigen selection B cells
Proliferation/ maturation
Production of antibody 2
Plasma cells
Memory cells
Primary and secondary response
Immune response
Memory
Antibody Memory
Antibody Time Primary vaccination
Natural infection or booster
Antibodies
• Protein or Antigen
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• Structure
Antibody production • T - cells proliferate and release lymphokines, B (memory) cells have different Ig receptors on cell surface that are activated • B cells multiply, release immunoglobins in plasma
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Immune System
Mammals vs Fish
• Mammals – Very advanced leading to long term protection – Ig isotype heterogeneity – Distinct mucosal and systemic (internal) immune systems • Fish – More primitive – shorter duration and less specific – Limited Ig isotype repertoire – Importance of specific mucosal responses not well known
Antibody heterogeneity between vertebrates
Vertebrate group Mammals Birds Reptiles Frogs/toads Salamanders /newts Lungfish Teleost fish Sharks/rays Jawless fish Ab IgM synthesis IgG/Y IgA IgD IgE
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Vaccination
• • Many vaccines have non-specific adjuvant that results in release of interleukines/cytokines and stimulatory factors
Anamestic Response
• Primary response
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• Cell mediated immunity • Secondary Response
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Factors Affecting Immune Response
• Intrinsic Fish
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• Extrinsic factors – – – –