Immunology NON-SPECIFIC RESPONSES – SPECIFIC RESPONSES –

Immune System and Response – Immune Response –

Immune systems Parts of the system (systemic) – Mucosal immune system –

Non-specific immune system Very Important in fish Logical, due to aquatic environment –

Surface Barriers in Fish Fish Skin, and Scales – Mucus – Lysosymes – act on microorganisms –

phagosome forming lysosome damage and digestion phagocytosis lysosome fusion Release of microbial products Phagocytosis

Body fluid Barriers Complement – Transferrin – Interferon –

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 phagocytebacteria 1. lysis 2. chemotaxix 3. opsonization

Immune System Cells Phagocytes- – –neutrophils Natural killer cells –

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 IgM IgA IgE IgD IgG Mammals Fish Plasma Cell Spleen Liver Ant. Kidney Thymus T cell B cell Macrophage with antigen Activated T cell Cell mediated Immunity Humoral Immunity stem cell Memory Cell

Antigen Presentation Resting T-cell Activated T-cell Accessory cell B-cell Ig synthesis antigen B cell epitope T cell epitope MHC CD4 CD3 TCR Activation IL-1 signal IL-2, IL-4 IL-4, IL-5

Antibodies (Immunoglobulin) in fish Binding sites Bacteria or virus

Clonal Selection Antigen selection B cells Proliferation/ maturation Plasma cells Memory cells Production of antibody 2

Memory Antibody Memory Immune response Primary vaccination Time Natural infection or booster Primary and secondary response

Antibodies Protein or Antigen – 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 –

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 Ab synthesis IgMIgG/YIgAIgDIgE Mammals Birds Reptiles ? Frogs/toads Salamanders /newts Lungfish Teleost fish ? Sharks/rays Jawless fish

Vaccination Many vaccines have non-specific adjuvant that results in release of interleukines/cytokines and stimulatory factors

Anamestic Response Primary response – Cell mediated immunity Secondary Response –

Factors Affecting Immune Response Intrinsic Fish – Extrinsic factors - –