Immunology

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• NON-SPECIFIC RESPONSES–

• SPECIFIC RESPONSES– –

Immune System and Response

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• 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– –

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Surface Barriers in Fish• Fish Skin, and Scales

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• 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 phagocyte bacteria

1. lysis 2. chemotaxix 3. opsonization

Immune System Cells

• Phagocytes-

– – – neutrophils

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• 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 circulationMacrophages: Monocytes which have migrated into the tissuesNeutrophils: 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

IgMIgAIgEIgD

IgG

Mammals

FishPlasma

Cell

Spleen

Liver

Ant. KidneyThymus

T cell

B cell

Macrophagewith antigen

ActivatedT cell

Cell mediatedImmunity

HumoralImmunity

stem cell

MemoryCell

Antigen Presentation

Resting T-cell Activated T-cell

Accessory cell

B-cell

Ig synthesis

antigen

B cellepitope

T cellepitope

MHC

CD4 CD3TCR

Activation

IL-1signal

IL-2, IL-4

IL-4, IL-5

Antibodies (Immunoglobulin)in fish

Bindingsites

Bacteria or virus

Clonal Selection

Antigen selection

B cells

Proliferation/maturation

Plasma cells Memory cells

Production ofantibody 2

MemoryAntibody

Antibody

Memory

Imm

un

e re

spon

se

Primary vaccination

Time

Natural infectionor 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 SystemMammals 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

IgM IgG/Y IgA IgD IgE

Mammals

Birds

Reptiles ?Frogs/toads

Salamanders/newts

Lungfish

Teleost fish ?Sharks/rays

Jawless fish

Vaccination

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• 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 –

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Factors Affecting Immune Response

• Intrinsic Fish – – – –

• Extrinsic factors -– – – –