12v2 - Immune Response.docx

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HBS 3AB 11 The Immune Response v2

Lymphatic System

Leucocytes: white blood cells. Some secrete substances which destroy pathogens,others engulf and digest.

Lymphocytes: Approx 20-30% of all white blood cells (mainly T cells and B cells)

Phagocytes: Cells which engulf & digest mirco-organisms / cell debris. Macrophages: develop from some leucocytes. More specific.

lymph capillaries lymph vesselslymph nodes Lymph Nodes:

neck, armpits, groin & around AC

bean shaped (1 25mm) Acts as a filter containing masses of lymphoid tissue (lymphocytes,

macrophages & plasma cells)

Role of Lymphatic System Large particles (e.g. bacteria) trapped in fibre mesh and destroyed by

macrophages via Phagocytosis

Lymphocyte production increases and lymph nodes become swollen oninfection

Immune responseLymphoid Organs

Tonsils: 3 sets in pharynx Spleen: filters blood (like lymph nodes) Thymus: immunity (behind sternum)

The Immune Response

Homeostatic mechanism (very specific)

2 Part immune response1. Humoral response / antibody-mediated immunity

Special proteins (antibodies) produced from B-Cells in Lymphoid Tissue2. Cell mediated response

Special lymphocytes produced from T-Cells in Lymphoid Tissueo B and T cells are lymphocytes formed in red bone marrow but

mature in two diff. places

B cells: bone marrow T cells: Thymus

Antigens: Generally


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- large molecules (proteins carbs, lipids or nucleic acids)- Whole micro organisms (virus particle & bacteria)- Part of a microorganism (cell wall, flagella)- Toxins (from bacteria)- Foreign material

Antibodies: Special Proteins (Immunoglobulins IgA, IgD, IgE, IgG, IgM) made in response to

a non-self antigen

Combines to form an antigen-antibody complex Specific active site (only one specific antigen can combine with any antibody) Released into blood / lymphAntibodies can:

Combine and inactivate the antigen by inhibiting the reactions with othercells (foreign enzyme / bacterial toxin)

Bind to surface, prevent from entering cells (viruses) Coats bacteria, more easily consumed by phagocytes Agglutination (antigens clump together) Dissolve antigen If antigen is soluble, reacts to become insoluble. (easier to be consumed)

Antibody mediated Immunity (B Cells)1. Thousands of diff types of B Cells2. When activated (sensitised) by an antigen, B Cells enlarge and divide clones3. Most clones: plasma cells which secrete a specific antibody4. Some become memory cells and spread out to all body tissues Allows faster

response in future.

Cell mediated Immunity (T Cells)1. Thousands of diff types of T Cells2. When activated (sensitised) by an antigen, T Cells enlarge and divide clones3. Most clones: specialised T Cells4. Some become memory cells and spread out to all body tissues Allows faster

response in future.

Killer T Cells

Attach to antigen and destroy itHelper T Cells

Secretes a substance that sensitises more lymphocytes Secretes a substance that attracts more macrophages Secretes a substance that enhances macrophage activity


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Suppressor T Cells

Release substances that inhibit T and B cell activity, slowing down immuneresponse (when immune response is finished)

Types of Immunity Immunity: resistance to infection by invading micro organisms Immunisation: process of acquiring immunity (Natural or artificial) Passive Immunity: Individual given antibodies produced elsewhere.

Natural (from mother) or artificial (injection) Short lived but fast response

Active Immunity: Individual exposed to foreign antigen the manufacturesantibodies in defence

Natural (actually infected) or artificial (injection) Long lasting

Vaccines Vaccination: Artificial Active Immunity. (Antigen introducedindividual

produces antibodydoesnt suffer symptoms)

4 Main vaccine types:1. Micro-organisms/Viruses ofreduced virulence (attenuated): Decreased

ability to produce disease symptoms (often using recombinant DNA)

e.g. polio, TB, rubella, measles, mumps, yellow fever, flu (nasal spray)2. Dead/Inactivated micro organisms / viruses: not as prolonged

e.g. cholera, typhoid, whooping cough, flu (shot)3. Toxoids: Inactivated toxins from bacteria

e.g. diphtheria, tetanus4. Sub-unit Vaccine: fragment of organism

e.g. Hep B Delivery: syringe, ingested, nasal spray, skin patches,Risks:

Allergic reaction

Possible cross-species disease introduction (while immunising an individual itis possible that the vaccine also contains strains on another infectious disease

as a result of the cultural medium it was developed in)

Preservatives?Ethical Concerns:

How was vaccine manufactured, tested and risks associated? Manufacturing:

animal host tissue (chicken embryos - influenza, mice brains -encephalitis)

human host tissue (aborted foetus rubella) Testing:

May be tested in developing countries (exploited)


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Animal testing on: mice (other mammals), fish, amphibians,birds

12v2 - Immune Response.docx

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