The Immune Response

The 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.

The LYMPHATIC SYSTEM• lymph capillaries lymph vessels lymph 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)

The LYMPHATIC SYSTEM

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 on infection

• Immune response

Lymphoid 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 response

1. 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 Tissue• B and T cells are lymphocytes

formed in red bone marrow but mature in two diff. places• B cells: bone marrow• T cells: Thymus

The Immune ResponseAntigens:•Generally

-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

The Immune Response

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 / lymph

The Immune ResponseAntibodies can:

- Combine and inactivate the antigen by inhibiting the reactions with other cells (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)

The Immune Response• 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.

The Immune Response• 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: Become a specialised T Cell4. Some become memory cells and spread

out to all body tissues Allows faster response in future.

The Immune ResponseKiller T Cells

- Attach to antigen and destroy it Helper T Cells

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

Suppressor T Cells

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

The Immune Response

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 manufactures antibodies in defence• Natural (actually infected) or artificial

(injection)• Long lasting

Types of ImmunityVaccines• Vaccination: Artificial Active Immunity. (Antigen

introduced individual produces antibody doesn’t suffer symptoms)

• 4 Main vaccine types:1. Micro-organisms/Viruses of reduced 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, tetanus

4. Sub-unit Vaccine: fragment of organism• e.g. Hep B

• Delivery: syringe, ingested, nasal spray, skin patches,

Types of ImmunityRisks• Allergic reaction• Possible cross-species disease introduction

(while immunising an individual it is possible that the vaccine also contains strains on another infectious disease as a result of the cultural medium it was developed in)

• Preservatives?

Types of ImmunityEthical 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)• Animal testing on: mice (other

mammals), fish, amphibians, birds