Post on 18-Dec-2015
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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)
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