The document contains in-depth, comprehensive notes regarding immunology. Although these are under HUB2021S, they are also helpful in any other course that reviews immunology, such as PTY2001S. At the end of each section, there are learning objectives (questions relating to the previous information...
Immunology
Survival requires immunity
• Full of potential pathogens, 10 commensals per human cell
• Encounter millions of pathogens daily
• Little pathology despite constant exposure
• Immune system constantly dealing with infection and damage
• Immune failure > guaranteed illness (AIDS, chemotherapy, allergies)
• Death > immediate decomposition (tissue acts as rich growth medium for bacteria)
What is immunity?
• Capacity to recognise material as foreign or non-functioning and to neutralise, eliminate
and metabolise them with/ without injury
• Able to differentiate between self and non-self
• Mechanisms allowing recognition of foreign or non-functional structures:
o Innate immunity
o Adaptive immunity
Two arms of the immune system, interactive and inter-dependent
Innate immunity Adaptive immunity
No time lag Lag period
Not antigen specific Antigen specific
No memory Development of memory
Definitions
• Immunology – the study of the immune system or immunity; the study of all aspects of
host defence against infection and or adverse consequences of immune responses
• Immune system – a versatile defence system that has evolved to protect animals from
invading pathogenic microorganisms and cancer
o able to generate a variety of cells and molecules capable of specifically
recognising and eliminating a variety of foreign invaders
o innate: large number of cells
o adaptive: small number of cells but trigger large response
Vaccination – immunological medical intervention
• smallpox vaccine led to eradication of the disease
• ability to control diseases using vaccines
o reduce strain on public health infrastructure
o e.g. polio
o e.g. control of SARS-CoV-2 has been achieved through vaccination
, How is an immune response organised?
• Entry of microbe – has a certain threshold, small entry will not create large response
• Pathogen multiplies > immune system fights back > pathogen levels decrease until
cleared
How does a vaccine work?
• Infections and vaccines induce immunological memory
• Adaptive immune system multiplies, targets specific cells and increases immune
response
• Immune system responds better when you have a prepped immune response
o Faster response during true infection
Learning objectives
- Know examples of why the immune system is important
- What was the first vaccine
- Give examples of diseases effectively controlled by vaccines
- Draw a graph outlining how an immune response develops against a challenge over time
, What can initiate an immune cell response?
1. Secreted molecules from self-cells or pathogens (cytokines)
2. Surface molecules on or shed from self-cells/ pathogens (CD markers)
3. Processed self or foreign antigens (Ag) displaced on self-cells
4. Any biomolecules can act as an antigen; protein, lipid, polysaccharide, combination
• Epitope is recognised by immune system > potential to elicit an immune response
How do external signals affect cells?
• Surface/ internal receptor (lock) > fits cognate ligand (key) > signal transduction >
appropriate cell response
o Antigen, cytokine, antibody > receptor > gene expression
o Cell responses: activation, cytokine secretion, protein synthesis, differentiation,
proliferation, migration, apoptosis
Learning objectives
- What can be an antigen?
- What is an epitope?
- What is a typical cell response following an external signal being recognised by a cell?
- Give examples of molecules that can induce an immune cell response.
- Give examples of immune cell responses.
Innate immunity
• Non-specific – anything seen as foreign/ non-functional is a potential target
• Physical barriers – first line of defence
o Skin, GIT, respiratory tract, nasopharynx, cilia, eyelashes, body hairs
• Physical defence mechanisms – secretion, mucous, bile, gastric acid, saliva
Skin
• Epidermis, dermis, hypodermis
• Cell type of epidermis: keratinocytes
o Filled with protein keratin
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