Unit 4 AOS3 Flashcards
Pathogen
An agent that causes disease.
Antigen
Any molecule that triggers an immune response.
(Interacts with immune system).
Allergen
Non-pathogenic antigen that triggers an allergic reaction.
How does the immune system protect the body?
By scanning and destroying pathogens.
2 antigen types
- Self-antigens.
- Non-self antigens.
Self-antigens
Located on the surface of cells, mark the cell as ‘self’ so the immune system doesn’t attack.
MHC I markers
MHC II markers.
MHC I markers
Expressed on all nucleated cells; Identifies cells as self.
MHC II markers
Found on specialised cells of the immune system,
Allow antigen-presenting cells to show T helper cells foreign antigens which in turn kicks of the adaptive immune response.
MHC
Major Histocompatibility Complex Proteins
MHC proteins differ between individuals.
Non-self antigen
A molecule from outside the body that is recognised by the immune system and initiates an immune response attack.
Malfunctions involving antigens
The immune system results in the recognition of self-antigens as non-self. So immune system attacks self-cells; healthy cells (Autoimmune disease)
Red Blood Cells
Red blood cells have no MHC proteins.
Type A —> A antibodies.
Types of Pathogens
Cellular and Non-cellular pathogens.
Cellular pathogens
cellular structure + living organism
- Bacteria.
- Fungi.
- Worms.
- Protozoa.
Bacteria
- Unicellular prokaryotes.
- Cause disease through toxins and enzymes. Affecting the functioning of cells or causing death.
Fungi
- Eukaryotic
- Yeast, moulds containing filaments called hyphae
Thrush and Ringworm
Worms
- Multicellular invertebrate.
- Egg, larval + adult stages.
- 55m
Protozoa
- Single-cell eukaryotic.
- Free-living or parasitic.
- Inhibit nucleic acid synthesis, protein synthesis and cellular respiration.
eg. Malaria.
Non-cellular pathogens
- Viruses
- Prions.
Viruses
- Composed of genetic material inside a protein coat, sometimes covered in a lipid envelope.
- Not able to independently reproduce, so they insert genetic material into the host’s cell used for cell replication.
Prions
- Abnormally folded proteins with the ability to induce normal proteins to become misfolded.
- Only occurs in mammals and affects the brain and other neural structures.
- Contain no nucleic acids.
First Line of Defence
Physical, chemical and microbiological barriers preventing pathogenic invasion.
Innate immune system
Component of an immune system composed of generalised and non-specific defences and/or response to pathogens.
1st and 2nd line of defence.
Barriers in plants
- Physical.
- Chemical.