2r- Defence against parasitic attack Flashcards
Immune response in mammals has both non-specific and specific aspects. What are examples of non-specific defences?
- physical barriers
- chemical secretions
- inflammatory response
- phagocytes
- natural killer cells which destroy cells infected with viruses
What does epithelial tissue do?
Blocks the entry of parasites
What are examples of chemical secretions that defend against parasites?
- hydrolytic enzymes in mucus
- saliva and tears destroy bacterial cell walls
- low pH environments of the secretions in the stomach
- vagina and sweat glands denature cellular proteins of pathogens
What is inflammatory response?
Injured cells release signalling molecules which results in increased blood flow to the site, bringing antimicrobial proteins and phagocytes
What do phagocytes do?
They engulf the parasite and store them in a vacuole, they then kill the parasite by using powerful enzymes contained in lysosomes
What do natural killer cells do?
They identify and attach to cells infected with viruses, releasing chemicals which lead to cell death by inducing apoptosis
What is an example of a specific cellular defence?
A range of white blood cells constantly circulate the body, monitoring the tissues. If tissues become damaged, cells release cytokines that increase blood flow resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage
What are lymphocytes?
A type of white blood cell which each possess a receptor on its surface, which can potentially recognise a parasite antigen
What does binding of an antigen to a lymphocytes receptor do?
Selects that lymphocyte to then divide and produce a clonal population of the lymphocyte
What will some selected lymphocytes produce?
Antibodies, whilst others can induce apoptosis in parasite-infected cells
What is special about antibodies?
They possess regions where the amino acid sequence varies greatly between different antibodies, this variable region gives the antibody its specificity for binding antigens
What happens when a antigen and a antibody bind?
The antigen-antibody which is formed can result in inactivation of the parasite, rendering it susceptible to a phagocyte, or can stimulate a response that results in cell lysis
What are memory lymphocytes?
Initial antigen exposure produces memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future. When this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration
