2.5d Defence against parasitic attack Flashcards
Immune response
Immune response in mammals has both non-specific and specific aspects.
Non-specific defences definition
Immune system defence mechanisms in organisms that attempt to prevent any parasites from infecting the potential host.
What are the non-specific defenses? - physical barriers
Epithelial tissue blocks the entry of parasites.
What are the non-specific defenses? - inflammatory response
Injured cells release signaling molecules. This results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes.
What are the non-specific defenses? - phagocytes
Killing of parasites’ using powerful enzymes contained in lysosomes by engulfing them and storing them inside a vacuole in the process of phagocytosis.
What are the non-specific defenses? - Natural killer cells
Natural killer cells destroying cells infected with viruses. These cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.
Specific cellular defence
A range of white blood cells constantly circulate, monitoring the tissues. If tissues become damaged or invaded, 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’s special about mammals lymphocytes?
Mammals contain many different lymphocytes, each possessing a receptor on its surface, which can potentially recognise a parasite antigen.
Binding of an antigen to a lymphocyte
Binding of an antigen to a lymphocyte’s receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte.
Some selected lymphocytes will reproduce antibodies, other can induce apoptosis in parasite-infected cells.
What’s different between antibodies?
Antibodies possess regions where the amino acid sequence varies greatly between different antibodies.
This variable region gives the antibody its specificity for binding to antigens.
What’s happens when an antigen binds to antigen-antibody complex?
When the antigen binds to this binding site the antigen-antibody complex formed can result in inactivation of the parasite, rendering it susceptible to a phagocyte, or can stimulate a response that results in cell lysis.
Forming of memory lymphocyte
During initial antigen exposure, memory lymphocyte cells can be produced which are specific for an antigen.
If the same antigen enters the body in the future, a secondary response can be produced by the memory lymphocyte cells.
When this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration.
What are the non-specific defenses? - chemical secretion
hydrolytic enzymes in mucus, saliva, and tears destroy bacterial cell walls;
low pH environments of the secretions of stomach, vagina, and sweat glands denatures cellular proteins of pathogens.
What are T lymphocytes
They are lymphocytes that destroy specific infected or damaged cells by bringing about apoptosis.
What are B Lymphocytes
Cell type which produces antibodies.
