Flashcards in Unit 4 Deck (30):
What is immunity
the ability of the body to resist infection by a pathogen
or to destroy the organism if it succeeds in invading and infecting the body
What are the two types of immunity?
what is a pathogen?
a micro organism that causes disease (fungi, bacteria, virus)
what is an antigen?
proteins on the surface of cells.
used as a marker to identify a particular cell type
The First Line of Defence
epithelial cell, which form your skin, provide the first line of defence against pathogens provided they remain in tact. the form a physical barrier.
Chemical Defence (1)
secretions from the sebacous glands and sweat glands in the skin. keep the pH level that is too low for most pathogens
Chemical Defence (2)
tears and saliva contain the enzyme lysozyme which digest the cell wall of bacterial cells
Chemical Defence (3)
cells in the mucous membrane secrete sticky mucus that traps microorganisms
Chemical Defence (4)
the epithelial cells in the stomach release acid which destroys microorganisms that have been swallowed
Secondary line of defence - inflammatory response
when the body suffers physical injury it will respond with a localised defence called an inflammatory response
what are phagocytes?
white blood cells that engulf and digest bacteria in a process called phagocytosis
What do MAST Cells do?
release histamine causing vasodilation in blood vessels
what do cytokines do?
signalling molecules which stimulate recruitment of other cell types
engulf pathogens and clean up the injured site
Anti microbial proteins
amplify the immune response
coagulation of blood helps to prevent further infection and starts tissue repair
Stages of inflammatory response
-mast cells activated and release histamine
-histamine stimulates vasodilation of the blood vessels in injured site
-blood vessels become more permeable leak fluid into neighbouring tissues causing swelling
-migration of phagocytes to injured area/migration of antimicrobial proteins to injured area/delivery of blood clotting factors
Natural Killer Cells
stimulate infected cells to commit suicide. apoptosis. infected cells are stimulated to produce a self destructive enzyme.
release cytokines that stimulate a specific immune response
targets one particular pathogen.
involves T & B Lymphocytes
range of white blood cells move around body & constantly monitor the state of tissue.
if damage or invasion of microbes detected, white blood cells detect and release cytokines
any foreign molecule that is recognised by the immune system and produces a response from a lymphocyte.
each lymphocyte has several copies of a single type of antigen receptor on the surface of the membrane.
lymphocyte specific to one antigen.
Clonal Selection Theory
once lymphocyte detected.
dividing repeatedly to form a clonal population of identical lymphocytes
Lymphocytes respond specifically to
Antigens on foreign cells
cells infected by pathogens
toxins released by pathogens
autoimmune disease are a result of failure in regulation of the immune system leads to a T-Lymphocyte immune response to self cells
B Lymphocytes becoming hypersensitive to a normally harmless antigen
triggers an immune response which sensitises to the allergen.
Helper T cells
secrete cytokines that activate phagocytes, cytotoxic t cells and B lymphocytes.
specific HTC then binds to the antigen on the antigen presenting cell.
HTC becomes activated & divides to produce a clone of activated helper cells.
Cytotoxic T Cells
detect & destroy infected cells by several methods including apoptosis.
Antigen Presenting Cells
after a phagocyte destroys an invading pathogen it presents fragments of its antigens on its cell surface.
phagocyte now referred to as an antigen presenting cell