immunology option Flashcards
how does a pathogen try and get into the body?
tries to enter through body through hole e.g. eyes, cuts
pathogen enters body tissue and tries to reach blood supply via a capillary
(responses include inflammation and phagocytosis)
pathogen enters blood supply and can migrate around body target cells to reproduce
(response includes B, T and memory cells)
what is the first line of defence?
natural barriers
e.g. eyes, skin, ears
how do eyes protect against pathogens?
produce tears containing antibodies and lysozymes
how do ears protect against pathogens?
produce wax which traps pathogens and contains lysozymes
what does ciliated mucous membranes do in the gut, genitals, anus, ears, nose and respiratory pathways?
sticky mucus lines passage to trap pathogens
how does the respiratory tract protect against pathogens?
ciliated cells which waft mucus to the top of the trachea, mucus is swallowed and passes into stomach acid
what does the epithelial layer of cells do to protect against pathogens?
contains mucus producing goblet cells
how does the skin protect against pathogens?
outer layer of epidermis
consists of dead keratinised cells
act as a physical barrier
what does skin flora do?
commensal bacteria which competes with pathogenic bacteria
how does the mouth protect against pathogens?
lysozyme in saliva
how does the urethra protect against pathogens?
flow of urine
how does the vagina protect against pathogens?
acidic
mucus
how does blood clotting protect against pathogens?
seals wound to prevent pathogen from entering
what is lysozyme?
in tears and saliva
enzyme attacks peptidoglycan in cell walls of gram-positive bacteria
what is the second line of defence?
inflammation
phagocytosis
what does inflammation cause?
redness
swelling
heat
pain
what is the function of inflammation?
increase blood flow to the area
destroy cause of infection replace and repair damaged tissue
limits effects on body by confining infection to small area
what does phagocytosis do?
localises any break in barrier and destroys invading microorganisms
what are phagocytes?
non specific white blood cells
(neutrophils and macrophages)
what do neutrophils and macrophages do?
engulf and digest foreign particle
what happens during phagocytosis?
chemotaxis and adherence of microbe to phagocyte
ingestion of microbe by phagocyte (engulf)
formation of phagosome with lysosome to form phagolysosome
digestion of ingested microbe by enzymes formation of residual body and discharge of waste materials
what do neutrophils do?
engulf and destroy pathogens
numbers rise as a result of infection
short lived
what do macrophages do?
engulf pathogen and then present antigen on surface
long lived
settle in lymph nodes, spleen and kidney
what is the third line of defence?
response to an antigen involving lymphocytes due to antigens being recognised as foreign
what is the humoral response?
B lymphocytes
what is the cell mediated response?
T lymphocytes
what are antigens?
proteins/polysaccharides/glycoproteins
specific shape
on surface of bacteria/virus/foreign tissue
can be free molecules e.g. toxins
what are antibodies?
large protein molecules that can recognise and neutralise antigens
specific shape complementary to that antigen
quaternary structure proteins (2 heavy, 2 light chains)
what are the 3 ways antibodies are able to combat pathogens?
neutralisation
aggulation
opsonisation
what happens during neutralisation?
antigens which are toxic are rendered harmless if blocked by being bound to an antibody
what happens during aggulation?
forming antibody-antigen complexes so pathogens are held together in large clumps
pathogens cannot move and invade cells
macrophages and neutrophils can move more easily to engulf pathogen
what happens during opsonisation?
antibodies coat antigens to help the immune system recognise them
phagocytes have receptors which enable them to bind to and engulf microbes coated with antigen
what are the properties of lymphocytes?
produced by stem cells in bone marrow
have specialised receptors on plasma membranes
what do B lymphocytes do?
originate in bone marrow
mature in spleen and lymph nodes
develop into plasma B cells (and memory)
plasma B cells secrete antibodies
memory B cells remain in body for years and act as an immunological memory
what do T lymphocytes do?
originate in bone marrow
migrate to thymus gland to mature
develop into T helper, killer, memory and suppressor cells
what do T helper cells do?
release cytokines which stimulate B lymphocyte cells to develop and stimulate phagocytosis
what do plasma B cells do?
secrete antibodies
what do T killer cells do?
attack and kill infected cells
what do T suppressor cells do?
turn off immune response when infection is cleared
what happens to cells with self-antigens?
deleted soon after formation otherwise our own body cell would be destroyed
why do you feel ill for a period of time before getting better?
body produces millions of B and T lymphocytes which are all specific to different antigens
time is taken to find the right cell and then for that cell to increase in number
what is the function of clonal selection?
to activate B and T lymphocytes
what happens during clonal selection?
pathogen enters body and produces toxin
phagocytosis and antigen presentation by macrophages
macrophages must find specific B and T cell that is complementary to bind to antigen
antigen binds to complementary receptor of B or T cell so cell is activated
selected cell then divides rapidly by mitosis (clonal expansion)
what is the cell mediated response?
when T cell is clonally selected so differentiates into killer, helper and memory T cells
what is the humoral response?
when a B cell is clonally selected so differentiates into plasma and memory B cells
why is there a delay (lag phase) on graph?
due to clonal selection and expansion
where is there not a delay (lag phase) if infected for a second time?
memory B cells are present
what is natural immuntiy?
gained in normal course of living processes
what is artificial immunity?
gained by deliberate exposure to antigens/antibodies
what is active immunity?
caused by introduction of the antigen
what is passive immunity?
introduction of antibody
what is an example of passive natural immunity?
antibodies are given via placenta or breast milk
what is an example of passive artificial immunity?
antibodies given by injection
what is an example of active natural immuntiy?
antibodies made by persons own immune system from infection