infection Flashcards
antigen
any molecule the body recognises as ‘foreign’ or ‘non-self’
lysozymes
found in tears, saliva and nasal secretions
kills bacteria by breaking down their cell walls
- hydrolyses the polysaccharide in cell wall
inflammation
helps to destroy invading microbes
damaged wbcs and mast cells release histamine in inflammatory response
hisamine
released by damaged wbcs and mast cells in inflammatory response
increases blood flow in capillaries at infected site
causes arterioles in infected area to dilate
increases permeability of capillaries so vessels leak
- plasma, wbcs and antibodies leak from blood to tissues causing swelling
- allwos infecting microbes to be attacked by intact wbcs
phagocytosis
phogocytes engulf bacteria + foreign matter in blood and tissues
- includes nuetrophils and macrophages
bacteria present-> engulfed by phagocyte -> enclosed in vacuole -> lysosomes containing digestive enzymes fuse with vacuole and release enzymes to destroy bacteria
lymph
tissue fluid drains into lymphatic vessels, flows along lymph vessels and passes lymph nodes
as lymph passes through the lymph nodes, present pathogens activate lymphocytes and macrophages- which destroy microbes
lymph returns to the blood via lymphatic and thoracic ducts
interferon
provides non specific defence against viruses
produced by microbe-infected cells
- diffuses to surrounding cells and prevents microbes from multiplying by inhibiting microbial protein synthesis
lymphocytes
wbc which circulate in blood and lymph
supplies of lymphocytes held in lymphoid tissue
B lymphocytes
produced in bone marrow
each has a specific type of antigen receptor on cell surface
B cell activated when its receptor bins to an antigen with a complementary shape
- secretes antibodies when activated
antibodies
immunoglobulins
bind to antigens on the microbe cell surface membrane
act as labels allowing phagocytes to recognise and destroy the cell
T lymphocytes
produced in bone marrow and mature in THYMUS gland
- mature t cells move to lymph nodes and spleen
specific receptor on surface only binds to antigen with complementary shape
activated by present pathogens as lymph fluid passes through lymph nodes/ present pathogens when blood passes through the spleen
T helper cells
when activated: stimulate B cells to divide so they are capable of producing antibodies)
enhance activity of phagocytes
t killer cells
destroy any cells with antigens on their cell surface membrane
including: any body cells infected with pathogens and transplants
activation of t helper cells
t helper cell with complementary shaped CD4 receptors binds to antigen on APC
this activates THC and causes it to divide to produce a clone of active THC and clone of t memory cell
APC
proteins attached to macrophages as ‘non-self’ antigens
alerts immune system to presence of foreign antigens
benefit of t memory cells
can stay in body for years
allows for quick specific immune response if later infected with same antigen
cloning b cells
receptors on B cells bind to ‘non-self- antigens and become APCs
APBC bind with active, cloned t helper cells presenting same antigen
release cytokines which stimulate division and differentiation of b cells
produce b effector cells or b memory cells
role of cytokines
stimulate division and differentiation of b cells to produce b effector cells or b memory cells
B effector cells
differentiate to produce plasma cells
release antibodies into blood and lymph
only last a few days
b memory cells
can stay in body for years
allow for a faster immune response if infected with same antigen in future
t killer cells explained
bind to complementary antigen presented on body cell
divide to form active clone
- division aided by cytokines produced by t helper cells
produce enzymes that create pores in membrane of infected cell
enable ions and water to flow into cell so it swells and bursts
pathogens within cell released and labelled by b cells as targets for destruction
secondary immune response
b memory cells produced in primary immune response can differentiate immediately to produce plasma cells and release antibodies
invading bacteria is destroyed so quickly there are usually no symptoms
