Immunity Flashcards
immune response
a complex series of responses of the body to the entry of a foreign antigen e.g. bacteria, virus, parasite, allergen, tumour cell. Involves the activity of lymphocytes and phagocytes
Non-self
any substance or cell that is recognised by the immune system as being foreign and will stimulate an immune response
Self
substances produced by the body that the immune system does not recognise as foreign, so they do not stimulate and immune response
physical defences to prevent entry/spread of pathogens
• epithelia covering airways
• skin - blocks pathogens from entering the body
• mucous membranes - sticky substance that traps pathogens and contains anti microbial enzymes (chemical) e.g. in mouth, nostrils, ears, genitals, anus
• blood clotting - stops loss of blood and entry of pathogens through wounds (scab)
Chemical defences to prevent entry/spread of pathogens
• skin
• mucous membrane - sticky substance that traps pathogens and contains antimicrobial enzymes
• hydrochloride acid - kills bacteria that we ingest
• blood clotting - stops loss of blood and prevents entry of pathogens though wounds (scab)
Cellular defences to prevent entry/spread of pathogens
• white blood cells - recognise foreign pathogens - have distinctive proteins, glycoproteins, lipids, polysaccharides on their surface
- waste material can also be recognised by WBC
Antigen
Any molecule (usually proteins or polysaccharides) found on surface of cells, which the body recognises as foreign/non-self.
- activates the immune response
Immune response
The actions of lymphocytes in response to the entry of an indigenous in the body
Two types of WBCs
• phagocytes
• lymphocytes
Types of phagocytes
• macrophages
• neutrophils
Phagocytes
• made and stored in bone marrow
• then distributed throughout the body
• remove dead cells and microorganisms
• lobed nucleus
Neutrophils
• form 60% of WBC’s
• released in large numbers during an infection
• short-lived cells - a few days
• engulf bacteria either in blood or in tissue fluids outside the capillaries
• lobed nucleus
Macrophages
• larger than neutrophils
• found in lungs, spleen, kidney, lymph nodes
• made and stored in bone marrow
• travel in blood as monocytes
• monocytes develop in =to macrophages once they leave the blood and settle in the organs, removing any foreign material
• long-lived cells - several months
• initiate immune response
• don’t completely destroy pathogens - cut them up and display antigens (APC) that can be recognised by lymphocytes
• kidney bean shaped nucleus
Phagocytosis
• pathogens invade the body, causing infection and attacking cells
• cells being attacked release histamine (chemical)
• histamine and pathogenic chemicals attract neutrophils and macrophages to the site of infection - attraction is called chemotaxis
• bacterium attaches to macrophage membrane. If bacteria is covered by antibodies, neutrophils have specific receptions to the antibody which recognised and attaches to them
• endocytosis - plasma membrane of macrophage engulfs the pathogen and traps it within the vacuole
• lysosomes (contain lysozyme enzymes) fuse with the phagocytic vacuole
• lysozymes are released into the vacuole, killing the bacteria
• protease enzyme may also be present in digesting the bacteria (by breaking down proteins)
• antigens of bacteria are embedded in the CSM of macrophage alerting and activating B and T cells to the area
• macrophages with antigens on their surfaces are known as antigen-presenting cells
Neutrophils have a short life so may…
What does this result in
Die straight after killing and digesting pathogens
Results in neutrophils collecting at site of infecting and forming pus
Size of lymphocytes
Small compared to phagocytes
Large lumen in comparison to their size
Large nucleus that makes up most of cell
Where are lymphocytes made
Bone marrow
Each lymphocyte contains…
a set of genes that codes for a particular type of receptor
Types of lymphocytes
B and T-lymphocytes
Where are B-lymphocytes made and matured
Made in bone marrow, mature in bone marrow
B-lymphocytes process
• made in bone marrow and stored there until it matures
• after maturing, they spread through the body, mainly to the lymph nodes and spleen
• each B cell has the ability to make one specific type of antibody molecule
• once the B cell has been activated by the antigen, it will divide by mitosis and produces a clone of genetically identical cells - B plasma and B memory cells
• B plasma cells produce one specific type of antibody
• at this stage, the antibody has not been released by the B cell yet so remains within the plasma membrane
• antibody forms a protein receptor - has ability to combine specifically with one type of complimentary antigen, forming an antigen-antibody complex
• antibody receptors are then found in the plasma membrane of the B-lymphocyte - can now bind specifically to one type of complimentary antigen molecule
• B-lymphocyte produce antibodies from plasma cells
• plasma cells are short-lived
• B memory cells live in the body for a much longer time (years), maybe even a lifetime
• the more the person is exposed to the same antigen, each time, even more B memory cells are made and remain, thus becoming increasingly more efficient at removing the pathogen
What happens when bacteria with its antigens invade the body?
• phagocytosis
• antigens on macrophage surface/bacteria, are recognised by certain specific B-lymphocytes - has a specific antibody receptor that is specific to he shape of the antigen
• specific B-cells are activated
• activated cells divide by mitosis and form a clone of genetically identical B-cells
• differentiate into B-plasma cells or B-memory cells
- B-plasma cells produce the specific antibodies that specifically combine with the antigen that has entered the body destroying it
• T-helper cells release cytokines - stimulate B cells to form a clone of identical e cells by mitosis
• when the same bacteria with its antigen invades the body for a second time, the B-memory cells divide rapidly and develop into B-plasma cells (and more memory cells)
• same processes occur (production of B plasma cells…) again at a much faster rate
- B plasma cells are made very quickly so specific antibodies are made very quickly
• now the infection can be destroyed and removed before any symptoms of the disease develop
Phagocytosis simple definition
Patronages engulf the pathogens bearing the antigens on their cell surface membrane
Summary of B-lymphocyte process
activated B cells —> divide by mitosis to produce a clone —> differentiate into B plasma and B memory cells
