6.3 - The body's response to infection Flashcards
(29 cards)
What is meant by non-specific responses to infection?
where the immune system destroys any invading pathogen that enters the body
What is meant by specific immunity?
the immune system targets specific pathogens
What are the 4 main entry routes by which pathogens can enter the body?
- broken skin - direct access to the tissues & bloodstream
- digestive system - contamintated food & drink
- respiratory system - every time we inhale
- mucosal surfaces - lining of body cavities eg. inside of nose, mouth, genitals
what is meant by gram-positive bacteria?
bacteria which have lots of peptidoglycan in their cell walls
What are the 4 physical barriers to pathogens?
- skin
- skin flora
- mucous membrane
- lysozyme
What type of immunity are the physical barriers to pathogens an example of?
non-specific
How does lysozyme respond to infection?
destroys bacterial cells by hydrolysing cell walls of gram-positive bacteria, by digesting the peptidoglycan
What happens to cause inflammation?
damaged white blood cells & mast cells around the injured area releases histamine
histamine makes arterioles dilate to bring more blood to the area - causes redness
histamine makes capillary walls more permeable so plasma fluid, white blood cells & antibodies lead out into affected tissue to cause swelling (oedema)
What cause the skin to be hot when it becomes inflammed?
an increase in metabolic rate in the area - the blood in the area also carries heat energy
What are the two types of phagocytes?
- macrophages
- neutrophils
What happens during phagocytosis?
- bacterium with antigens on their surface are engulfed by phagocyte
- bacterium is enclosed in a phagocytic vacuole
- lysosomes fuse with vacuole & contents are digested by digestive enzymes from the lysosomes
In phagocytosis, what is a lysosome?
a molecule that carries the digestive enzymes
Which non-specific defence is aimed at viruses, aswell as bacteria?
interferon
What are interferons?
proteins produced by virus-infected body cells in response to a virus
What is the response produced by an interferon?
diffuses to surrounding cells & triggers production of a second protein that inhibits viral replication by binding to viral mRNA
- this inhibits viral protein synthesis
What organ system prevents bacteria from being transported around the body in the blood?
lymph system
What is an antigen?
molecules that stimulate an immune response
What are the 2 main types of lymphocytes?
- B lymphocytes (B cells)
- T lymphocytes (T cells)
Why is the lymphocyte response to antigens ‘specific’?
each lymphocytes is specialised to respond to one antigen
Where are T cells made?
bone marrow
Where do the T cells mature?
Thymus
What are the 2 types of T cells?
- T helper cells
- T killer cells
What is the role of T helper cells?
secrete chemicals called cytokines which stimulate other cells to carry out their job
What is the role of T killer cells?
destroy APCs
