Immunology Flashcards
What are pathogens?
Bacteria, viruses or other organisms that cause disease
What does the immune system do?
Defends the human body from pathogens, toxins and cancer cells
What is immunity?
The ability of the body to resist infection by a pathogen or destroy the organism if it succeeds in invading and infecting the body
What is the surface of the skin composed of and what does it do?
Layers of closely packed epithelial cells which form a physical barrier against pathogens
Where are closely-packed epithelial cells found?
In the ski and inner linings of the digestive system and respiratory system
Name chemical secretions that are produced against invading pathogens
- Sweat glands and sebaceous glands in the skin keep the skin at a pH that is too low for most microbes to survive
- Tears and saliva contain the enzyme Lysozyme which digests the cell walls of bacteria and destroys them
- Mucous membrane secrete sticky music which traps microbes
- Epithelial lining of the stomach secretes acid which destroys microbes
What happens when the body suffers a physical injury such as a cut and/or invasion by microbes?
It responds by a localised defence mechanism called an inflammable response at the affected site
What happens after injury?
Mast cells are activated and release large quantities of histamine resulting in blood vessels in the injured area undergoing vasodilation. And capillaries becoming more permeable
What beneficial effects are brought about by the cease of blood flow and permeability of capillary walls during the inflammatory response?
-an accumulation of phagocytes to the damaged tissue as they are attracted by cytokines. (Phagocytes engulf pharaohs by phagocytosis)
-rapid delivery of blood-clotting chemicals (clotting elements) to the injured area (coagulation of blood stops the loss of blood, prevents further infection and marks the start of the tissue repair process)
What do phagocytes do?
Recognise pathogens and destroy them by phagocytosis
Describe the stages of Phagocytosis
1)Phagocytes detects surface antigen molecules present on a pathogen, and move towards it
2)Phagocytes engulf the invader by infolding of the cell membrane to create a vacuole
3)Lysosomes present in the phagocyte’s cytoplasm fuse with the vacuole and release enzymes to digest the invading pathogen
4)The breakdown products are absorbed by the phagocyte
5)Once the invader is digested the Phagocyte releases cytokines which attract more phagocytes to the infected area to continue the battle against pathogens
6)Dead bacteria and phagocytes accumulate at the infected site as pus
What do phagocytes do after contact with a pathogen?
Release cytokines which circulate in the bloodstream and stimulates the specific immune response by activating lymphocytes
What are cytokines?
Protein molecules that act as a signal to other white blood cells causing them to gather at the site of infection
What are lymphocytes?
The white blood cells involved in carrying out the specific immune response
What are lymphocytes made from?
Stem cells in the bone marrow
What do lymphocytes have (membrane receptor)
Single types of membrane receptor which is specific for one antigen
What are antigens?
Molecules, usually proteins located on the surface of cells
What do lymphocytes respond to antigens on?
Invading pathogens
What does antigen binding lead to?
Repeated lymphocyte division resulting in the formation of a clonal population of identical lymphocytes
What are the two types of lymphocytes?
B lymphocytes
T lymphocytes
What do B lymphocytes do?
Produce antibodies against antigens
Describe the structure of an antibody?
Y shaped protein that have receptor binding sites specific to a particular antigen on a pathogen
What do antibodies do?
Bind to antigens, inactivating the pathogen
What can the antigen-antibody complex then be destroyed by?
Phagocytosis leading to the destruction of the pathogens
