10 disease and immunity Flashcards
Pathogens
Microorganisms that cause disease.
Host
An organism that contains foreign DNA or a pathogen.
Bacteria
Small, single-celled organism with no nucleus (plural: bacterium).
Fungi
A group of organisms that includes moulds, yeasts and mushrooms.
Protocists
Protoctists are mostly unicellular (and sometimes multicellular) organisms that have cells with a nucleus.
Viruses
Microscopic particle consisting of genetic material surrounded by a protein coat.
Transmissible diseases
A disease in which a pathogen can be passed from one host to another.
Some transmissible diseases and their pathogens
Disease Type of pathogen
cholera bacterium
athlete’s foot fungus
malaria protoctist
common cold virus
Pathogens can be transmitted from an infected person to an uninfected person by:
Direct contact through body fluids such as blood
Indirect contact, such as from the air, through water or food, contaminated surfaces or animals.
The first line of defence
The body’s initial defence against disease: non-specific physical or mechnical barriers that prevent pathogens from entering the body.
Immune system
Organ system, tissues and cells involved in protecting the body against infection by pathogens.
Second line of defence
The immune system is the second line of defence if a pathogen passes the first line of defence, enters the body and causes an infection. White blood cells, phagocytes and lymphocytes, detect and destroy pathogens.
Mechanical barriers
Barriers that prevent the entry of pathogens into the body.
Chemical barriers
Barriers in the body that trap and kill pathogens.
White blood cells and how they work
A plasmid containing a foreign gene or sequence of DNA.
Depending upon the type of white blood cell, they can:
Surround and engulf a pathogen (phagocytosis) then destroy it
Produce antibodies, proteins which attach to pathogens and so mark them for destruction.
The spread of disease can be controlled by preventing pathogens being transmitted to uninfected individuals. This involves:
A clean water supply
Good personal hygiene
Hygienic food preparation
Proper waste disposal
Treatment of sewage.
Active immunity
Immunity that develops in response to a pathogen and involves the activation of memory cells.
Antigens
Substances that trigger the immune response and cause the production of antibodies.
Lymphocytes
Type of white blood cells that produce antibodies.
Antibody
Antibodies are proteins produced by lymphocytes (a type of white blood cell).
An antibody for a particular antigen has a shape that fits, or is complementary to, the shape of that antigen.
This means the antibody can attach to an antigen on the surface of the pathogen.
Once it is attached to an antigen, the antibody can:
mark the pathogen for phagocytosis and destruction by phagocytes, or
cause the pathogen to break open and die (direct destruction)
Once it is attached to an antigen, the antibody can:
Mark the pathogen for phagocytosis and destruction by phagocytes, or
Cause the pathogen to break open and die (direct destruction).
Memory cell
A cell that forms from a lymphocyte as the immune system responds to an infection. It remains in the bloodstream and can recognise pathogens that infect after a first infection. It then differentiates to form antibody-producing lymphocytes that mount a secondary response.
How vaccines work
A vaccine contains small amounts of material from the pathogen, or dead or weakened pathogens that cannot cause disease. The vaccine is introduced into the body
Lymphocytes in the immune system mount a primary response to the antigens from the pathogen. They make antibodies to target these antigens, and they also produce memory cells. These memory cells remain in the blood after the pathogen has been destroyed.
If a vaccinated person is infected by the live pathogen, the memory cells will recognise it very quickly. A secondary immune response is mounted, which destroys the pathogen, often before symptoms develop.
Immunisation programmes
Young children may receive vaccinations against a wide range of infections, including measles, mumps, rubella, whooping cough, diphtheria and polio.
Teenage girls may be vaccinated against HPV (human papilloma virus) to protect against cervical cancer.
Passive immunity
Immunity is gained when antibodies are transferred to the body from another individual, such as from a mother to her baby.
Memory cells are not produced in passive immunity.
The protection usually lasts only a few weeks or months, but
Protection happens immediately because the antibodies recognise the pathogen straightaway, which leads to their destruction.
Natural immunity
Natural immunity happens after you get infected by a germ and your immune system responds by making antibodies to it.
Artificial immunity
Artificial immunity is a mean by which the body is given immunity to a disease by intentional exposure to small quantities of it
Cholera
Bacterial infection caused by water or food contaminated with the bacterium Vibrio cholerae.
Toxin
A substance that can cause injury or death when in the body.
Effect of the cholera toxin
Once the bacteria enter the body, they find their way to the small intestine.
(And yes, they survive the passage through the acidic stomach.)
Inside the small intestine, the bacteria start producing the cholera toxin.
The toxin causes the intestinal cells to secrete chloride ions into the lumen of the intestine.
The high concentration of chloride ions causes osmotic movement of large amounts of water into the intestinal lumen.
This in turn leads to watery diarrhoea, severe dehydration and loss of ions from the blood.
