Immunity Flashcards
What are the 2 types of defence mechanism and what are their characteristics?
1) None specific- same response for all pathogens and it is immediate
2) Specific response- different response for all pathogens and it is slow
What are the 4 main barriers to disease?
1) Epidermis of skin
2) Mucus membranes
3) Ciliated epithelia
4) HCl in the stomach
What is phagocytosis?
The process by which pathogens are engulfed and destroyed by leukocytes
Where are red, white and platelets cells formed?
The bone marrow
What are the 2 types of phagocytes?
Neutrophils and Macrophages
What are the 7 steps of phagocytosis?
1) Chemotaxis and adherence of microbe to the phagocyte
2) Ingestion of the microbe
3) Formation of a phagosome (vesicle + microbe)
4) Formation of a phagolysomes (lysosome + phagosome)
5) Digestion of ingested microbe by enzymes
6) The formation of the residual body which cannot be broken down by the enzymes
7) Discharge of material
What are the 2 physical effects of phagocytosis?
1) Inflammation at the site of infection
2) Puss (dead bacteria + phagocytes)
What causes inflammation?
The release of histamine which usually causes dilation of blood vessels
What is the role of a T lymphocyte?
Respond to an organism own cells that have been invaded by foreign material
What are antigen presenting cells?
Cells which present antigens of other cells on their own self surface membrane
Where are T lymphocytes formed and stored?
Formed in the bone marrow and collect in the thymus
What are 2 types of T lymphocytes?
1) T helper cells
2) T killer (cytotoxic) cells
What are the 2 roles of T helper cells?
1) Formation of memory cells by mitosis
2) Cytokine secretion which stimulates phagocytes and B lymphocyte division
What are the 2 roles of cytotoxic cells?
1) Produce a protein called Preforin which makes a hole in the membrane of the infected body cell
2) Secretes toxins to kill the cell
What is the name given to an antibody + antigen?
Antigen-antibody complex
What are the 4 functions of antibodies?
1) Prevent entry of viruses or toxins into the host cell
2) Immobilise bacteria by binding to flagella
3) Agglutinate bacteria
4) Coat bacteria which identifies them for phagocytosis
What are the 3 ethical issues of monoclonal antibody formation?
1) Involves use of animals
2) Involves genetic engineering which some groups of people do not agree with
3) Introduction to the monoclonal antibody presents danger to the human
Where are B lymphocytes produced and matured?
Bone marrow
What is an antigen?
A molecule that produces an immune response
What are the 4 steps in the humoral response?
1) Circulating antibodies will attach to antigens of the surface of the pathogen or toxin
2) T helper cells signals B cells to rapidly divide and form genetically identical daughter cells
3) Some daughter cells develop into plasma cells which produces large amounts of specific antibody
4) Other plasma cells become memory cells
What happens in the primary immune response?
Plasma cells (short life span) secrete antibodies and memory cells (long life span) are produced which circulate in the blood
What happens in the secondary immune response?
A smaller amount of antigen will induce an immune response because memory cells are present.
The response is more rapid and more antibody is produced.
What are the 3 types of vaccination?
1) Live attenuated
2) Dead
3) Genetically engineered
What is the herd immunity effect?
The effect of immunising a sufficiently large number of people to protect an entire population from the spread of a particular disease.
What 3 factors contribute to the effectiveness of herd immunity?
1) Population density
2) Route transmission
3) Biology of the disease
What are the 5 problems with vaccines?
1) Vaccine can cause disease and then can be passed on to others
2) People decline vaccines
3) Vaccines don’t work on everyone
4) Impossible to vaccinate against every disease
5) Pathogen may mutate often
Why is control of cholera by vaccination difficult?
1) Cholera is an intestinal disease thus not easily reached by the immune system
2) Antigens of cholera mutate rapidly
Why is control of TB by vaccination difficult?
1) Elderly population is increasing. They have less effective immune systems so vaccination is less effective
2) Mobile populations from the East due to poverty, wars and political unrest
Why should scientific evidence be treated with caution?
1) Scientific theory should be critically appraised
2) Some scientist have vested interests
3) Media may portray evidence in a bias way
