IMMUNITY Flashcards
Define Immunity
immunity is the resistance to infectious disease.
What are the type of cells which provide defence against infection?
WBC, which are also known as leukocytes
Where are WBC created?
derived from stem cells in own barrow
What does the lymphatic system consist of?
lymphatic vessels, and lymph nodes
Where do B cells and c cells originate ?
b- born marrow
t- thymus
What occurs in the lymph nodes?
lymph nodes are the sites where any new foreign antigen meet and activate B cells and T cells. where immune response occurs
What are the two main sub divisions of immune system?
- innate and adaptive
What are the main differenced between the innate immunity and adaptive immunity ?
- specificity of response
- pathogens it responds to
- whether it is developed of innate
- major responses
What are the three divisions of the immune system?
1st line- physical, chemical and flora barriers
2nd line- live actions, cells of immune system, soluble proteins, that mounts a rapid non-specific attack against pathogens
3rd line- actions of immune cells ad antibodies specifically tailored to pathogen.
When is the 3rd line of defence activated?
the adaptive immune system only comes into operation only if the second line of defence fails.
What are the major barriers of the first line of defence ?
- Intact skin
- Mucous membrane and their secretions
- presence of normal flora
How does intact skin act as a defence barrier?
constitutes an important physical and chemical barrier to microbial infections.
the constant shedding of dead surface cells is an effective barrier against pathogens
sebaceous glands in the skin produce sebum= protective antimicrobial film on the skin
How does mucous membrane and their secretions act as a defence barrier?
is the interspace of the airways, gut and urogenital tract are lined with mucous membrane consisting of ethical cells. adjacent cells have tight junctions which prevent entry of microbes
airways recreate mucous which traps entering pathogens, and the cilia moves the mucus up and out
How does flora at as a defence barrier?
flora is a non-pathogenic bacteria that are normal residents in specific areas of the body, inhibits growth of pathogenic microbes
What is the 2nd line of defence?
2nd line of defence involves the actions of immune cells and soluble proteins that produce inflammation
what is inflammation?
localised protective repose to infection
What are the main phagocytic cells in the innate immune system?
neutrophils, macrophages and dendritic cells.
Define phagocytosis
bulk engulfment of solid material into cells
What is the purpose of phagocytes in the immune response?
to ingulf extracellular pathogens in the blood or tissue. This involves the direct attacking of pathogens
What is the purpose of NKC in the innate response?
to eliminate, through apoptosi,s cells that are already infected by pathogen. NKC use a process known as degranulation
Define degranulation
the process used by NKC and cytotoxic T cells to eliminate infected body cells by releasing antimicrobial and toxic granules into abnormal cells
Where are neutrophils and macrophages generally found? in respective order
circulating the blood stream, in tissue close to epithelial layer
What is degranulation?
degranulation is the release of anti-microbial and toxic molecules from membrane bound granules in cytoplasm of immune cells
What do the granules in NK cells contain?
protease enzymes and perofit(pore forming proteins )
Why is it important that infected cells are killed by apoptosis rather than lysis?
if the cell explodes the pathogens are released into the extracellular fluid where it may spread. whereas apoptosis will destroy both the cell and virus
How do NK cells determine whether to kill or not kill a cell?
whether or not the NK will kill a cell is determined by 2 receptors 1.kill receptors 2.inhibitry receptors.
Why are healthy body cells not killed by NK cells?
healthy body cells will have normal MHC m1 markers that bind to complimentary inhibitory receptor of NK cell
What do viruses and cancer do to cell markers so that the NK cell will eliminate the infected cell?
suppress the expression of normal HLA or MHC markers whereas cancer cells produce abnormal markers
What is the purpose of compliment proteins?
they are inactive enzymes circulating in the blood stream, that when activated, complement or add to the function of immune cells
How are compliment proteins activated ?
they are activated when the make direct contact with molecules on the surface of a pathogen
What are interferons?
signalling molecules that recreate messages(paracrine signalling) messages to nearby neighbouring cells to prepare for a possible virus infections
What can interferons cause nearby neighbouring cells to do?
- induce transcription of genes that code for inactive antiviral enzymes
- make plasma membrane less permeable
- activate immune cells ,NK
Define inflammation
inflammation is normally a short term (acute) immune response that is localised around the site of entry of the pathogen
What are the two stages of inflammations ?
- The vascular stage
- dilation of blood vessel
- increased permeability of blood capillaries - the cellular stage of inflammation
- escape of immune cells from capillaries
- migration of neutrophils to immune sites
Describe the vascular stage of inflammations
- 1 dilation of blood vessels
- the trigger for the dilation of blood vessels is the release of chemicals including histamines which cause vasodilation, blood flow and heat - 2 increased permeability
- become more leaky so tat protein rich fluid escapes the capillaries into infected region. this intern causing swelling and clotting
Describe the cellular stage of inflammations
- 1 escape of immune cells from capillaries
- the expansions of the cappillary bed enables neutrophils to squeeze between endothelial cells - 2 migration of neutrophils in infection sites
- the first immune cell to the infected site is the neutrophil, which is attracted by the cytokines of damaged cells
Define adaptive immunity
is also known as acquired immunity because we develop this form of immunity through contact with various pathogen. it only initiates action if the innate immunity has failed to stop the infection
What are the three distinguishing features of adaptive immunity ?
- specifity
- tolerance
- memory
Describe specificity
adpative immunity is specific because its response is tailor made to recognise each antigen involved in the infection. only specific adaptive immune cells that can recognise pathogens are selected and proliferated
Describe tolerance
self tolerant and immune cells will not normally respond to antigens on normal healthy body cells.
Describe memory
the adaptive immune system had the ability to remember previous antigens to which it has respond.
What is the humoral immunity pathway ?
the humeral pathway involves the actions of antibodies that identify and bind to extracellular pathogens and other toxins. antibodies are produced by plasma B cells
What is the cell meditated immunity pathway ?
involves various actions of T cells. cytotoxic T cells eliminate infected body cells that have missing or abnormal MHC 1 markers.eliminate extracellular pathogen s
What do antibodies do ?
directly identify and bind to extracellular foreign antigens, either neutralising them or tagging them for destruction .
In what two ways to antigens defend the body?
- antibodies bind to surface antigens on pathogens forming a coating that neutralises them by blocking their receptors
- binding to surface antigens on antibodies tag pathogens for destructions
What is the basic stricture of antibodies ?
two heavy chains and two light chains
