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Name the organs of the immune system.
- Lymph Nodes
- Lymphatic Tissue
- Bone Marrow
What is the innate immune system?
- the immune system you are born with
- contains: external barriers, skin, mucous membrane, and secretions which have lysosomes
What do Lysosomes do?
digest cell wall bacteria
What is your aquired immune system?*
The immune system you aquire over time by memory b cells holding info of antigens so you don't get the same stran of sickness again
What are the types of blood cells?
- red blood cells: also called erythrocytes- anucleate (without a nucleus) biconcave disks that transport O2 to hemoglobin molecules and carry a small amount of CO2 live 100-120 days
- Platelets: cell fragments from megakaryocytes (a cell with many nucleuses). the cell breaks up and each platelet gets a nucleus. help in blood clotting
How are erythrocytes and platelets formed?
bone marrow produces pluripotent (having one or more possible outcome) hematopoietic (formation of blood cells) cells which produce myeloid progenitor cells which end up becomming erythrocytes and platelets
What are the cells of the immune system?
White Blood Cells: Phagocytes (neutrophils and macrophages) and Lymphocytes
What is an Antigen?
a foreign particle entering the body
What are Phagocytes?
- produced throughout life by the bone marrow
- scavengers remove dead cells and microorganisms
What are the phagocytes and their relatives?
- mast cells
- dendritic cells
- 60% of white blood cells
- patrol tissues as they squeeze out of the capillaries
- large mumbers are released during infections
- short lived- die after digesting bacteria
- dead neutrophils make up a large portion of puss
What is innate immunity?
rapid responses to a broad range of microbes
What are the external defenses of innate immune system?
- mucous membranes
What are the internal defenses of the innate immune system?
- phagocyte cells
- antimicrobial protiens
- inflammatory response
- natural killer cells
What is aquired immunity?
slower responses to specific microbes
What are the two responses of Aquired Immunity?
- Humoral (antibody mediated) Response: b cells produce antibodies
- Cell Mediated Response (cytotoxic lymphocytes): cytotoxic means cell killing. these are the t cells
- both b cells and t cells are lymphocytes
see chart of humoral and cell mediated response
b cells released to make antibodies
Cell Mediated Response....
t cells released to kill entire cell
- Larger than neutrophils
- Found in organs not blood
- made in bone marrow as monocytes and are called macrophages once they reach the organs
- long lived
- initiate immune responses as the display antigens from the pathogens to the lymphocytes
What is Antigen Presentation?
- The antigen is broken down in a cell and MHC attatches to a fragment and brings it to the plasma membrane
- in other words after the cell digests the antigen, MHC will take a fragment of the digested antigen and bring it to the cell plasma membrane which presents the antigen to the rest of the body
What is class one MHC?
An MHC molecule that is on all nucleated cells
What is class two MHC
An MHC molecule that is on a few cells including dendritic cells, macrophages, and b cells. MHC II cells are antigen presenting cells
What are the seven steps of phagocytosis?
- 1. Chemotoxis and Adherence of microbe to phagocyte
- 2. Ingestion of microbe by phagocyte
- 3. Formation of phagocyte
- 4. Fusion of a phagocyte with a lysosome to form a phagolysosome
- 5. Digestion of ingested microbe by enzymes
- 6. Formation of residual body containing indigestable material
- 7. Discharge of waste materials
What is a pathogen?
A disease causing node. while an antigen may only be an inflamation causing bacteria that may not cause a disease, a pathogen WILL cause a disease
- produce antibodies- B CELLS ONLY
- b cells mature in the bone marrow then concentrate in lymph nodes (in throat) and spleen
- t cells mature in thymus
- b and t cells mature then circulate in the blood and lymph
- circulation ensures they come into contact with pathogens and eachother
- if lymph nodes are enlarged, when the doctor feels your throat it means you have an infection and are making a lot of b cells
Explain B Lymphocytes
- there are 10 million different types of B lyphocytes, each of which make a different antibody
- the huge variety is caused by the genes coding for antibodies changing slightly during development
- there are a small group of clones for each type of B lymphocytes waiting for if you encounter the disease again
- at the clone stage, antibodies do not leave the b cells
- the antibodies are embedded in the plasma membrane and are called antibody receptors
- when the receptors in the membrane recognize an antigen on the surface of the pathogen, the b cells divide rapidly
How are antigens presented to B cells?
What do B cells divide into?
- memory b cells: which can live for 20 years and will hang around and remember the antigen in case it returns in which it will divide
- plasma cells: secretes antibodies to fight the disease
Diagram for b cells
- o <- antigen
- Y <- antibody
- O <-------------------O <-Activated cd4 (t helper) cell- gives cytokines to stimulate b cell
- | Cytokines
- O <-------- O----------> O
- | |
- v v
- O O
- memory b cell Y Y Y
- Plasma cell
B lymphocytes activate
- plasma cells
- memory b cells
- some activated B cells are plasma cells. these produce lots of antibodies (1000 per second)
- the antibodies travel to the blood, lymph, and lining of gut and lungs
- the number of plasma cells go down a few weeks after the antigen enters because it is pointless to continue to make antibodies, the memory cells stick around instead
- antibodies stay in blood longer, but eventually their numbers go down too
- some activated b cells are memory cells
- memory cells divide rapidly as soon as the antigen is reintroduced
- there are many more clone cells than there were memory cells (ASK)
- when the pathogen/infection infects again it is destroyed before any symptoms show
- .\.\......././...] antigen binding region
- ....\.\././ ......|...| .......]
- ......|...| .......] constant region
What are antibodies also called?
What are globular glycoprotiens?
protiens with sugar
The heavy and light chains of an antibody are..?
How are the light and heavy chains held together?
by two disulphide bridges
Explain the binding sites of antibodies
- each antibody has 2 identical antigen bonding sites- variable regions
- the order of amino acids in the variable region determines the shape of the binding sites
How do antibodies work?
- some act as labels to identify antigens for phagocytes
- -> they tell neutrophils or other phagocytes to kill
- some work as antitoxins
- -> ex: they block toxins such as those causing diptheria and tetanus
- some attach to bacterial flagella making them less active and easier for phagocytes to engulf
- some cause agglutination
What is agglutination?
- the clumping together of bacteria, making them less likely to spread
- see drawing
Explain an IgG antibody
- has 2 antigen binding sites
- sites of action are blood and tissue fluid. they can also cross over the placenta
What is the function of an IgG antigens
- they increase macrophage activity (which is an example of an antibody being a label and telling phagocytes to kill)
Explain an IgM antigen
- has 10 antigen binding sites
- sites of action are blood and tissue fluid
What is the function of an IgM antibody?
Explain and IgA antibody
- has 2 or 4 antigen binding sites
- sites of action are secretions- saliva, tears, small intestine, vaginal, prostate, nasal, and breast milk
What are the functions of IgA antibodies?
- stop bacteria adhering (or attatching) to host cells
- prevents bacteria from forming colonies on mucous membranes
Explain an IgE antibody
- has 2 antigen binding sites
- sites of action are tissues
What are the functions of IgE antibodies?
- Activate Mast cell
- --> Histamine
- Worm Response
In order for antigen presentation to happen....
phagocytosis must happen inside the cell first
What is Cytokine?
a protien that activates other immune cells
Explain T Lymphocytes
- Mature T cells have T receptors which have a very similar structure to antibodies and are specific to one antigen
- they are activated when the receptor comes into contact with the antigen on another host cell
- -->ex: on a macrophage membrane or an invaded body cell
- after activation, the cell divides to form Helper T cells, Cytotoxic T cells, and Memory t cells
T Helper Cells
- secrete cytokines
- help b cells divide
- stimulate macrophages
Cytotoxic T cells
kill body cells displaying antigens (MHC1)
Memory T cells
remain in body in case the antigen reappears
Memorize picture with immunocompetent (activated) cytotoxic t cell
Cytokines are released by...
actual body cells, not b and t cells
Know resting and activated cytotoxic and helper t cells diagram
What is Active Immunity?
- long lasting immunity as a result of exposure to the pathogen or vaccination
- lymphocytes are activated by antigens on the surface of pathogens
What are the two types of Active Immunity?
- Natural Active Immunity
- Artificial Active Immunity
What is Natural Active Immunity?
- aquired due to infection
- --> you build an immunity because you actually got the sickness
What is Artificial Active Immunity?
- *it takes time for enough b and t cells to be produced to mount an effective response
What is Passive Immunity?
- short term immunity as a result of direct injection of antibodies or from passing antibodies from a mother to a child
- b and t cells are not activated and plasma cells have not produced antibodies
- the antigen does not have to be encountered for the body to make antibodies
- antibodies appear immediately in the blood but protection is only temporary
What is Artificial Passive Immunity?
- usded when a very rapid immune response is needed
- -->ex: after infection with tetanus- you need antibodies from someone who has recently had the shot injected into you if you get this
- human antibodies are injected. in the cause of tetanus these are antitoxin antibodies
- antibodies come from blood doners who have recently had tetanus vaccination
- antibody injection only provides SHORT TERM protection as antibodies are destroyed by phagocytes by spleen and liver because the body gets ride of them because they are not your own antibodies, making them foriegn to the body
What is Natural Passive Immunity?
- a mother's antibodies pass across the placenta to the featus and remain for several months
- colostrum (the first breast milk) contains lots of IgA which remains on the surface of the babys gut wall and passes into the blood
What is a vaccination?
a preparation containing antigenic material
A vaccination can be....
- whole live microorganisms
- dead microorganisms
- attenuated (harmless) microorganism
- toxoid (harmless form of toxin)
- preparation of harmless antigens
How can you get a vaccination
- injected into vein or muscle
Why aren't vaccinations always effective?
- Natural infections persist within the body for a long time so the immune system has time to develop an effective response, vaccinations from dead mircoorganisms do not persist for long so you may not have time to build up an immunity
- less effective vaccines need booster injections to stimulate secondary responses (t and b lymphocytes)
- some people dont respond well at all to vaccines bc they may have a defective immune system or may be malnuoutritioned (usually protien common in 3rd world countries)
- no vaccines against protoctists (malaria [mosquitos] and sleeping sickness)
- antigenic variation
- antigenic concealment
What are Antigenic Variations?
- caused by the mutation of the virus- change in DNA
- 2 types
Explain the 2 Types of Antigenic Variation
- Antigenic Drift: small changes, still recognized by memory cells and most likely vaccine will be effective
- Antigenic Shift: large changes, no longer recognized by the immune system and not affected by the vaccine
Explain the no vaccines against protoctists (malaria [mosquitoes] and sleeping sickness [teetsie fly])
- many stages to plamodium (the bacteria that causes malaria). life cycle with many different antigens so vaccinations would have to be effective against all stages or be effective just against infective stage but given in a very small time period- this is not possible
- there is no vaccination for sleeping sickness because Trypanasoma ( the bacteria that causes sleeping sickness) has a thousand different antigens and changes them every 4-5 days
What is Antigenic Concealment
- parasites live inside body cells and hide so immune system doesnt attack
- parasitic worms can hide themselves by covering themselves in host protiens
- HIV is an example of Antigenic Concealment- can live in helper t cells and you may not show symptoms for years
What are the symptoms of small pox?
- red spots containing transparent fluid all over body
- spots filled with puss
- Eyelids swell and become glued together
What is the Mortality of small pox?
- 12%-30% die
- survivors often left blind and disfigured with scabs
What is the Eradication Program?
- program of getting rid of the sickness
- started by the World Health Organization in 1956
- aimed to rid the world of small pox by 1977
What actions did the eradication process take?
- vaccinations and survailence of people
- over 80% of populations at risk were vaccinated
- after any reported case, everyone in the household and 30 surrounding households were vaccinated- called a ring vaccination
What happened to small pox in the end?
- last case reported in 1977
- World declared free of smallpox in 1980
Why was the Eradication Program Successful?
- variola virus stable: the vaccine was cheap and everyone used the same vaccine
- vaccine made from harmless strain of similar virus called vaccinia
- vaccine could be used at high temperatures
- it was easy to identify infected people
- small pox doesnt live dormant and hide like HIV does
What reasons wouldnt the Eradication Process work in some situations?
- poor instability*
- if there is poor infrastructure: people live miles and miles away from town and theres no organized government, so the medicine doesnt get to these people
- unstable microorganisms