Immune System

• Spleen
• Thymus
• Lymph Nodes
• Lymphatic Tissue
• Bone Marrow

• the immune system you are born with
• contains: external barriers, skin, mucous membrane, and secretions which have lysosomes

digest cell wall bacteria

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

• 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

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

White Blood Cells: Phagocytes (neutrophils and macrophages) and Lymphocytes

a foreign particle entering the body

• produced throughout life by the bone marrow
• scavengers remove dead cells and microorganisms

• neutrophils
• macrophages
• monocytes
• eosinophils
• mast cells
• dendritic cells
• basophils

• 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

rapid responses to a broad range of microbes

• skin
• mucous membranes
• secretions

• phagocyte cells
• antimicrobial protiens
• inflammatory response
• natural killer cells

slower responses to specific microbes

• 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

b cells released to make antibodies

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

• 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

An MHC molecule that is on all nucleated cells

An MHC molecule that is on a few cells including dendritic cells, macrophages, and b cells. MHC II cells are antigen presenting cells

• 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

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

• 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

by macrophages

• 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

• o <- antigen
• Y <- antibody
• O <-------------------O <-Activated cd4 (t helper) cell- gives cytokines to stimulate b cell
• | Cytokines
• v
• O <-------- O----------> O
• | |
• v v
• O O
• memory b cell Y Y Y
• Plasma cell

• 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
• ......|...| .......]

• Light Chain
• Heavy chain

immunoglobulins

protiens with sugar

polypeptides

by two disulphide bridges

• 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

• 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

• the clumping together of bacteria, making them less likely to spread
• see drawing

• has 2 antigen binding sites
• sites of action are blood and tissue fluid. they can also cross over the placenta

• they increase macrophage activity (which is an example of an antibody being a label and telling phagocytes to kill)
• antitoxins
• agglutination

• has 10 antigen binding sites
• sites of action are blood and tissue fluid

Agglutination

• has 2 or 4 antigen binding sites
• sites of action are secretions- saliva, tears, small intestine, vaginal, prostate, nasal, and breast milk

• stop bacteria adhering (or attatching) to host cells
• prevents bacteria from forming colonies on mucous membranes

• has 2 antigen binding sites
• sites of action are tissues

• Activate Mast cell
• --> Histamine
• Worm Response

ask

phagocytosis must happen inside the cell first

a protien that activates other immune cells

• 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

• secrete cytokines
• help b cells divide
• stimulate macrophages

kill body cells displaying antigens (MHC1)

remain in body in case the antigen reappears

:)

actual body cells, not b and t cells

:)

• long lasting immunity as a result of exposure to the pathogen or vaccination
• lymphocytes are activated by antigens on the surface of pathogens

• Natural Active Immunity
• Artificial Active Immunity

• aquired due to infection
• --> you build an immunity because you actually got the sickness

• vaccination
• *it takes time for enough b and t cells to be produced to mount an effective response

• 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

• 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

• 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

a preparation containing antigenic material

• whole live microorganisms
• dead microorganisms
• attenuated (harmless) microorganism
• toxoid (harmless form of toxin)
• preparation of harmless antigens

• injected into vein or muscle
• orally

• 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

• caused by the mutation of the virus- change in DNA
• 2 types

• 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

• 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

• 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

• red spots containing transparent fluid all over body
• spots filled with puss
• Eyelids swell and become glued together

• 12%-30% die
• survivors often left blind and disfigured with scabs

• 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

• 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

• last case reported in 1977
• World declared free of smallpox in 1980

• 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

• 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