specific resistance to infection

what is the immune system?

is composed of cells and proteins that protect against foreign organisms, a range of alien chemicals as well as cancerous and other abnormal cells.

what is specific resistance to an infection?

is defenses tailored to each individual pathogen to overcome infection and respond quickly if subsequent encounters to clear inflection before symptoms develop. It creates “memory” to prevent getting it again

what is an example of a specific resistance to a disease?

if you get I infected or vaccinated with the chickenpox virus, your body will make antibodies to combat this virus. these antibodies only being effective against the chickenpox virus and not any other virus/ bacterium

What does the immune system consist of?

some of the cells being non specific such as phagocytes (cells that engulf and digest micro-organism and cell debris then presenting antigen on their surface to lymphocyte) these are antigen presenting cells. And some being specific such as lymphocytes (B and T cells)

what do lymphocytes do?

they receive antigen and trigger specific immunity (cell mediated and antibody mediated)

B and T cells only…

provide protection against a specific micro-organism or disease causing substance

what is it called when B and T cells react?

an immune response

an immune response is…

a homeostatic mechanism, this is because when micro-organisms or foreign substances enter the body, the immune response helps to deal with the invasion and restore the internal environment to normal condition

what cells make up the majority of the lymphoid tissues?

B and T cells

what cells are involved in antibody mediated (humoural immunity)

B - cells

what cells are involved in cell mediated immunity?

T- cells

where lymphocytes produced?

the B and T cells are both produced in the bone marrow and end up in lymphoid tissue. Half of the cells go to the thymus where they mature into T cells before being incooperated into lymphoid tissue and the blood. Whilst the other half go to the bone marrow to become B-cells and then become part of the lymphoid tissue and the blood.

where is there lymphoid tissue?

out of the lymphoid tissue is in the lymph nodes, however it also occurs in other parts of the body such as the spleen, thymus gland and tonsil.

what is the simple way to describe the humeral response or the anti-body mediated immunity?

this involves the production of special proteins called antibodies by B-cells, which circulate around the body and attack invading antigens

what is the simple way to describe the cell mediated response?

this is due to T-cellls and involves the formation of special lymphocytes that destroy the invading agents

is an immune response always due to a pathogen?

not always, allergy occurs when the immune system reacts to a substance that is not harmful

what kind of molecules are antigens?

they are usually large molecules such as proteins carbohydrates, lipids, or nucleic acids

antibody mediated and cell mediated immunity are both triggered. by what?

antigens

what is the definition of an antigen?

is a substance capable of producing ah immune response, is the part of the pathogen that triggers the immune response “antigenic site”

what are some examples of antigens?

• virus particles

• whole micro-organisms, such as a bacterial cell

• part of a bacterium, such as the flagella, cell wall or capsule

• toxins

• molecules off cells such as blood cells

• pollen grains

• egg whites

• part of protein coat

• foreign tissue (e.g donor blood or tissue)

why do large molecules produced in a persons own body not cause an immune response?

as these are self antigens, whereas foreign compounds that do trigger an immune response are non self antigens. Our body is programmed to distinguish between them before birth to only attack non self antigens

what are antigen presenting cells?

these are phagocytes that ingest pathogens as part of the non specific response. They then present the antigen (part of the pathogen that the immune system recognised on their surface) They present the antigen to lymphocytes which are involved in the specific immune response

some antigen presenting cells include;

• macrophages

• some lymphocytes

• dendritic cells

• undifferentiated B cells

when are antibodies produced?

they are produced during antibody mediated immunity in response to non self antigens

what is an antibody?

it is a Y shaped specialised protein that is produced by plasma cells, they have active sites/ receptors that bind to specific antigen that will form an antigen- antibody complex. This occurs are antigen molecules have specific active sited with a particular shape and the antibody has the complementary shape (lock and key model)

how is the lock and key model relevant in antibodies and antigens?

antigen molecules have specific active sites with a particular shape and the antibody has the complementary shape. Allowing molecules to fit together like a key in a lock. Each antibody can combine with only one particular antigen the same way that a key will only open one particular lock

what group are antibodies are part of?

antibodies belonging to a group of proteins known as immunoglobulins

what are the different types of proteins of immunoglobulins are antibodies belonging to?

IgA, IgE, IgD, IgG, IgM

how do antibodies work against antigens?

antibodies surround pathogens and neutralise them in various ways by binding to their antigenic sites

what is the part of an antibody that binds to the antigens?

the antigen binding fragment

specific immunity is effective for pathogens that…

produce consistent antigenic sites

what is a pathogen that has consistent antigenic sites?

the measles, therefore the first time the body is encountered with measles, APC present the antigen to lymphocytes which act specifically to destroy the measles virus. So that memory lymphocytes are produced which remember the antigenic site for the measles virus so it can be destroyed before it causes disease next time it is encountered.

what is a pathogen that does not have a consistent antigenic site?

the common cold virus, so this cannot be recognised by memory cells by subsequent encounters

what is the process of antibody mediated (humoural) immunity?

• B lymphocytes are in the lymphoid tissue

• APC which has engulfed and destroyed pathogens, presets the antigenic site for the pathogen on its surface.

• APC presents the antigen to a B-cell with a matching receptor. The B-cell becomes sensitised, enlarges and divides, producing more sensitised B-cells

• Most B-cells becoming plasma cells

• The plasma cells produce antibodys specific for the antibody originally presented by the APC

• the antibody is released, and then it is able to bid the the antigenic sites on the same pathogens as the one originally presented by the APC, neutralising the pathogen

• sensitised memory B-cells remain in circulation, so that the response proceeds more quickly if pathogen is encountered again

when an APC destroys a pathogen where does it present the antigenic site?

on its surface

antibody mediated (humoural) immunity involves the production and release of…

antibodies into the blood and the lymph, providing resistance to viruses, bacteria, ad bacterial toxins before these micro-organisms or substances enter the body cells

(regarding B-cells) Lymphoid tissue contains what?

thousands of B-cells, each type has a receptor for a particular antigen and, therefore is capable of responding to a specific antigen

when and APC presents the antigen to a specific B-cells, the B-cells…

are activated.

during antibody mediated immunity APC also presents the antigens to what.… (and dont say a freaking B- cell)

helper T cells, leading to the release of cytokines

what are cytokines?

they are small proteins that are released in response to antigens and act as messages in the immune response

what do cytokines do?

cytokines cause the helper T-cells to clone themselves to release different cytokines that activate the B-cells

what happens when a B-cell is activated?

they enlarge and divide into a group of cells called a clone. Most of this clone becomes plasma cells, which secrete a specific antibody capable of attacking the active site of an antigen.

what do the antibodies do one secreted by the b-cells

these antibodies circulate in the blood, lymph and extracellular fluid to reach the site of invasion of micro-organisms or foreign material.

as most of the clone becomes plasma cells, what happens to the rest of them?

the remaining b-cells of the clone become memory cells. they spread to all body tissues to allow the response to occur more rapidly shroud the antigen enter the body again

when the clone becomes plasma cells, what can those plasma cells do?

they are able to secrete antibodies so that they can neutralise antigens

where are B-cells made and matured?

in the bone marrow

B-cells have thousands of what?

Each B-cell has thousands of unique receptors on its surface, and these receptors are specific to a particular antigen. This diversity allows the immune system to recognize and respond to a wide range of foreign invaders. When an antigen binds to a B-cell receptor, it triggers the B-cell to differentiate into plasma cells and memory cells. Plasma cells produce and secrete antibodies that can neutralize or eliminate the antigen, while memory cells provide long-lasting immunity by quickly responding to future encounters with the same antigen.

B-cells provide antibodies against pathogens such as… that have not…

such as viruses, bacteria, and some toxins that have not yet entered body cells

what is the primary response?

this is the first exposure to an antigen. The body’s immune system usually responds fairly slowly, often taking several days to build up large amounts of antibodies.

why does it take the body several days for an immune response after a primary repose/ exposure

this is because it takes time for B-cells to multiply and differentiate into plasma cells and secrete antibodies

what happens when the levels of antibodies reach its peak during the primary response?

it begins to decline. However a primary response leaves the immune system with a memory of the particular antigen (therefore symptoms occur and then are overcome)

what is the secondary response?

it is the second/ subsequent exposure to the same antigen, response is much faster due to memory cells recognising the antigen more quickly. therfore plasma cells can form very quick, and antibody levels in the blood plasma increase rapidly to a higher level that lasts longer This response can be so quick antigen has little opportunity to exert any noticeable effect on the body

which response is quicker and lasts longer, primary or secondary?

seccondary

how do antibodies work?

specific antibody is produced in response to the specific antigen for a specific pathogen after it invades. The antibody binds to the antigenic site on the pathogen, neutralising it.

what are the ways in which an antigen can be neutralised by an antibody?

• the antibody binds to the surface of a pathogen to prevent them from entering cells and causing damage.

• To coat bacteria so they are more easily consumed by phagocytes

• sticking multiple pathogens together called aggulation

• dissolve organisms

• react with soluble agents to make them insoluble and therfore more easily consumed by phagocytosis

• inactivate foreign enzymes or toxins by combining with them to inhibiting their reactions with other cells or compounds, leading to their breakdown

what is another name for cell mediated immunity?

T-cell immunity

what does cell mediated immunity do?

it provides resistance to thee intracellular phase of bacterial and viral infections. it is important in fighting whole cells and therfore providing resistance to fog, ad parasites ad rejecting forge tissue implants. it also appears to be important in fighting cancer cells

what diseases are taken out by cell mediated immunity?

tuberculosis and legionnaires disease (severe form of phenomena) as they specialise in invaded and replicating inside hosts own cells. therfore making them particularly difficult to overcome

what type of lymphocytes are responsible for cell mediated immunity?

T-lymphocytes

how and where do T-lymphocytes become activated/ sensitised ?

occurring in the same lymphoid tissue and B-cells but they occupy different areas. Like B-cells, there are thousands of types of T-cells, each type responds to only one particular antigen. When a foreign antigen such as a virus or bacterium enters the body, the antigen presenting cells present the antigen to a particular type of T-ccelll, then they become activated/ sensitised.

what happens after T-cells become activated/ sensitised

the sensitised T-cells enlarge ad divided each giving rise to a clone. some cells of the clone remain in the lymphoid tissue as memory cells, which are able to quickly recognise the original invading antigen (if infection again) These memory cells will initiate a much faster response to th second and subsequent infections.

what is a clone of T-cells?

it is a group of identical T-cells

cell mediated immunity deals with what kind of pathogens?

bacteria and viruses that are able to replicate in a cell. They also deal with foreign/ abnormal cells

• fungi

• parasites

• tissue transplant infection

• fighting cancer cells

where are T-lymphocytes made and where do they mature

they are made in bone marrow and mature in the thymus

what is the process of cell mediated immunity

• T-cells in lymphoid tissue

• APC has engulfed pathogen and presents antigen to one type of T-cell

• T-cell is sensitised, enlarges, and divided

• Many clones of the T-cell are produced, sensitised for the antigen that was presented

• These sensitised cells can be Killer T cells, Helper T cells, Supressed T cells and Memory T-cells

what is another name for Killer T-cells?

cytotoxic cells

what do killer T cells do?

cells that are infected with a pathogen have. markers on their surface, the killer T cells migrate to the site of infection. They attatch to the invading cells and secrete a chemical that will destroy the antigen, and then go to search for more antigen

what do helper T cells do?

they bind to antigen on APCs, and stimulate the secretion of cytokines that;

• attract lymphocytes to the infection site which becomes sensitised and activated thus intesifies responses

• attracts macrophages to place of infection so macrophages can destroy the antigen by phagocytosis

• they intsnsify the phagotic activity of macrophages

• promote the action of killer T cells

helper T cells are important in both…

antibody and cell mediated immunity

what do cytokines do?

the Helper T cells secrete substance that sensitises more lymphocytes, attract more macrophages and enhance their activity.

what do suppressor T- cells do?

they act when immune become excessive or the infection has been felt with successfully. They release substances that inhibit T and B cell activity. Therfore slowing down the immune response. They also stop the activity/ action of killer T cells once infected cells have been destroyed.

what do memory T cells do?

they remain sensitised to the specific pathogen, in circulation ad tissues, so that future responses to the pathogen are much more rapid.