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Humun Immunodeficiency Virus

Humun Immunodeficiency Virus

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On the outside of the HIV and lip envelopes, embed in which are peg-like attachment proteins. Inside the envelope the protein layer called the capsid that contains 2 single strands of RNA as well as some enzymes.

One of these enzymes is Reverse transcriptase, this catalyses the production of DNA and the RNA. Transcriptase does the opposite effect of this. The presence of these enzymes results in the ability to produce DNA from RNA.

HIV, as the name suggest, is a virus. As a result, it cannot replicate itself, instead it uses genetic material to instruct the host’s cells biochemical mechanisms to produce the relevant components to produce a new HIV.

 

  • Upon infection, the HIV enters the bloodstream thus gaining access to circulate around the entire body.
  • A protein found on the HIV readily binds to cells around the body, though frequently to the T-cells.
  • The protein capsid fuses itself with the cell-surface membrane of the cell it has attached to.
  • The enzymes of the HIV enter into the cell/helper T cell.
  • HIV reverse transcriptase converts the virus’s RNA into DNA.
  • The new DNA molecule is then transferred into the cells/T cells nucleus where it is inserted into its own DNA
  • The HIV’s DNA in the nucleus creates mRNA using the cell’s enzymes. This mRNA contains instructions for making new viral proteins and the RNA to go into the new HIV particles
  • The HIV particles break off the T-helper cells with a piece of its cell surface membrane surrounding them which forms their lipid envelope.

Once infected with HIV a person is said to be HIV positive, however the replication of HIV often goes dormant, sometimes becoming reactivated and leading to AIDS many years later.

 

Vaccinations

Vaccinations

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Passive Immunity

  • Produced by the introduction of antibodies into individuals from an outside source
  • No direct contact with the pathogen or its antigens is necessary to induce immunity; immunity is acquired immediately
  • As the antibodies are not being produced by the individuals themselves, the antibodies are not replaced when they are broken down
  • No memory cells are formed and so there is no lasting immunity
  • Examples include antivenom or in the antibodies carried from the mother to the foetus

 

Active Immunity

  • Produced by stimulating the production of antibodies by the individuals own immune system
  • Direct contact with the pathogen or its antigen is required
  • Immunity takes time to develop
  • It is generally long lasting through the production of memory cells
  • Active immunity has two types:
  • Natural active immunity: Results from an individual becoming infected with a disease under normal circumstances. The body produces its own antibodies and may continue to so for many years
  • Artificial Active Immunity: Forms the basis of vaccinations, it involves inducing an immune response in an individaul without them suffering the symptoms by injecting dead/inactive pathogens into the patient’s body

 

Antigenic Variability

  • Antigens on the cell surface of a pathogen are used to activate the immune system. However, these antigens can change, through antigenic variability which occurs as a result of the change in the genes through mutations
  • The changes to the antigens means that when you are infected with the pathogen, the pathogen cannot be identified by the immune system and is therefore treated as a primary immune response (as it is considered new)
  • Antigenic variability is therefore harder to vaccinate against as they are always changing
  • Influenza virus and HIV are examples of pathogens which have antigenic variability, hence why flu vaccinations have to be had every year.

 

Humoral Cells

Humoral Cells

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Humoral immunity is the use of antibodies to rid of the pathogen. (humour meaning body fluids i.e. blood as that’s where the antibodies are transported in). In the body, there are over 10 million different B cells, each with a different variable region on its membrane bound antigens that are specific to one type of antigen. B cells do not leave the lymph nodes, rather their antibodies do and travel to the required areas via the circulatory system.

  1. The pathogen is taken up by the B-cells
  2. The B-cells breaks the pathogen down and presents its antigens on the cell surface membrane as processed antigens, as well as antibodies. These antibodies are membrane bound, meaning that they are fixed to the membrane of the B-cell. These antibodies are unique to each B-cell.
  3. T helper cells attach to the processed antigens on the B-cells resulting in them becoming activated
  4. The B-cells now divide through mitosis to produce a plasma cell that produce antibodies with the correct variable region for the antigen on the pathogen. Plasma cells only live for a few days but however
  5. The antibodies produce attach themselves to the antigen on the pathogen and destroy them. This is a primary immune response.
  6. Some of the B cells then go onto develop into memory cells which remain in the body for decades with the ability to produce antibodies rapidly in the event of reinfection by the same pathogen. This is a secondary immune response.

 

Cell Mediated Immunity

Cell Mediated Immunity

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Cell mediated immunity is the result of T lymphocytes or T-cells. T cells are produced in the thymus gland, they respond to both pathogen cells but also the body’s own cells altered by viruses or cancer and to transplanted tissues. T-cells will only respond to the presence of an antigen.

 

  1. The pathogen enters the body after passing through the bodies physical barriers (e.g. skin)
  2. Some of the pathogens are engulfed by the phagocytosis phagocytes in phagocytosis and gets into the body’s tissues
  3. Phagocytes break the pathogen down using enzyme and presents its antigens on the phagocytes cell membrane for the T cells
  4. The receptors on the T helper cells then takes the antigen from the phagocyte
  5. This activates the T cells to clone through mitosis to produce
  • Memory cells: cells which remain in the body that lay dormant for the most part until the same pathogen’s
    antigens are found again the in the body in which the memory cells are able to reactivate
    and produce the antibodies that worked last time. Memory cells are specific to the one type of pathogen.
  • Cytotoxic T cell (Tc cells) which can make holes in the cell membrane of the pathogen causing it to break down
  • Stimulates the phagocytes to engulf the pathogens
  • Stimulate B-cells to divide

 

 

Antibodies
Immune System

Antibodies

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Antibodies are produced by the B-lymphocytes, they are made up of proteins. They are produced as a result of foreign matter found within the body. Antibodies bind to the complimentary antigens found on the cell surface membranes of a non-self cell.

Antibody Structure

 

Antibodies are made up of four polypeptide chains, the chains of one pair are long and are called heavy chains. The other chain is smaller and are called the antigen-antibody complex. The binding site is different on different antibodies and is therefore called the variable region.

Each Binding site consist of a sequence of amino acids that form a specific 3D shape that binds directly to a specific antigen. The rest of the antibody is a constant region, this binds to the receptors on sells such as B-cells. The light chain is attached to the heavy chain by a disulphide bond.

Antibodies are polyclonal as they are clones of one another derived from the source cell, the             B-lymphocytes

Monoclonal Antibodies

  • Each bacterium will have many different antigens
  • Each antigen also produces B-cells to produce different antibodies
  • The B-cells also produce clones which produces these different antibodies
  • They are polyclonal antibodies
  • If a single type of antibody is produced outside the body, they are called monoclonal antibodies

 

Producing Monoclonal Antibodies

 

  • A mouse is exposed to the non-self material against which an antibody is required
  • The B-cells in the mouse then produce a mixture of antibodies, which are extracted from the spleen of the mouse
  • To enable these B-cells to divide outside the body detergent is added to the mixture to break down the cell-surface membranes of both types of cells and enables them to fuse together. The fused cells are called hybridoma cells
  • The hybridoma cells are separated under a microscope and each single cell is cultured to form a clone
  • Any clone producing the required antibody is grown on a large scale and the antibodies are extracted from the growth medium
  • Because these antibodies come from a clone formed from a single B-cell, they are called monoclonal antibodies
  • As they are produced by mice they need to be humanised.

 

Uses of Monoclonal Antibodies

  1. Pregnancy Testing
  2. Cancer treatments
  3. Diabetes
  4. Crohn’s disease
  5. Multiple sclerosis
  6. Diagnosis

Monoclonal Antibodies and Cancer

Monoclonal antibodies can be bind with chemo-toxins. In binding to cancer cells, they can administrate the toxin to it, and therefore damage it. The advantage to this method is it only harms the cancer tissues and not healthy cells.

Immunity

Immunity

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Pathogens are inhibited into entering into the body by various mechanisms such as:

 

  • The eye has tears and eyelashes
  • Respiratory system having mucus and cilia lining the tracts
  • The skin is a physical barrier including antibacterial properties of sebum and sweat

 

Immune System

The immune system is a collection of cells tissues and organs with mechanisms that defend an organism against the pathogen and other foreign substances. An immune system response in the body is a complex series of specific and non-specific processes involving a range of cells and chemicals.

Non-Specific

 

  • Non-specific immune response is the ‘general’ response to pathogen.
  • For example the physical barriers such as the skin and mucus.
  • Phagocytosis engulfs the pathogen regardless to what the pathogen is
  • The response is immediate as they are always present

 

Specific

 

  • Specific immune response is far flower however is unique to each pathogen
  • Cell mediated response in the T-cells
  • Humoral response in B-lymphocytes

 

Antigens

 

  • An antigen is any part of an organism or substance that is recognised as a non-self (foreign) by the immune system and stimulates an immune response
  • Antigens are usually proteins that are part of the cell surface membrane or cell wall
  • The presence of a non-self antigen causes the production of an antibody as part of the body’s defence system

 

Lymphocytes

 

  • Lymphocytes are white blood cells
  • They are produced by stem cells

 

B-lymphocytes

  • Matured in the bone marrow
  • Produces antibodies and antitoxins
  • Responds to foreign materials outside body cells
  • Humoral immunity (immunity involving antibodies that are present in the body’s fluids (humour) such as blood plasma)

 

T-lymphocytes

  • Matured in the Thymus Gland
  • Responds to antigens presented by the phagocytes
  • Responds to viral infected cells and cancer
  • Associated with cell mediated immunity (immunity that involves body cells)

 

How lymphocytes recognise cells belonging to the body:

 

  • There are around 10 million different lymphocytes present at any time
  • In the foetus, these lymphocytes are constantly colliding with other cells. However infection as a foetus is rare
  • Lymphocytes will therefore collide almost exclusively with the body’s own material. Lymphocytes have receptors that exactly fit those of the body’s own cells.
  • These lymphocytes either die or are suppressed whether leaving those that might fit foreign antigens and therefore only respond to the presence of foreign materials
  • In adults lymphocytes are produced in the bone marrow only encounter self-antigens
  • Any lymphocyte that shows an immune response to the self-antigens undergo programmed cell death (Apoptosis)

 

Vaccinations

Vaccinations

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Passive Immunity

 

  • Produced by the introduction of antibodies into individuals from an outside source
  • No direct contact with the pathogen or its antigens is necessary to induce immunity; immunity is acquired immediately
  • As the antibodies are not being produced by the individuals themselves, the antibodies are not replaced when they are broken down
  • No memory cells are formed and so there is no lasting immunity
  • Examples include antivenom or in the antibodies carried from the mother to the foetus

 

Active Immunity

 

  • Produced by stimulating the production of antibodies by the individuals own immune system
  • Direct contact with the pathogen or its antigen is required
  • Immunity takes time to develop
  • It is generally long lasting through the production of memory cells
  • Active immunity has two types:
  • Natural active immunity: Results from an individual becoming infected with a disease under normal circumstances. The body produces its own antibodies and may continue to so for many years
  • Artificial Active Immunity: Forms the basis of vaccinations, it involves inducing an immune response in an individaul without them suffering the symptoms by injecting dead/inactive pathogens into the patient’s body

 

Antigenic Variability

 

  • Antigens on the cell surface of a pathogen are used to activate the immune system. However, these antigens can change, through antigenic variability which occurs as a result of the change in the genes through mutations
  • The changes to the antigens means that when you are infected with the pathogen, the pathogen cannot be identified by the immune system and is therefore treated as a primary immune response (as it is considered new)
  • Antigenic variability is therefore harder to vaccinate against as they are always changing
  • Influenza virus and HIV are examples of pathogens which have antigenic variability.

 

Antibodies

Antibodies

by My 0 Comments

Antibodies are produced by the B-lymphocytes, they are made up of proteins. They are produced as a result of foreign matter found within the body. Antibodies bind to the complimentary antigens found on the cell surface membranes of a non-self cell.

Antibody Structure

Antibodies are made up of four polypeptide chains, the chains of one pair are long and are called heavy chains. The other chain is smaller and are called the antigen-antibody complex. The binding site is different on different antibodies and is therefore called the variable region.

Each Binding site consist of a sequence of amino acids that form a specific 3D shape that binds directly to a specific antigen. The rest of the antibody is a constant region, this binds to the receptors on sells such as B-cells. The light chain is attached to the heavy chain by a disulphide bond.

Antibodies are polyclonal as they are clones of one another derived from the source cell, the             B-lymphocytes

Monoclonal Antibodies

 

  • Each bacterium will have many different antigens
  • Each antigen also produces B-cells to produce different antibodies
  • The B-cells also produce clones which produces these different antibodies
  • They are polyclonal antibodies
  • If a single type of antibody is produced outside the body, they are called monoclonal antibodies

 

Producing Monoclonal Antibodies

 

  • A mouse is exposed to the non-self material against which an antibody is required
  • The B-cells in the mouse then produce a mixture of antibodies, which are extracted from the spleen of the mouse
  • To enable these B-cells to divide outside the body detergent is added to the mixture to break down the cell-surface membranes of both types of cells and enables them to fuse together. The fused cells are called hybridoma cells
  • The hybridoma cells are separated under a microscope and each single cell is cultured to form a clone
  • Any clone producing the required antibody is grown on a large scale and the antibodies are extracted from the growth medium
  • Because these antibodies come from a clone formed from a single B-cell, they are called monoclonal antibodies
  • As they are produced by mice they need to be humanised.

 

Uses of Monoclonal Antibodies

  1. Pregnancy Testing
  2. Cancer treatments
  3. Diabetes
  4. Crohn’s disease
  5. Multiple sclerosis
  6. Diagnosis

Monoclonal Antibodies and Cancer

Monoclonal antibodies can be bind with chemo-toxins. In binding to cancer cells, they can administrate the toxin to it, and therefore damage it. The advantage to this method is it only harms the cancer tissues and not healthy cells.

Phagocytosis

Phagocytosis

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  • Large particles (like those of bacteria) can be engulfed through the process of phagocytosis. The white blood cells which carry out this process are the Phagocytes (Macrophages).
  • Phagocytosis is a non-specific immunity as it simply engulfs pathogens, not caring what they are.

  • Phagocytes travel in the blood but can move out of the blood vessels into other tissues
  • Chemical products of pathogens, dead or damaged cells or abnormal cells act as attractants causing phagocytes to move towards these pathogens. (chemotaxis)
  • Phagocytes have several receptors on their cell surface membrane that recognise and attach to chemicals on the surface of the pathogen.
  • They engulf the pathogen to form a vesicle, known as a phagosome
  • Lysosomes moves towards the vesicle and fuse with it
  • Enzymes called Lysozymes are present within the lysosome. These lysozymes destroy ingested bacteria by hydrolysis of their cell walls. The process is the same as that for digestion of food in the intestine, namely the hydrolysis of larger, insoluble molecules into smaller soluble ones
  • The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte
  • The phagocyte also presents the antigens of the pathogen it has for the T-cells for their specific response

 

Immunity

Immunity

by My 0 Comments

Pathogens are inhibited into entering into the body by various mechanisms such as:

  • The eye has tears and eyelashes
  • Respiratory system having mucus and cilia lining the tracts
  • The skin is a physical barrier including antibacterial properties of sebum and sweat

Immune System

  • The immune system is a collection of cells tissues and organs with mechanisms that defend an organism against the pathogen and other foreign substances.
  • An immune system response in the body is a complex series of specific and non-specific processes involving a range of cells and chemicals.

Non-Specific

  • Non-specific immune response is the ‘general’ response to pathogen.
  • For example the physical barriers such as the skin and mucus.
  • Phagocytosis engulfs the pathogen regardless to what the pathogen is
  • The response is immediate as they are always present

Specific

  • Specific immune response is far flower however is unique to each pathogen
  • Cell mediated response in the T-cells
  • Humoral response in B-lymphocytes

Antigens

  • An antigen is any part of an organism or substance that is recognised as a non-self (foreign) by the immune system and stimulates an immune response
  • Antigens are usually proteins that are part of the cell surface membrane or cell wall
  • The presence of a non-self antigen causes the production of an antibody as part of the body’s defence system

Lymphocytes

  • Lymphocytes are white blood cells
  • They are produced by stem cells

B-lymphocytes

  • Matured in the bone marrow
  • Produces antibodies and antitoxins
  • Responds to foreign materials outside body cells
  • Humoral immunity (immunity involving antibodies that are present in the body’s fluids (humour) such as blood plasma)

T-lymphocytes

  • Matured in the Thymus Gland
  • Responds to antigens presented by the phagocytes
  • Responds to viral infected cells and cancer
  • Associated with cell mediated immunity (immunity that involves body cells)

How lymphocytes recognise cells belonging to the body:

  • There are around 10 million different lymphocytes present at any time
  • In the foetus, these lymphocytes are constantly colliding with other cells. However infection as a foetus is rare
  • Lymphocytes will therefore collide almost exclusively with the body’s own material. Lymphocytes have receptors that exactly fit those of the body’s own cells.
  • These lymphocytes either die or are suppressed whether leaving those that might fit foreign antigens and therefore only respond to the presence of foreign materials
  • In adults lymphocytes are produced in the bone marrow only encounter self-antigens
  • Any lymphocyte that shows an immune response to the self-antigens undergo programmed cell death (Apoptosis)