Immunity Notes Flashcards
For a micro-organism to be pathogenic it must:
-enter host
-colonise host
-evade host defences
-cause damage to host tissues
Define the barriers preventing entry
1st- non specific
PHYSICAL
-skin
-reflexes, eg sneezing, coughing, blinking
CHEMICAL
-sebum
-tears
-HCL acid
2nd- non specific
-Inflammatory responses
-phagocytosis
-blood clotting
3rd- specific response- response tailored to the pathogen
-Immune response- active and passive immunity
-T and B Lymphocytes involved
-Long term
What is the 1st Defence Line
Natural barriers to prevent infection entry
Outline the function of the skin in defending the human body against bacterial infection
-tough physical barrier which pathogens can’t penetrate
-produces sebum (pH5.4) to kill bacteria
-pathogens only enter if the skin is cut
Function of MUCUS
-produced by goblet cells, cover epithelial linings of respiratory tract, alimentary, urinary and genital tracts
-traps micro-organisms and prevents entrance
-Cilia (tiny hairs) sweep mucus and trapped pathogens up the trachea
Outline the function of Lysozomes
-anti-bacterial (hydrolytic enzyme which digests cell walls of bacteria)
-Found in body secretions, such as tears, saliva and sweat
Outline the function of Tears
Contain Lysozomes, which are anti-bacterial and digest cell walls of bacteria
Outline the function of Hydrochloric Acid
-in stomach (gastric juice), kills bacteria in food and water consumed
-the low pH denatures enzymes of the pathogens
Explain the Inflammatory Response as the 2nd line of defence (non specific)
-Rapid
-CAPILLARIES- become leaky and plasma seeps out
-Inflamed parts are SWOLLEN with puss containing phagocytes, dead pathogens and cell debris
-Area is red (increased blood flow in area) and hot (raised temps denature enzymes in the pathogen to reduce infection).
Describe the process of Phagocytosis
- Phagocytes (polymorphs and macrophages) are attracted to the pathogen by chemicals it produces.
- The membrane of the phagocyte SURROUNDS (INVAGINATES) and ENGULFS the pathogen
- The invaginated membrane forms a vesicle called a PHAGOSOME around the pathogen
- Lysozomes containing HYDROLYTIC ENZYMES move towards the phagosome and FUSE with it
- The enzymes are released into the PHAGOSOME and they HYDROLYSE the pathogen.
- The soluble DIGESTED products are ABSORBED into the cytoplasm of the phagocyte or may be excreted by EXOCYTOSIS.
Describe the IMMUNE RESPONSE as the 3rd line of defence
-Body’s reaction to a specific foreign ANTIGEN/ pathogen. Involves production of cells and chemicals to defend the body
-Involves the body being able to recognise ‘self’ and ‘non-self’ tissue
Define as Antigen
Antigens are any chemical, which causes the production of specific and complementary antibodies (immune response)
-antigens can be toxins produced by pathogens or the proteins, glycoproteins and polysaccharides in their membranes.
Define as Antibody
They are globular protein molecules produced in response to a particular foreign antigen
-they are SPECIFIC and COMPLEMENTARY to particular antigens and which can react with antigens leading to their destruction.
Describe the specific immune response
-Involves LYMPHOCYTES (white blood cell).
-Pathogens carry molecules on outer surface, called antigens, that are recognised as foreign/ non self. They initiate the immune system.
-Different pathogens have different antigens- SPECIFIC
-For each antigen on the surface, a Lymphocyte carries a special protein receptor on the cell surface membrane, which has a COMPLEMENTARY SHAPE
-The complementary shape ensures a SPECIFIC RESPONSE
-From a young age, different lymphocytes are produced from stem cells in the bone marrow.
-Each carries a specific membrane receptor which can respond to different non self antigens if encountered in the future.
-Therefore, the body can respond to any type of pathogen hat enters the body
-No Lymphocytes can respond to pathogens/ molecules on the CSM of the individuals own cells (self antigens).
Describe the B-Lymphocyte
(B-Cells)
-Produced- stem cells in the bone marrow
-Mature- bone marrow
-Type of Immune Response- Antibody mediated Immunity
-Nature of Immune Response- secrete antibodies which counter the antigens found in body fluids (blood/ tissue fluid)
-respond to bacterial/ viral infection
Describe the T Lymphocytes
(T-Cells)
-Produced- bone marrow
-Mature- thymus gland
-Type- cell mediated Immunity
-Nature- they attack infected body cells with the antigen presented on the surface.
-Respond to body cells infected by viral infection
Where do Lymphocytes move to await activation
-Lymphoid tissue
Describe the activation of the Lymphocyte
-Involves the LYMPHOCYTE COMING INTO CONTACT WITH AN ANTIGEN that its receptor can recognise
-Infected cells display antigens on their surface
-This is the only way T-Lymphocytes can detect the antigen.
-When they have made contact with the antigen, the Lymphocytes become SENSITISED (activated).
-A SPECIFIC GENE is ACTIVATED for the production of antibodies in B cells and for the production of different T cells
-The Lymphocytes then DIVIDE by MITOSIS (cloned)
-This takes time, there is a DELAY of a few days between the contact with the antigen and the cloning of the required Lymphocyte.
-During this wait time, the person will SUFFER FROM THE DISEASE caused by the pathogen.
Where do B-Lymphocytes respond to antigens
On the surface of the actual pathogen
What Lymphocytes does antibody mediated immunity target
B- Lymphocytes
Describe the process of Antibody- Mediated Immunity
- Bacteria/ virus found in body fluids (blood) invades the body
- Specific antigens SENSITISE (activate) specific B- Lymphocytes
- B- Lymphocytes are activated when SPECIFIC BINDING SITES attach to antigens.
- Activated B- Lymphocytes RESPOND by DIVIDING BY MITOSIS, forming a CLONE (during this time there’s no immediate antibody response and delay allows pathogen to cause ILLNESS).
- PLASMA CELLS (short lived) are formed, which synthesise and secrete large numbers of ANTIBODIES
- Antibodies NEUTRALISE the pathogen- result in an ANTIGEN-ANTIBODY REACTION.
- MEMORY CELLS also produced from the initial clone. They don’t produce antibodies but persist over a very LONG TIME.
- On infection from the same pathogen, the memory cells divide, producing vast numbers of plasma cells which synthesise and SECRETE ANTIBODIES RAPIDLY.
- Such is the rapidity of the response, the host DOES NOT SUFFER from the symptoms of infection again- SECONDARY IMMUNE RESPONSE
Where do T-Lymphocytes respond
T-Lymphocytes only respond to antigens when present on the surface of a body cell
What type of Lymphocyte does cell mediated immunity target?
Cell-mediated Immunity
Describe the process of Cell Mediated Immunity
- BODY’S OWN CELLS change due to the presence of non-self material inside, known as ANTIGEN-PRESENTING CELLS.
-they may be macrophages that have engulfed a pathogen and present some of the pathogens antigens on their CSM.
-any body cells that have been invaded by a virus and viral antigens are presented on the CSM
-cancer cells that present abnormal antigens on the CSM - T-Lymphocytes have SPECIFIC RECEPTORS on the CSM which attach to COMPLEMENTARY viral ANTIGENS on the CSM on the antigen-presenting cell.
- T-Lymphocytes become ACTIVATED (sensitised) and divide by Mitosis- clone
- The cloned cells develop into
-killer T-cells
-Helper T-cells
-Memory cells
