Why do we have an immune system?

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Why do we have an immune system?
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Immune system diseases
Non specific immunity
Disease survival mechanisms
Physical chemical barriers
Infectious Disease
Inflammatory Response
Transmission
Epidemiology
Non-specific Cellular response
Specific immunity
Public Health
Vaccination
phagocytes
NK cells
Immunological surveillance
Clonal Selection theory
T cells
B cells
Big picture
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Cells of the Immune System many cells we will
look specifically at these ..
Bone graft
Macrophage
Mast cell
Eosinophil
Erythrocytes
Marrow
Basophil
Monocyte
Megakaryocyte
Bone
Hematopoieticstem cell
Multipotential stem cell
Myeloid progenitor cell
Neutrophil
Platelets
Lymphoid progenitor cell
Dendritic cell
T lymphocyte
B lymphocyte
Natural killer cell
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The human body has the capacity to protect itself
against pathogens, some toxins and cancer cells
through the immune system

• GLOSSARY TERMS
• PATHOGEN DISEASE CAUSING ORGANISMS
• TOXINS POISONS PRODUCED BY ORGANISMS
• IMMUNITY BODYS ABILITY TO RESIST INFECTION BY
  A PATHOGEN OR DESTROY THE ORGANISM IF IT SUCCEEDS

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Learning outcomes

• Distinguish between the non-specific and specific
  immune system
• Identify the three lines of defence
• Explain the non-specific defences

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Immune system organisation

• SPLIT INTO 2 AREAS
• NON SPECIFIC AND SPECIFIC
• NON-SPECIFIC IMMUNITY WORKS AGAINST ANY TYPE OF
  DISEASE-CAUSING AGENT
• SPECIFIC IMMUNITY WORKS AGAINST A PARTICULAR
  PATHOGEN

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Non-specific physical barriers

• EPITHIAL cells
• The first line of defence against infection.
• Line the surfaces and cavities of the entire
  body.
• Form sheets/ layers of closely packed cells.
• SECRETIONS
• Some Epithelial cells produce secretions such as
  enzymes, hormones and lubricating fluids that can
  defend against infection.
• Mucus traps dirt and germs, preventing them from
  entering the blood.
• Various glands produce antimicrobial secretions
  that help kill microbes.

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Other physical defences

• TINY HAIRS AT THE ENTRANCE TO THE NOSE.
• COUGH AND SNEEZE REFLEXES.
• FRIENDLY
• BACTERIA.

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Non-specific immunity

• First line of defence are physical and chemical
  barriers

Line of defence Specific (s) or non-specific (ns) Mechanism employed Function
1st NS Skin barrier Epithelial cells intact
1st NS Mucus Cilia Traps microbes in respiratory and gastrointestinal tract Remove microbe by sweeping
1st NS Acid Contains hydrochloric acid at pH 1.5 - 2.5 which has a disinfecting action on the stomach wall and contents.
1st NS Sweat and sebaceous Low pH inhibits microbial growth
1st NS Saliva and tears Enzymes lysozyme digests bacterial walls so it destroys them
Remember lysozyme - ZZZZZ for sleep in your eye!
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Immune system organisation

• Second line of defence is the Inflammatory
  response
• This occurs if the first line are breached, by a
  cut/ piercing or an invasion of an infectious
  organisms

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Immune system organisation

• Second line of defence is the Inflammatory
  response
• This occurs if the first line are breached, by a
  cut/ piercing or an invasion of an infectious
  organisms

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• Mast cells? histamine ?vasodilation and
  increased capillary permeability ? secrete
  cytokines ? phagocytosis ? complement /
  antimicrobial proteins ? clotting and tissue
  repair

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phagocytosis
A phagocyte is motile (moves towards pathogen
when chemicals detected or antigens). It then
engulfs pathogen (endocytosis) forming a
phagocytic vesicle (vacuole) which merges with a
lysosome. Lysosomes contain digestive enzymes,
which disposes of the pathogen and released by
exocytosis. The phagocyte releases more
cytokines positive feedback
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Natural killer cells
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1. Protein from NK cell inserts a pore into the
target cell membrane
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Outer membrane on target cell
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protease
3. Signal relayed and genes switched on
2. Signal molecule from NK enters cell
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vital cell protein
4. suicide proteins made
5. suicide protein function to make degradative
enzymes (protease / DNAase). Destroying vital
proteins/DNA
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Useless fragments of DNA
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DNAase
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Useless fragments of protein
DNA
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Natural killer (NK) cells

• FINAL NON-SPECIFIC DEFENCE
• FOR VIRUS AND TUMOUR CELLS PREDOMINANTLY
• DISTINCT CLASS OF LYMPHOCYTES WHICH CAN WORK WITH
  ANTIBODY-DEPENDENT CELLULAR CYTOTOXITY HOWEVER
  THEY ARE NOT SPECIFIC WILL ATTACK CELLS (DECIDE
  SELF/FOREIGN BY LACK OF SELF ANTIGEN (MHC).
• A PORE RELEASED FROM NATURAL KILLER (NK) CELL
• NK CELL THEN RELEASES SIGNALLING MOLECULES
• THIS SIGNALS GENETIC CONTROL OF BOTH SELF
  DESTRUCTIVE ENZYMES BEING RELEASED AND DNA /
  VITAL PROTEIN BREAKDOWN
• PROCESS OF CELL SUICIDE, PROGRAMMED CELL DEATH
  IS CALLED APOPTOSIS

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NK CELLS

• Secondary affect which links to the specific
  immune system is both NK cells and phagocytes
  secrete cytokines (interleukins ) that serve to
  stimulate the specific immune response through
  the activation of T cells

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Natural killer cells
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1. Protein from NK cell inserts a pore into the
target cell membrane
1
Outer membrane on target cell
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protease
3. Signal relayed and genes switched on
2. Signal molecule from NK enters cell
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vital cell protein
4. suicide proteins made
5. suicide protein function to make degradative
enzymes (protease / DNAase). Destroying vital
proteins/DNA
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Useless fragments of DNA
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DNAase
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Useless fragments of protein
DNA
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Complement system

• THE PRESENCE OF BACTERIA AT THE SITE OF INFECTION
  STIMULATES ANTIMICROBIAL PROTEINS KNOWN AS
  COMPLEMENT TO ARRIVE AT THE SITE OF INFECTION.
• THE COMPLEMENT SYSTEM HELPS THE BODY TO RID
  ITSELF OF INFECTION BY AMPLIFYING THE IMMUNE
  RESPONSE.

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Cytokines ....

• Made by damaged tissue / white blood cells
• Enhance migration of phagocytes (chemotaxins -
  chemoattractants) which engulf/digest pathogen
  and release more cytokines
• Deliver antimicrobial proteins faster which
  amplifies immune response
• Deliver blood clotting chemicals (complement)
  which seals the wound and helps tissue repair
• Have a dual purpose not only in the non-specific
  defence but also specific defence system by
  triggering lymphocytes (next lesson)

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Clotting system

• The final stage of inflammation is tissue repair.
• What do you remember from unit 2?
• What molecules involved?
• What is prothrombin / fibrinogen?

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Non-specific immunity

• second line of defence are inflammation cascade
  and cellular responses

Line of defence Specific (s) or non-specific (ns) Mechanism employed Function
2nd NS Inflammatory response Inflammatory response initiated by histamine and serotonin release from basophils/mast cells attracts phagocytes to infected region. Reduces spread of infection throughout organism.
2nd NS Cellular response of phagocytes (phagocytosis) Ingestion and digestion of foreign particles/microbes by neutrophils, eosinophils, monocytes and macrophages.
2nd NS Cellular response of natural killer cells (NK cells) Attack virus and cancer cells by releasing molecule which forms a pore in target cells membrane which signals apoptosis by self destroying enzymes
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Summary slide

• Non-specific defences
• Physical defences
• Epithelial cells on the body surface and cavity
  linings form a physical barrier
  (skin/trachea/oesophagus etc.)
• chemical defences
• Mucus membranes secrete sticky mucus trapping
  microorganisms
• Acid from epithelial cells in stomach destroy
  ingested microorganisms
• Skin sebaceous/sweat glands produce low pH
  secretions that are too low for most microbes to
  survive

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Summary slide

• Non-specific defences
• Inflammatory response
• Release of histamine by mast cells causes
  vasodilation and increased capillary
  permeability.
• The increased blood flow and the secretion of
  cytokines results in the accumulation of
  phagocytes and the delivery of antimicrobial
  proteins and clotting elements to the site of
  infection.

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Summary slide

• Non-specific defences
• Cellular mechanisms
• A variety of specialised white blood cells
  provide protection against pathogens.
• Phagocytes recognise surface antigen molecules on
  pathogens and destroy them by phagocytosis.
• Natural killer (NK) cells induce the pathogen to
  produce self destructive enzymes in apoptosis.
• Both Phagocytes and NK cells release cytokines
  which stimulate the specific immune response.
• Complement system amplifies this immune response.