Chapter 7: Immunity Flashcards
What is a pathogen?
A disease causing organism
What are 6 types of transmission of pathogens/viruses?
ACID VB
Contact, body fluids, droplets, ingestion, airborne, vectors
What is the difference specific and non-specific defences?
Non-specific defences work against all pathogens whilst specific defences target particular pathogens
What is the body’s first line of defence?
Non-specific defence mechanisms like your intact skin and mucous membranes and their secretions
What is the body’s second line of defence?
Non-specific defence mechanisms like phagocytic white blood cells, inflammation and fever and antimicrobial substances
What is the body’s third line of defence?
Antibodies and specialised lymphocytes called B and T cells
Name 4 protective reflexes
Coughing, sneezing, vomiting, diarrhoea
Describe the non-specific internal defence of phagocytosis
Process by which phagocytes engulf and destroy microorganisms as well as cell debris. Includes macrophages, which are large phagocytic cells that were originally leucocytes that either engulf or destroy or release killer substances.
Describe inflammation
A non-specific defence that causes swelling, redness and heat as a result of damage to the body’s tissue.
Steps of inflammation
- Mast cells stimulate and coordinate inflammation by releasing chemicals called histamine and heparin, resulting in swelling and redness in the damaged area.
- Phagocytes are attracted by chemicals released by mast cells. Macrophages and leucocytes eat microorganisms and debris is consumes by phagocytosis.
- Changed conditions in area of inflammation stimulates pain receptors so pain is felt.
- Phagocytes filled with the bacteria die and form pus
- Damaged tissues repaired by mitosis
Describe functions of histamine
Released during inflammation by mast cells. Increases blood flow to the area by vasodilation, and make walls of blood capillaries more permeable resulting in heat, swelling and redness
Describe functions of heparin
Release of heparin from mast cells prevents clotting in the immediate area of injury. Clot of fluid forms around damaged area and slows spread of pathogen
Describe characteristics of a fever
Person feels cold, vasoconstriction in skin and shivering, increased heat production then pushes the temperature up rapidly, then the person feels hot and vasodilation and profuse sweating occurs
Stages of a fever
Stages of fever
- Pathogen presence detected by leucocytes
- White blood cells accumulate and release pyrogens
- Pyrogens detected by hypothalamus
- Hypothalamus increases body temperature
- Feedback - mechanisms to increase temp e.g. shivering
What does a fever cause?
Causes:
Inhibits growth of pathogens
Denature proteins and enzymes for pathogen function
Metabolism of body occurs faster → increased repair
Describe lymphatic system
Non-specific defence
Function to collect fluids escaping from blood capillaries
Network of lymph capillaries joined to lymph vessels,
Lymph nodes located along length of lymph vessels
What do lymph nodes do?
Lymph nodes:
Lymph has cell debris, foreign particles and microorganisms
Nodes have lymph tissue and networks of fibres
Bacteria get trapped in network
Macrophages destroy particles
Lymph nodes can become swollen and sore
What are two immune responses to deal with foreign invaders?
Humoral response/antibody mediated immunity: production of antibodies by B cells
Cell mediated immunity: formation of special lymphocytes by T cells
Characteristics of B and T cells
Most lymph tissue made of B and T cells
B and T cells both produced in bone marrow
Half of cells produced in bone marrow move to thymus gland and mature into T cells
Other half stay in bone marrow to mature into B cells
What are antigens
Antigen = any substance capable of producing an immune response
If an antigen gets into the body, body will produce antibodies
Difference between non-self and self antigens
Large molecules produced by person’s own body do not cause immune response
= self antigen
Foreign compounds causing an immune response
= non-self antigen
5 classes of anti bodies
IgG - resistance against many viruses, bacteria and bacterial toxins
IgE - accelerates local inflammation
IgD - found on surface of B cells
IgM - first type secreted after antigen arrives
IgA - primarily found in glandular secretions
Describe the antibody antigen complex
- Antibody combines with antigen to form antibody antigen complex
- Active site of antigen combines with active site of antibody
- Antibody + antigen fit together like a lock and key
- Each antibody can only combine with a particular antigen - specific
Describe antibody mediated (humoral) immunity
- Humoral response begins when a foreign protein (antigen) binds to a specific B cell
- Antigen binding stimulates B cells to proliferate, forming many plasma cells
- Plasma cells make antibodies to attack and destroy a specific identified pathogen - Some B cells differentiate into long lived memory cells
- These memory cells will rapidly produce antibodies if the same pathogen enters the body again
What is the antibody mediated immunity primary and secondary response?
1st exposure to antigen - IgM is the first antibody secreted after antigen arrival
2nd exposure - IgG is secreted
How do antibodies work
- Combines with foreign body and inactivate them by inhibiting reactions
- Bind to surface of viruses to prevent them from entering cells
- Coat bacteria so they can be consumed by phagocytosis by macrophages
- Causes foreign particles to clump together = agglutination
- Dissolve the organism
Makes soluble substances insoluble to undergo phagocytosis
Describe cell mediated immunity
Is the intracellular phase of a viral and bacterial infections (e.g. cancer).
Thousands of T cells respond to a particular antigen. T cells become sensitised and enlarge to form clones of T cells and some will stay in lymphoid tissue as memory cells.
3 types of T-cells
- Killer T cells
- Helper T cells
- Suppressor T cells
