Body Defence 1 Flashcards
How does the the body deal with threats?
- Protects from pathogens
- Detects antigens
Where are pathogens found?
Found in air, food and water and micro-organisms that cause disease
What does the body detect to deal with threats?
Antigens
(toxins or other foreign substances which induce specific immune responses, especially the production of antibodies)
What factors determine an individual’s response to a pathogen?
- Prior exposure
- Genetics
- Sex ( pregnancy enters a state of
immunosuppressants) - Age (elderly and very young children have
weaker immune system) - Stress
What are the 6 exterior defences that are ‘first lines of defence’?
Skin - prevent entry
Saliva - antibacterial enzymes
Tears - antibacterial enzymes
Mucus - lining traps dirt and microbes
Stomach Acid - lop pH kills harmful microbes
‘Good’ gut bacteria - out compete bad bacteria
What are the routes that defences used to stop pathogen entry to the body?
Mucosal immunity protects internal epithelial surfaces from invading threats
Physical, chemical and immunological defences
What are the 2 primary lymphoid organs?
- The bone marrow
- The thymus
What are the 3 secondary lymphoid organs?
- Tonsils
- Lymph nodes
- the Spleen
What are the interior defence organs of immunological protection?
- Tonsils and adenoids
- Lymph nodes
- Lymphatic vessels
- Thymus
- Spleen
- Peyer’s patches
- Appendix
- Bone marrow
What does the lymphatic system do?
Circulates a clear fluid, lymph, it travels towards the heart in open circulatory system.
What is lymph?
Lymph is filtered interstitial fluid
(filtered from plasma)
How does lymph fluid circulate the body?
Circulates semi-passively depending on contractions of lymphatic vessels or compression of them - e.g. by muscle contraction
How can lymph fight infection?
Lymph transports white blood cells to fight infection
What happens when lymph passes through lymph nodes?
The lymph nodes contain lymphocytes where microbes and wastes are filtered out
What are the 3 non-specific exterior first line of defences?
Skin
Mucous membrane
Secretions
What are the 3 non-specific interior second line of defences?
Phagocytic white blood cells
Antimicrobial proteins
Inflammatory response
What are the 2 specific third line of defences?
Lymphocytes
Antibodies
What is innate immunity?
The immunity that you are born with ( non-specific defence)
Early stage of the immune response. - WBCs
What are the 3 white blood cells involved in innate immunity (non specific defence)?
- Neutrophils
- Macrophages
- Natural Killer (NK) cells
Function of neutrophils in innate immunity? (non-specific body defence)
- Most abundant white blood cells (70%)
- Important in fighting early phases of
bacterial infections - Engulf and destroy microbes at infected sites
Functions of macrophages in innate immunity? (non-specific body defence)
- Major cell type in phagocytosis
- Important in long lasting infections
- Inactive monocytes –> large tissues
- Pseudopodia, migration and phagocytosis
- Largest phagocytes - long lived
- Clean up dead WBC, foreign material, cancer
cells and tissue debris
Functions of natural killer cells in innate immunity? (non-specific body defence)
- Not as differentiated
- Involved in killing virus infected cells,
transplanted bone marrow cells and
malignant tumour cells - Attack cells with surface membrane change
- Pore insertion (perforin)
- Cell lysis
What is adaptive immunity?
Specific immunity - most specialised of the immune system
What cells are involved in adaptive immunity? (specific body defence)
- Lymphocytes
- Antibodies
–> B cells - antibody mediated immunity
–> T cells - cell mediated immunity
When does the adaptive immune system develop?
- Develops shortly after birth and during first
months - First phase (activation) and Effector phase
(memory and elimination) - Defence responses = Specific and targeted
against particular pathogen - More efficient with repeated attacks -
Memory
What is the function of cytotoxic T cells?
Kill virus-infected and damaged cells
What is the function of helper T cells?
Help cytotoxic T cells and B cells in their immune functions
What is the function of B cells?
Produce antibodies
What are the two types of antibody - dependent defences?
- Antigens
- Antigen receptors
What are antigens?
All molecules and structures that can trigger a specific immune reaction
What are antigen receptors?
- Coded for by a small number of genes
- Genetic recombination allows millions of
different receptors to be coded for
Where and when do antigen receptors occur?
- Occurs in bone marrow where unspecialised
cells differentiate into B lymphocytes or T
lymphocytes - Occurs before exposure to antigen
- Around 100,000 receptors per cell, specific to
one antigen
How do antibodies work?
Antibodies bind to antigens and elicit a response to eradicate it.
What is the process of antibody binding?
B cell binds to antigens via membrane antibodies
(assisted by t-helper cell)
Activated lymphocyte
(transforms into memory cell) –>
lies dormant until re-infection
Transforms into plasma cell
Secretion of antibodies into circulation
How many classes of antibodies are there?
5 antibody immunoglobin (Ig) classes
What is IgG? (antibody class)
Most common in blood and lymph
Directly attack microbes and toxins of bacteria and increase phagocytosis
Involved in fighting antigen the second time it appears
Crosses placenta to protect foetus and neonate from infection
72% of antibodies
What is IgA? (antibody class)
Two basic units
Works against bacterial toxins and directly attack some microbes
Most common in Ab in secretions (saliva, bile, colostrum)
8% of antibodies
What is IgM? (antibody class)
Largest antibodies circulating in blood and lymph
First Ab to show up after a microbe infects and activates complement
15% of antibodies
What is IgD? (antibody class)
Acts as surface receptor on B cells together with IgM. Found primarily in blood and lymph
1% of antibodies
What is IgE? (antibody class)
Ab binds to mast cells to facilitate inflammatory response to antigen and cause allergic reactions
4%
What is antibody mediated immunity?
–> Acquired immunity
How can immunity be acquired naturally?
Actively –> infection, contact with pathogen
B cells encounter antigens and
produce antibodies
Passively –> antibodies pass from mother to
foetus via placenta or to infant in
milk
How can immunity be acquired artificially?
Active –> Vaccine, dead or inactive pathogens
Passive–> injection of immune serum
What is self discrimination?
We have our own fingerprint of protein and carbohydrate on cell surfaces - MHC protein complex
B and T cells are exposed to MHC proteins in development so Lymphocytes develop self tolerance for self antigens
What is non-self discrimination?
Failure or loss of self tolerance = autoimmunity
–> production of anti-self antibodies
e.g. autoantibodies against beta cells of pancreas = insulin dependent diabetes mellitus
