Body Defence 1 Flashcards by Angharad Jones

How does the the body deal with threats?

Protects from pathogens
Detects antigens

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Where are pathogens found?

Found in air, food and water and micro-organisms that cause disease

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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)

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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

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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

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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

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What are the 2 primary lymphoid organs?

The bone marrow
The thymus

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What are the 3 secondary lymphoid organs?

Tonsils
Lymph nodes
the Spleen

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What are the interior defence organs of immunological protection?

Tonsils and adenoids
Lymph nodes
Lymphatic vessels
Thymus
Spleen
Peyer’s patches
Appendix
Bone marrow

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What does the lymphatic system do?

Circulates a clear fluid, lymph, it travels towards the heart in open circulatory system.

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What is lymph?

Lymph is filtered interstitial fluid

(filtered from plasma)

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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

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How can lymph fight infection?

Lymph transports white blood cells to fight infection

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What happens when lymph passes through lymph nodes?

The lymph nodes contain lymphocytes where microbes and wastes are filtered out

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What are the 3 non-specific exterior first line of defences?

Skin
Mucous membrane
Secretions

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What are the 3 non-specific interior second line of defences?

Phagocytic white blood cells
Antimicrobial proteins
Inflammatory response

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What are the 2 specific third line of defences?

Lymphocytes
Antibodies

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What is innate immunity?

The immunity that you are born with ( non-specific defence)

Early stage of the immune response. - WBCs

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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