B6.3 Part 2 Flashcards
Main barrier to infections of animals
= skin
If skin cut/grazed, pathogens enter body
How does the skin stop microorganisms (pathogens) entering body
- seal cut as quickly as possible, forming a SCAB
- stops you losing too much blood
- platelets essential for helping blood clot (small fragments from cells made in bone marrow)
How do scabs form
- skin cut & starts to bleed, blood leaks out of body
- platelets change blood protein fibrinogen into fibrin, forms network of fibres in cut
- red blood cells trapped in fibres, forms blood clot
- clot hardens to form scab, keeps skin clean & gives it time to heal
- scab falls off
Defence mechanisms in the human body
- skin: outer cells difficult to penetrate, sweat glands produce oils to kill microorganisms
- acid on stomach: kill pathogens present in contaminated food/drink
- cilia & mucus in airways: mucus traps microorganism, cilia sweep mucus to back of throat where its swallowed, sent to stomach
- nasal hairs: keep out dust & large microorganisms
- tears: contain enzymes (lysozyme) that kill bacteria
Type of white blood cells:
- Phagocytes: engulf (ingest) microorganisms, make enzymes that digest microorganisms
- Lymphocytes: make antitoxins / antibodies
What part of the body prevents pathogens that have entered the body causing disease
= immune system
- main form of defence = white blood cells
Antibodies
- proteins that bind to antigens on surface of microorganisms
- pathogen ingested by phagocyte cell & destroyed
- each antibody binds to only 1 type of antigen, so only 1 type of microorganism
- new microorganism enters body = different lymphocyte makes new antibody to fight it
Immunity
Ability of the body to fight off a microorganism before it has the ability to cause disease
- antibodies destroy pathogens before they cause illness
Why does immunity occur in the body
- after disease successfully removed from body
- white blood cells can make same antibodies more quickly if infection occurs again
= immunity to disease
Monoclonal Antibodies
- produced in laboratory using hybridoma cells = fusion of cancer cells (myeloma) and lymphocytes
- monoclonal = produced by single clone of cells
- designed to target specific type of cell
- bind to antigens of target cell, kills cell, prevents it operating effectively
How are monoclonal antibodies produced
- genetically modified mice injected with required antigen
- body produces immune response, producing specific antibodies
- anti-body producing lymphocyte cells collected
- cant survive outside body so fused with myeloma (cancerous) cells from bone marrow (reproduce indefinitely)
- fused cell = hybridoma
- as hybridoma cells reproduce, form clones
- each clone produces required antibodies, are harvested
- these proteins = monoclonal antibodies
How are monoclonal antibodies used in pregnancy testing
- bind to hCG hormone protein (produced during pregnancy), causing colour change reaction
- so used on home pregnancy tests
How are monoclonal antibodies used for detecting disease
- act as markers, bind to specific antigen, confirm its presence
Eg. Antigens of prostate cancer cells in men = early diagnosis for cancer
How are monoclonal antibodies used for treating cancers
- carry drugs / radioactive substances directly to cancer cell, increasing effectiveness of treatment & minimises damage to surrounding tissue
- breast cancer
- stomach cancer
- bowel cancer
How do vaccines work
- small amounts of dead / inactive pathogen put into body (injection)
- antigens in vaccine stimulate white blood cells (lymphocytes) to make antibodies to the pathogen
- antibodies destroy antigens without risk of person getting disease
- person immune to future infections by pathogen
(as body can respond rapidly & make correct antibody as if person already had disease)
