Immune system : Immune system By the end of the lesson you should be able to
Outline the stages in phagocytosis.
Describe how antibodies work and how they are specific.
First lines of defence : First lines of defence skin prevents entry tears antibacterial enzymes saliva antibacterial enzymes stomach acid low pH kills harmful microbes mucus linings traps dirt and microbes “good” gut bacteria out compete bad
Pathogens : Pathogens = disease causing micro-organisms
bacteria
virus
fungi,
protozoa,
parasite,
prion
Second lines of defence : Second lines of defence Involves white blood cells
Non-specific response
invading pathogens are targeted by macrophages
Specific response
lymphocytes produce chemicals called antibodies that target specific pathogens
Phagocytes : Phagocytes
Phagocytes : Phagocytes Monocytes and macrophages
Provide a non-specific response to infection
http://www.microbelibrary.org/images/tterry/anim/phago053.html
Phagocytosis : Phagocytosis Stages in phagocytosis
Phagocyte detects chemicals released by a foreign intruder (e.g. bacteria)
Phagocyte moves up the concentration gradient towards the intruder
The phagocyte adheres to the foreign cell and engulfs it in a vacuole by an infolding of the cell membrane.
Lysosomes (organelles which are rich in digestive enzymes & found in the phagocytes cytoplasm) fuse with the vacuole & release their contents into it.
Phagocytosis : Phagocytosis The bacterium is digested by the enzymes, and the breakdown products are absorbed by the phagocyte.
During infection, hundreds of phagocytes are needed.
Pus is dead bacteria and phagocytes!
link to phagocytosis
Pus : Pus An accumulation of : -
dead phagocytes
destroyed bacteria
dead cells
Lymphocyte : Lymphocyte
Lymphocytes : Lymphocytes Provide a specific immune response to
infectious diseases.
There are 2 types: -
- T-cells - B-cells
They produce antibodies.
Antigens : Antigens all cells have surface markers called antigens.
body can recognise these as self or non-self (foreign)
Specific response : Specific response Lymphocytes detect presence of foreign antigens
Stimulated to produce
specific proteins called
antibodies.
Slide14 : antibodies combine with their specific antigen (like a lock and key)
this renders the pathogen harmless.
= primary response
Immunity : Immunity = the bodies ability to resist infection
can be natural or acquired
Immunological memory : Immunological memory after an infection is fought off some lymphocytes become memory cells.
if same pathogen returns memory cells stimulate the produce the specific antibody very rapidly.
the infection is fought off before symptoms appear = secondary response
vaccines can stimulate same response
Immune system : Immune system Can you
Outline the stages in phagocytosis.
Describe how antibodies work and how they are specific.