Transcript the immune system phagocytosis antibody

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
saliva
antibacterial
enzymes
skin
prevents
entry
stomach acid
low pH kills
harmful
microbes
tears
antibacterial
enzymes
mucus linings
traps dirt and
microbes
“good” gut
bacteria out
compete bad
Pathogens
 = disease causing micro-organisms






bacteria
virus
fungi,
protozoa,
parasite,
prion
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
 Monocytes and macrophages
 Provide a non-specific response to
infection
 http://www.microbelibrary.org/imag
es/tterry/anim/phago053.html
Phagocytosis
 Stages in phagocytosis
1. Phagocyte detects chemicals released by a
foreign intruder (e.g. bacteria)
2. Phagocyte moves up the concentration
gradient towards the intruder
3. The phagocyte adheres to the foreign cell
and engulfs it in a vacuole by an infolding of
the cell membrane.
4. Lysosomes (organelles which are rich in
digestive enzymes & found in the
phagocytes cytoplasm) fuse with the
vacuole & release their contents into it.
Phagocytosis
5. 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
An accumulation of :  dead phagocytes
 destroyed bacteria
 dead cells
Lymphocyte
Lymphocytes
Provide a specific immune response to
infectious diseases.
There are 2 types: - T-cells
- B-cells
They produce antibodies.
Antigens
 all cells have
surface markers
called antigens.
 body can recognise
these as self or
non-self (foreign)
Specific response
 Lymphocytes detect presence of foreign
antigens
 Stimulated to produce
specific proteins called
antibodies.
 antibodies combine with their specific
antigen (like a lock and key)
 this renders the pathogen harmless.
 = primary response
Immunity
 = the bodies ability to resist infection
 can be natural or acquired
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
Can you
 Outline the stages in phagocytosis.
 Describe how antibodies work and how
they are specific.
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