Transcript immune systemgd

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 by
shedding causing
acidic conditions
sweat food from sweat
allows good bacteria to live,
these repel pathogenic
bacteria
stomach acid
low pH kills
harmful
microbes
tears
antibacterial
enzymes
Nose mucus
linings traps dirt
and microbes
“good” large
intestine bacteria
keep out pathogens
by competing with
bad
Pathogens
 = disease causing micro-organisms





bacteria
virus
fungi,
protozoa,
parasite,
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
 These are a general name for
Monocytes and macrophages
 Provide a non-specific response to
infection
Phagocytosis
 Stages in phagocytosis
1. Phagocyte detects chemicals released by a
foreign intruder (e.g. bacteria)
2. The phagocyte adheres to the foreign cell
and engulfs it in a vacuole by an infolding of
the cell membrane.
3. Lysosomes ( 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!
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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