Cells-Immunity Flashcards
What is a pathogen?
a disease causing micro-organism
e.g. bacteria, virus, fungi
Body’s defence against pathogens?
Barriers (prevents pathogens entering the body)
Phagocytes (perform phagocytosis and stimulate specific response)
Specific Response/ cell mediat (uses lymphocytes to produce memory cells and antibodies)
What are the Barriers (I)?
Skin
Cilia & Mucus in Lungs
Stomach Acid
Lysozymes in tears
Describe the process of Phagocytosis ?
pathogen releases chemicals
this attracts the phagocyte
the phagocyte binds to the pathogen
the phagocyte engulfs the pathogen
forms a phagosome around the pathogen
lysosomes inside the phagocyte release digestive enzymes into the phagosome
breaking down the pathogen by hydrolysis
Describe the Specific Response (III)?
phagocytes perform phagocytosis (engulf and destroy pathogen) without destroying the antigen, they place antigens on their surface, they present antigens
t lymphocytes (t cells) bind to the antigen and become stimulated
they divide by mitosis to form 3 types of cells: t helper, t killer, t memory
t helper cells stimulate b lymphocytes (b cells)
t killer cells kill infected cells (infected by virus)
t memory cells provide long term immunity
b lymphocytes (b cells) engulf and present antigens on their surface, the t helper cells bind to this
the b cells become stimulated and divide by mitosis to make 2 types of cells: Plasma
Cells & B Memory Cells
Plasma cells make antibodies
B memory cells provide long term immunity
What is an antigen?
a protein on the surface of a pathogen that stimulates an immune response
How does the immune response lead to production of antibodies?
the phagocytes stimulate the t cells, the t cells form t helper cells, the t helper cells stimulate the b cells, the b cells form plasma cells, the plasma cells make antibodies
What is an antibody?
protein
made by plasma cells
has 3 regions: variable region, hinge region, constant region
variable region has a different shape in each antibody, contains the antigen binding sites, these bind to
complementary antigens (on a pathogen) to form an antigen-antibody complex, destroying the pathogen
hinge region gives the antibody flexibility
constant region the same shape in all antibodies, binds to phagocytes to help with phagocytosis
How do Memory cells (B/T) work?
made during the specific immune response after a new infection by a pathogen (called a primary infection)
B and T memory cells remain in the blood
if person is reinfected by the same pathogen (called a secondary infection) the memory cells will recognise
the pathogen and produce antibodies RAPIDLY and to a LARGE amount
therefore the pathogen is killed before it can cause harm = immunity
How does a vaccine produce immunity?
involves giving an injection that contains dead/weakened pathogens that
carry antigens which stimulates the immune response leading to production of antibodies & memory cells
Active immunity
individual has memory cells – can make their own antibodies & provides long term immunity
Passive immunity?
person given antibodies, these work then die, no long term immunity, no memory cells.
How does active immunity occur?
naturally = by primary infection, artificially = by vaccination
How does passive immunity occur?
naturally = from mother to baby (placenta or breast milk), artificially = by injection
Successful Vaccination Programme?
produce suitable vaccine (effective – make memory cells, does not cause disease, no major side effects,low cost,easily produced/transported/stored/administered)
herd immunity
