2c (immune system) Flashcards
cells and the immune system
What is an antigen?
A molecule (protein) found on the surface of cells that can generate an immune response when detected by the body.
4 examples of antigen presenting cells
phagocyte that engulfed a pathogen, body cell invaded by a virus, cancerous cell, foreign transplanted material
What is a pathogen?
A microrganism that causes disease
What are the four main stages of the immune response?
Phagocytes engulf pathogens
phagocytes activate T cells
T cells activate B cells which divide into plasma cells
Plasma cells make more antibodies to a specific antigen
What is the first cell in the immune system to respond to antigens?
Phagocytes
Describe phagocytosis
Phagocyte recognises foreign antigen
Cytoplasm of phagocyte moves round pathogen engulfing it
Pathogen is now contained in phagocytic vacuole in the cytoplasm of the phagocyte
A lysosome fuses with the phagocytic vacuole and lysozymes digest pathogen
Phagocyte present pathogens antigens by sticking them on its surface to activate other immune system cells
What is a T cell/ T lymphocyte? where are they produced/ matured?
Type of white blood cell with receptor proteins on surface which bind to complimentary antigens presented to it by phagocytes which activate it
produced in bone marrow and matured in thalamus gland
cell mediated response
What is a T helper cell
T cell that releases chemical signals (cytokines) that activate and stimulate phagocytes and cytotoxic T cells. Also activate B cells which secrete antibodies
What is a cytotoxic T cell?
what happens when theyre activated?
T cell that kills abnormal and foreign cells
once activated, proliferate to make clones specific to 1 antigen, some differentiate into long lived memory t cells
most mature to attack and destroy infected cells
how do cytotoxic t cells destroy cells?
secrete perforin which forms pore in membrane of target cell
secret granzyme which enters cell through pores and activates enzymes in cell to cause cell death
pores also mean contents of cell leaks out causing death
What is the role of B cells? where are they produced/ matured?
Antibody on its surface binds to complimentary antigen
This and substances released from helper T cells activated B cells (clonal selection)
Activated B cell divides into plasma cells
produced in bone marrow and matured in lymph nodes
humoral response
What are plasma cells?
Clones of B cells that secrete antibodies specific to antigen
Monoclonal antibodies
Bind to antigens on surface of pathogen
Structure of antibodies
Proteins
Specificity of antibody depends on variable regions which form antigen binding sites
Variable region with unique tertiary structure complimentary to specific antigen
Same constant region
2 light 2 heavy???
function of antibodies
coat pathogen so easier for phagocytes to engulf
coat pathogen to prevent entering host
bind to and neutralise toxins produced by pathogens
What is agglutination?
antibodies have 2 binding sites so can bind to 2 antigens at a time. results in the clumping together of cells or particles which assists phagocytosis
What is cellular immune response?
T cells and other immune system cells they interact with
Eg phagocytes
What is humoral response?
B cells, clonal selection and production of monoclonal antibodies from the humoral response
What is a primary immune response?
Antigen first activates immune system
Slow as not many b cells to make antibodies
Eventually enough antibody made to overcome infection but person shows symptoms
T and b cells produce memory cells which stay in body. Memory t recognise specific antigen and memory b record specific antibodies needed
Person now immune
What does it mean to be immune?
have memory B cells which can divide and differentiate into plasma cells and quickly destroy pathogens before you get symptoms
What is the secondary immune response
Same pathogen enters second time and immune system can produce quicker stronger immune response
Clonal selection happens quicker
Memory b cells activated and divide into plasma cells that produce antibodies
Memory t cells activated and divide into correct T cell to kill cell carrying antigen
Gets rid of pathogen before show symptoms (immune)
what is a vaccine?
what does it contain?
dead or inactive part of a pathogen that stimulates an immune response
contains antigens that cause body to produce memory cells wo causing disease so immune wo symptoms
what is herd immunity?
more people with vaccine means less people with disease.
vaccinated people mean it is hard to spread even to those not vaccinated so helps people who cant get vaccine