Disease and Immunity Flashcards
Define a pathogen
A microorganism that causes disease
What is an antigen?
A protein that stimulates an immune response/ production of antibodies
What can antigens identify?
Pathogens
Cells from other organisms of the same species
Abnormal cells
Toxins
Define the non-specific immune response
Present since birth
Effective against a wide range of pathogens
What is an example of a non-specific immune response?
Phagocytosis
Describe phagocytosis
Phagocyte recognises and binds to protein antigen on pathogen
Engulfs pathogen
Encloses it in a vesicle
The vesicle fuses with lysosomes
Lysosomes contain lysozyme
Hydrolytic enzymes digest the pathogen, by hydrolysis of the molecule
Phagocyte places antigen from the pathogen on its surface to become an antigen-presenting cell
What is an APC?
Cells infected with a virus
A phagocyte that has engulfed a pathogen
An abnormal cell such as a cancer cell
Describe the cellular response
Receptors on specific T helper cell binds to the antigen on the APC
This stimulates the T helper cells to divide by mitosis to produce genetically identical clones that are able to differentiate into cytotoxic T cells, memory cells, T helper cells
T helper cells release cytokines that activate B cells and cytotoxic T cells
Cytotoxic T cells destroy infected body cells by binding onto antigens and by releasing perforin which creates holes in the cell membrane of infected and abnormal cells
Describe the humoral response
Specific B cells have specific receptors complementary to the antigens on the invading pathogens
Once they bind to the antigen and are activated by the t helper cell, they can divide by mitosis to produce identical clones (clonal selection)
These clones can differentiate into plasma cells or memory cells
Plasma cells can secrete antibodies that are complementary to the shape of the antigen
These bind to the antigen to form antigen-antibody complex
What is the primary response?
The humoral response
B cells are activated to differentiate into plasma cells to secrete antibodies
What is the secondary response
The memory B cells can differentiate into plasma cells to secrete antibodies
That are complementary to the shape of the antigen on the pathogen of reinfection
Long term immunity is achieved
What are the differences between the cellular and humoral responses?
Cellular:
T cells
No antibodies produced
Act on damaged/infected cells
Humoral:
B cells
Antibodies produced
Act on invading pathogens
What are the similarities between the cellular and humoral responses?
They both produce memory cells
