Module 4 : Section 1 - The Immune System Flashcards
What triggers an immune response
Foreign antigens
What are antigens
Molecules (usually proteins or polysaccharide) found in the surface of cells
What happens when a pathogen (e.g. bacterium) invades the body
The antigens in its cell surface are identified as foreign so this activated the cells in the immune system
What two stages are involved in the immune response
- specific
- non-specific
What is the specific and non specific responses
- non specific happens in the same way for all microorganisms no matter what antigens they have
- specific response is antigen-specific which involves white blood cells and T and B lymphocytes
What are the four main stages in the immune response
- phagocytes engulf pathogens
- phagocytes activate T lymphocytes
- T lymphocytes activate B lymphocytes which divide to plasma cells
- plasma cells make more antibodies to a specific antigen
What is a phagocyte
- A white blood cell that carries out phagocytosis
- they are found in blood and tissues, they carry out a non specific immune response
How do phagocytes work
- it recognises the antigens on a pathogen
- phagocytes cytoplasm moves round the pathogen (engulfing it) presence of opsonins make it easier when engulfing
- the pathogen now contained in a phagosome in the cytoplasm of a phagocyte
- a lysosome fuses with the phagosome, the enzymes in the Lysosome break down the pathogen
- phagocyte then present the pathogens antigens on its surface to activate other immune system cells. It acts as an antigen presenting cell
What are neutrophils
- first type of white blood cell to respond to a pathogen
- they move towards a wound in response to signals from cytokines which get released by cells at the site of the wound
What are opsonins
Molecules in the blood that attach to foreign antigens to aid phagocytosis
what does cell communication consist of (phagocytes activating t lymphocytes)
- presentation
- clonal selection
- clonal expansion
- differentiation
what is the presentation stage of cell communication
the antigens are presented by an antigen presenting cell
what is clonal selection
- when the receptor of a t lymphocytes meets a complementary antigen it binds to it
- each lymphocyte will bind to a different antigen
- this activates the t lymphocyte
what is clonal expansion
when the chosen t lymphocyte divides to produce clones of itself
what is differentiation
the process in which the t lymphocytes become either t helper, killer or regulatory cells or memory cells
what do t helper cells do
these release substances to activate B lymphocytes and T killer cells
what do t killer cells do
these attach to and kill cells that are infected with the virus
what do t regulatory cells do
these suppress the immune response from other WBC’s. this helps stop immune system cells from mistakenly attacking the host’s body cell
what are b lymphocytes
- type of white blood cell
- covered with proteins called antibodies
- each b lymphocyte has a different shaped antibody on its surface, meaning each of them will bind to a different antigen
what do antibodies do
bind to antigens to form an antibody-antigen complex
when a b lymphocyte is selected what happens
it divides by mitosis into plasma cells and memory cells
What are plasma cells
- Clones of the b lymphocyte (identical to the selected b lymphocyte)
- they secrete loads of the antibody which is specific to the antigen into the blood
What is the variable region of an antibody
- forms the antigen binding site and the shape of this is complementary to a particular antigen
- found in the tips of the antibody
- differs between antibodies
What is the hinge region of an antibody
Allows flexibility when the antibody binds to the antigen
