Immunology Flashcards
What are pathogens?
disease causing microorganisms that release toxins that kill cells
What is an antigen?
protein molecule that triggers an immune response by lymphocytes
eg pathogen, toxins, abnormal body cells
What blood cells are involved in non specific immunity?
phagocyte
What blood cells are involved in specific immunity?
B-lymphocytes and T-lymphocytes
Describe the process of phagocytosis
phagocyte recognises antigens on pathogen as non self
phagocyte engulfs pathogen
a phagosome forms around the pathogen (vesicle)
a lysosome fuses with the phagosome then releases lysozymes to hydrolyse the pathogen and it is digested
the macrophage presents the pathogens antigens on their surface membrane to become an antigen presenting cell
What is an antigen presenting cell?
cells that display non self antigens on their surface to activate other immune cells
How do T lymphocytes work?
T helper cell receptors bind to non self antigen
divide by mitosis
release cytokines which activates specific b cells and cytotoxic T cells
cytotoxic T cell receptor binds to APC and divide by mitosis
release perofin which kills the apc or pathogen
How do B lymphocytes work?
divide by mitosis when activated
form daughter cells which differentiate into plasma or memory cells
plasma cells produce antibodies
memory cells remain in blood until antigen returns and then they divide rapidly into plasma cells
What is the primary response?
when the antigen first enters the body
slow acting and involves B lymphocytes and T lymphocytes
What is the secondary response?
when the antigen enters the body for a second time, memory cells (specific to one antigen) divide to form plasma cells which produce antibodies
antibodies here are produced faster and in greater quantities
How can someone get ill from the same illness multiple times?
some diseases have a number of different antigens so there is more than one memory cell needed for each antigen
What is active immunity?
when a person is exposed to an antigen and the immune response occurs and they produce their own memory cells
- takes time to develop
- long lasting
What is passive immunity?
antibodies are injected into a person so they do not have their own immune response or make their own memory cells
- fast acting
- short lasting
What is a vaccine?
dead or weakened pathogen or antigen
a form of artificial immunity
How do vaccines work?
specific T lymphocytes detect antigen
release cytokines to activate specific B lymphocytes
B lymphocyte receptor bind to specific antigen
B lymphocytes divide to form clones- plasma /memory
plasma cells produce antibodies
memory cells stay in blood and produce antibodies faster in secondary response
What are monclonal antibodies?
antibodies which are specific to an antigen as they have a specific binding site due to a unique tertiary structure
What is an antibody?
protein with a specific binding site produced by plasma cells that form antigen- antibody complexes
What is the structure of an antibody?
made up of four polypeptide chains
2 heavy chains and 2 light chains
variable region has specific amino acid sequence
the shape / tertiary structure of the binding site is complementary bind with antigens
forms antigen- antibody complex
ELISA test precautions
enzyme linked immunosorbent assay
wash in between to remove unbound antibodies/antigens to avoid false positive
there are control wells; to ensure nothing else is causing the colour change
to ensure the washing steps have been thorough
children receive antibodies from their parents so a positive test could show up
What is the test for an antigen?
apply monoclonal antibody specific to an antigen
wash
apply body fluid suspected of containing antigen
wash
apply monoclonal antibody attached to an enzyme
wash
add substrate- enzyme causes a colour change
What is the test for an antibody eg HIV?
HIV antigen is added
body fluid is added to the well (HIV antibodies will bind to HIV antigen)
wash
monoclonal antibody with enzyme is added (will bind to HIV antigen)
wash
substrate is added and will change colour if HIV antibodies are- if person is HIV positive
Why do antibodies have 2 binding sites?
so they can bind to more than one pathogen which clumps them together (agglutination) which reduces chances of pathogens spreading and attracts phagocytes to engulf lots of pathogen at one time
