Immunology Flashcards
how does the immune system distungiush cells between “self” and “non-self”
antigens
what is the definition of an antigen
a foreign molecule, usually a protein, that stimuluates an immune response
True or False
Antigens have a specific shape and tertiry structure that is complementary to an anitbody
True
what is the non-specific immunity response
phagocytes
explain the process of phagocytosis
- phagocytes move to the site of infection and engulf the pathogen. This forms a vesicle known as a phagosome
- phagocytes contain many lyosomes which fuse with the phagosome
- the hydrolytic enzymes called lysozymes in the lyosome hydrolyse the pathogen
explain the process of antigen presentation
- after phagocytosis they display part of the pathogen on its cell surface membrane
- this allows activation of other immune cells such as T and B cells
what is the specific immune reponse
involves immune cells becoming activated in response to presence of a specific antigen of a pathogen
what does antigen presentation initiate
the cellular response
T helper cells
explain the first process of the cellular response
- they have a receptor that has a complementary shape to the specific antigen
- upon binding to the antigen, the T helper becomes activated and divides by mitosis
the activated T helper cells release ——-
cytokines
explain what cytokines do
- stimulate B cells to divide by mitosis
- stimulate phagocytes
- stimulates cytotoxic T cells
explain the role of cytotoxic cells
- contain receptors which bind to antigens on the surface of either virally infected or cancerous cells
- the cytotoxic cells then release perforin which makes holes in the cell surface membrane of the cell
- this leads to the cell undergoing apoptosis (cell death) and being destroyed
involves antibodies
explain the humoral response
- B cells are stimulated directly by the antigen binding to the receptors
- or stimulayed indirectly by the release of cytokines
- upon stimulation, the B cells divide by mitosis to produce clones
- some of these B cells differentiate into plasma cells which produce and release large quantities of monoclonal antibodies. This is the primary response
- some B cells become memory cells. This is the secondary response
explain the structure of an antibody
- quaternary protein where 4 polypeptide chains are joined together by disulphide bridges
what happens when an antibody binds to its antigen
an antigen-antibody complex is formed
what is agglutination
- antibodies bind to antigens
- they clump them together
- this marks the antigens and helps attract phagocytes
what do vaccines contain
- dead or weakened form of the pathogen
- specific antigen
explain how vaccines make use of the primary and secondary response
- the stimulation of B cells will lead to the differentiation into plasma cells and the production of antibodies -primary response
- memory cells are also produced - secondary response
explain herd immunity
- vaccinated individuals recover from an infection quickly
- therefore less likely to spread the pathogen to unvaccinated individuals
explain the steps of ELISA test
- monoclonal antibodies are fixed to the bottom of the test well
- a sample, potentially containing the antigen, is added to the well and will bind to the antigen-binding site on the antibody
- the well is washed with water
- a second monoclonal antibody is now added - which is attached to an enzyme - and will bind to another part of the antigen if present
- the well is washed again
- a substrate is added and the enzymes on the second monoclonal antibody will convert this to a different colour
- the colour change is a positive result
give 4 key features of HIV
- RNA genome
- contains reverse transcriptase
- genome is surrounded by a protein coat called capsid
- the lipid envelope contains attachment proteins
explain the replication of HIV
- attachment proteins on HIV bind to specific receptors on T helper cells
- viral RNA and reverse transcriptase enter the cell
- the reverse transcriptase converts viral RNA into DNA
- the viral DNA moves into the nucleus and is inserted into the host cell genome
- transcription of HIV DNA into HIV mRNA which is translated to produce HIV proteins
- the infected T helper cells starts to assemble new virus particles
- virus particles are released from the T helper cell
how do antibiotics work
- they prevent bacteria from synthesising murein cell wall
- directly damage the cell wall
