immune system 3.2.4 Flashcards
what is an antigen
any part of an organism or substance that is recognised as non self by the immune system and stimulates an immune response
4 examples that act as antigens
pathogens
non self material
cancerous cell antigens
toxins
phagocytosis
1 phagocyte attracted to chemicals produced by pathogen
2 recognises pathogen antigens and binds
3 engulfs pathogen forming phagosome
4 lysosomes fuse with phagosome
5 lysozymes hydrolyse pathogen
6 phagocyte presents pathogens antigens to activate other immune cells
cellular response (T cells)
1 pathogen attacks body cell
2 infected phagocyte cell presents antigens
3 helper T cell with complementary shaped receptors binds to the antigens
4 helper T cell activated to divide by mitosis producing clones
what can T cell clones differentiate to do
memory cells
stimulate phagocytosis
stimulate B cells
activate cytotoxic T cells
what do cytotoxic T cells do
kill infected cells by forming pores in the membrane
using a protein called perforin
humoral response (b cells)
1 b cell binds to complementary antigen
2 b cell ingests processes and presents antigens
3 helper t cell with complementary receptors attaches to presented antigens on b cell
4 b cell is stimulated to divide via mitosis, forming clones
5 clones differentiate into memory cells and plasma cells
6 plasma cells release/produce antibodies (against specific pathogen)
what is another word for b cell ingesting
endocytosis
what is clonal selection
when specific antigens select specific b cells that are complementary and stimulate them to form clones
define antibody
protein produced by the immune system in response to a specific antigen
list parts/structure of antibody
light chain
heavy chain
variable region
constant region
disulphide bridge
antigen binding site
what is agglutination
clumping together of bacterial cells so phagocytes can easily engulf them in a group
define active immunity
results from immune system producing memory cells following exposure to an antigen
define passive immunity
results from being given antibodies from a different organism
define herd immunity
where unvaccinated people are protected because occurrence of a disease is reduced by number of people who are vaccinated.
4 differences between active and passive immunity
1 active involves memory cells, passive does not
2 active involves production of antibodies by plasma cells
3 passive is short term because antibody is broken down, active is long term because antibodies produced in response to antigen
4 active takes time to develop, passive is fast acting
how to vaccines work
1 vaccine contains antigens from pathogen
2 macrophage presents antigens on surface of cell
3 t cell with complementary receptor proteins binds to antigen
4 t cell stimulates b cells with complementary antibodies to divide by mitosis and form clones
5 plasma cells secrete antibodies specific to the pathogens antigens
6 b cell secretes large amounts of antibody
define monoclonal antibody
a single desired type of antibody
B cell isolated and cloned
all have same tertiary structure
what do monoclonal antibodies used to do
target specific cells and substances, diagnose disease and in pregnancy testing.
how does indirect monoclonal antibody therapy work
cytotoxic/radioactive drug attached to monoclonal antibody. when MA attaches to the target cell it kills the cell.
how does pregnancy testing work
MA bind to HCG hormone tiny amounts of the hormone are passed out of the body in urine and this is picked up by the MAs.
3 ethical issues of monoclonal antibodies
- involves deliberately inducing cancer in mice
- have been some deaths associated with MA use
- drug trials of new drugs using MAs has caused harm in the past
what does the eliza test do
enables you to see if a patient has a particular antibody to a certain antigen.
how does the eliza test work
1 antigen is adsorbed to well
2 patient serum is added, complimentary antibody binds to antigen (wash out)
3 enzyme linked antiHISG is added and binds to bound antibody (wash out)
4 enzyme substrate is added and reaction produces a product that causes a visible colour change
list the structure/parts of a HIV virus
genetic material RNA
attachment protein
capsid
lipid envelope
matrix
reverse transcriptase enzyme
how does HIV cause the symptoms of AIDs
1 kills/interferes with normal functioning of helper t cells
2 body cannot produce adequate numbers of b cells to produce antibodies or Tc cells to kill infected cells
3 immune response is reduced and is more susceptible to infections and cancer
describe how HIV is replicated (5 marks)
attatchment proteins attach to receptors on helper T cell
RNA enters cell
reverse transcriptase converts RNA to DNA
viral proteins produced
virus assembled and released from cell
how is HIV replicated once INSIDE helper T cell (4 marks)
RNA converted into DNA using reverse transcriptase
DNA inserted
DNA transcribed into RNA
RNA translated into viral proteins
Describe how a phagocyte destroys a pathogen present in the blood (3 marks)
engulfs
forms phagosome and fuses with lysosome
lysozymes hydrolyse
