[Unit 2.4] Cell recognition and immune system Flashcards
Cells
what defences do humans have against pathogens
skin
mucus
stomach acid
immune system
what is a self cell
a cell of our own body
what is a non-self cell
a cell of a different organism
what must the immune system be able to recognise
pathogens
abnormal cells (cancer/old cells)
toxins
cells from other organisms (same species)
describe the process of phagocytosis
-Phagocyte attracted to pathogen by chemical products. Moves along conc. gradient
-Phagocyte has receptors that bind to chemicals
-Lysosomes migrate to phagosome
-Releases lysozymes that hydrolyse pathogen
-Products are absorbed by phagocyte
-Antigens from pathogen put on membrane
define specific immune responses
slower, specific to each pathogen, longer lasting
define non specific immune responses
immediate, same for all pathogens
examples of specific immune responses
cell mediated response, humoral response
examples of non specific immune responses
physical barrier, phagocytosis
how do cytotoxic T cells work
they bind to infected cell
perforin makes holes in membrane
infected cell lyses
what is the role of cytotoxic T cells
to kill abnormal cells / cells infected
what do helper T cells do
activate B cells
activate cytotoxic T cells
increase rate of phagocytosis
how are T lymphocytes activated
they cannot recognise foreign antigens directly
only respond when presented by antigen presenting cells (phagocytes, macrophage)
how does cell mediated immunity work/ what is the process
-Phagocyte places antigens on membrane
-Antigens fit into immature T cells receptors
-T cells divide rapidly by mitosis and form:
– memory cells
– helper T cells
– cytotoxic T cells
define “humoral”
immune response that involves B cells producing antibodies that circulate in the blood
what is clonal selection
B cells complimentary receptor binds to antigen of pathogen activating it
OR
Helper T cell activates
what is clonal expansion
B cell undergoes mitosis
most turn into plasma cells
some into memory B cells
what do plasma (B) cells do
make antibodies that bind to pathogens antigen
how do long living memory B-cells work
immunological memory
if same pathogen detected again, they divide quicker and create plasma cells.
What is the basic structure of an antibody?
An antibody is composed of four polypeptide chains: two heavy chains and two light chains, forming a Y-shaped molecule.
what is the region of the antibody that binds to the antigen called
variable region/antigen binding site
What role does the constant region of an antibody play?
The constant region determines the class of the antibody and mediates interactions with other immune cells.
What type of bonds contribute to the stability of the antibody structure?
Disulphide bridges
Describe the function/role of antibodies in the immune response.
Antibodies identify and neutralize foreign objects like bacteria and viruses.
do antibodies directly kill pathogens.
no
What is the significance of the hinge region in antibodies?
The hinge region allows flexibility, enabling the antibody to bind effectively to antigens.
what part of the antigen does the variable region bind to
epitope
what makes the variable region unique to each antibody
specific sequence of amino acids
what is it called when the antigen binds to the antigen binding site
antigen-antibody complex
what are the four ways antibodies fight pathogens
agglutination
neutralisation
complement cascade
coat viruses/bacteria
define “agglutination”.
what diseases does it help against
antibodies cause pathogens to stick together. easier for phagocytes to engulf and destroy
most pathogens
define “neutralisation”
what diseases does it help against
neutralises toxins produced by pathogens
bacterial infections
define “complement cascade”
what diseases does it help against
antibodies create holes in bacterium by reacting with blood proteins. cell bursts.
bacterial infections
define “coat viruses / bacteria”
what diseases does it help against
antibodies bind to attachment proteins. prevents virus entering cell. easier for phagocytes to engulf
bacterial or viral diseases
define “monoclonal antibodies”
antibody produced from a single group of genetically identical B cells.
define “direct therapy” in terms of monoclonal antibodies
MA is specific to cancer antigens. they can target and bind to cancer cells. blocking chemical signals that are telling it to rapidly divide
define “indirect therapy” in terms of monoclonal antibodies
cytotoxic drugs binds to MA. MA binds to antigen on targeted cell. Cytotoxic drug destroys the cell.
how are monoclonal antibodies used in diagnosis
antibodies target antigens to measure level of that antigen in the body.
what are the side effects of monoclonal antibodies
vomiting, fever , low blood pressure
what are the ethical issues with monoclonal antibodies
requires animal testing:
immune cells harvested from mice
what does ELISA stand for
enzyme linked immunosorbent assay
define “immunosorbent”
technique of using antibodies absorption property to test for antigens
what are the uses of ELISA
diagnosis
research purposes
detecting proteins, hormones etc (qualitative)
how much antigen present (quantitative)
define “direct ELISA”
using one type of antibody
define “indirect ELISA”
using two different types of antibodies
how does direct ELISA work
add antibody with enzyme added to well
antibodies will bind to antigens
wash unbound antigens with buffered salt solution
add substrate
coloured product will form
what is the purpose of indirect ELISA
to detect small amounts of antigens
increasing sensitivity of colour change
how does indirect ELISA work
antibody complementary to antigen added to well (primary)
antibody with enzyme added to well (secondary)
antibody with enzyme binds to each other and primary antibody. (stack)
unbound antibodies washed with buffered salt solution
add substrate
coloured product will form
what is active specific immunity
making your own antibodies when exposed to antigen
what is passive specific immunity
given someone else’s antibodies
what is natural active specific immunity
antigen enters body naturally. body produces antibodies
what is natural passive specific immunity
antibodies passed from mother to foetus/new-born through placenta/milk
what is artificial active specific immunity
antigens in vaccine introduced to body. antibodies formed
what is artificial passive specific immunity
preformed antibodies injected into body in a serum.
define “herd immunity”
when social circle is vaccinated. even if you’re susceptible, you wont catch disease as there isn’t anyone to give it to you
how do vaccines work
giving someone a weakened or dead pathogen or isolated antigen from pathogen.
difference between active and passive specific immunity
active:
-exposure to antigen
-protection is long term
-takes a while for protection to develop
-memory cells produced
passive:
-no exposure to antigen
-protection is short term
-immediate protection
-no memory cells produed
what are the ethical arguments FOR vaccines
-saves lives
-prevents spreading of disease
-reduces suffering
-cheaper to protect than recover
-herd immunity
what are the ethical arguments AGAINST vaccines
-animal testing
-side effects
-freedom of choice for mandated vaccines
-who gets vaccine first?
-risk to human volunteers at clinical testing
define “antigenic variation”
antigens on virus change due to mutation. new strains of virus emerge
what is the role of reverse transcriptase
replicating the virus. converting RNA to DNA
describe the process of HIV replication
-attachment proteins attach to receptor on helper T cell
-capsid released and uncoats itself. releasing RNA and reverse transcriptase
-reverse transcriptase used to make complementary strand of DNA
-reverse transcriptase turns single stranded DNA into double stranded DNA
-DNA is inserted into host’s genome in nucleus
-host’s enzymes & ribosomes used to make viral proteins
-host’s enzymes make RNA genome copies for new virions
-these infect other helper T cells
what does AIDS stand for
acquired immune deficiency syndrome
what are the symptoms and development of AIDS
initially flu-like symptoms
then latency period (virus is dormant)
low helper T cell count in blood
can take 10 years to develop into AIDS
get sick with diseases most people immune to
infections become more frequent and more life threatening
death is caused by other pathogens or cancer
what determines how long HIV will take to develop into AIDS
strain of HIV, age, genetics
