Cell recognition and the immune system Flashcards
What is a pathogen
a bacterium/virus/microorganism that causes disease and triggers immune response
What is the difference between Specific and Non-Specific defence mechanisms
Specific - doesn’t require an adaption and it is an immediate response as your are born with it
Non-Specific - (Phagocytosis) it is learnt and is for only one antigen and takes a longer time
How do lymphocytes recognise self body cells
our cells have identifiable:
- specific molecules on its surface
- specific 3D tertiary structure
- lymphocytes produced in the bone marrow initially only encounter self-antigens
What is a phagocyte
a type of white blood cell that carries out phagocytosis
How do phagocytes defend against pathogens
phagocytosis
- phagocyte follows the chemical trail left behind the pathogen
- the phagocyte engulfs the pathogen to form a phagosome
- lysosomes move towards the pathogen and release lysozymes which hydrolyse the pathogen
- the left over products get absorbed into the cytoplasm of the phagocyte
What is a cell-mediated immunity
cellular response
don’t require antibodies
- pathogens that invade body cells
- phagocytes engulf and hydrolyse the pathogen and present the foreign antigen on its cell surface membrane
- specific T-helper cells bind to the antigen and causing the T-helper cell to rapidly divide by mitosis and form genetically identical clones which can:
- develop into memory cells
- stimulate phagocytosis
- stimulate B-cells to divide and sertete antibodies
- activate cytotoxic T-cells (T-killer cells)
What is hormonal immunity
- suface antigens on the pathogen are taken up by the B-cell
- by endocytosis the B-cell’s presents the antigens on its cell surface membrane
- T-helper cells with complementary receptor bind to these antigens and activate the B-cells go through clonal selection and divide by mitosis to either form:
- plasma cells which secrete specific antibodies for which are complementary to the antigens on the pathogen and destroy it (primary immune response)
- memory B-cells which get stored in the lymph nodes to respond to future infections from the same pathogen (secondary immune response)
How do cytotoxic T-cells kill pathogens
produces a protein called perforin which makes holes in the pathogens membrane making it freely permeable to substances therefore dies
What is an antibody
proteins produced by a B lymphocyte which have a specific binding site, complementary to an antigen
Describe the structure of an antibody
- heavy and light chains make up the protein made up of 4 polypeptide chains
- they have a antigen binding site at one end and a receptor binding site at the other
How do antibodies destroy pathogens
- cause an agglutination of pathogen making it easier for phagocytes to locate them
- serve as a marker to stimulate phagocytes to engulf the pathogen
What is a monoclonal antibody
an antibody produced by a single clone of cells
Explain a use of an monoclonal antibody
can be used to treat cancer by attaching to cancer cells and block the chemical signal the stimulates uncontrollable growth
How does a pregnancy test work
- the placenta produces a protein called hCG which can be detected in the urine
- monoclonal antibodies located in the test strip are linked to colour particles
- if hCG is present the antibodies bind to it to make a hCG-antibody-colour complex that moves down the strip till it is trapped by another type of antibody and the colour is created
What are the reasons FOR and AGAINST the use of monoclonal antibodies
For:
-it has successfully treated many diseases
Against:
- production involves mice that suffer
- testing presents dangers on the user
What’s the difference between PASSIVE and ACTIVE immunity
Passive:
-introducing an individual to an antibody from an outside source
Active:
-stimulating an individual’s immune system to produce antibodies from direct contact with a dead or weakened pathogen
What are 3 features of a successful vaccination program
- must be economically available to immunitise most of the vulnerable population
- few to no side effects of the vaccine to prevent individuals from being discouraged about taking the vaccine
- must be possible to vaccinate the vast majority of the vulnerable population for herd immunity
What is herd immunity
when a large proportion of a population has been vaccinated making it difficult for the pathogen to spread
What are the reasons FOR and AGAINST vaccination programs
For:
- reduces infection
- herd immunity
Against:
- testing involves animals
- possible health risks like allergies
What is HIV
a virus that causes AIDS
What is the structure of HIV
- on the outside is a lipid envelope embedded with attachment proteins
- inside the envelope is a capsid that encloses single RNA strands and enzymes including reverse transcriptase
what is meant by retrovirus
a virus that has the ability to turn RNA into DNA with the use of reverse transcriptase
How does HIV infect CD4
- HIV enters the bloodstream
- it binds to a CD4 proteins located most frequently on T-helper cells
- the protein capsid binds with their cell-surface membrane and the RNA and reverse transcriptase enters the t-helper cells
- the reverse transcriptase turns the HIV RNA into viral DNA which enters the T-helper cells nucleus and DNA
- the HIV DNA in the nucleus creates mRNA which codes for the production of more viral proteins
- the mRNA strands move our the nuclear pores and make more HIV particles by protein synthesis
- HIV particles break away from the T-helper cell
How does HIV lead to AIDS
by HIV killing or interfering with the functions of T-helper cells, this decreases the amount of T-helper cells in the blood, and efficient cell-mediated immunity therefore the individual becomes more vulnerable to disease
