Chapter 5 - Cell recognition and the immune system Flashcards
two lymphocyte responses?
- cell-mediated (T-lymphocytes)
- humoural responses (B-lymphocytes)
definition of a pathogen?
any foreign body/microorganism that causes disease
how are pathogens identified as non self?
specific molecules on cell surface membrane
what molecules would be identified by the body? (4)
- pathogens e.g. viruses
- cells from other organisms
- toxins
- abnormal body cells e.g. cancers
how do lymphocytes recognise own cells in adults? (3)
- lymphocytes produced in bone marrow only encounter self antigens
- any lymphocytes which show an immune response towards self-antigens undergo apoptocis
- no clones of anti-self lymphocytes appear in blood
how do lymphocytes recognise own cells in a fetus?(1)
- anti self lymphocytes die or are suppressed
outline phagocytosis (5)
- Phagocyte attracted to pathogen by chemical products along concentration gradient
- phagocyte receptors bind to antigens on surface of pathogen
- lysosomes in phagocyte migrate to the phagosome which is forming
- lysosomes release lysozymes into phagosome, which hydrolyses the pathogen
- products of hydrolysis are absorbed by phagocyte
definition of an antigen
part of an organism/substance that is recognised as non-self by the body to trigger an immune response e.g. cell surface proteins on a pathogen
what are the two types of lymphocyte?
B lymphocytes
T lymphocytes
where do the two main types of lymphocyte form/mature?
B - in the bone marrow (humoural immunity)
T - in the thymus gland (cell mediated immunity)
How are T-lymphocytes able to recognise invading cells? (4)
- phagocyte present antigens of engulfed pathogens on their surface
- or cells invaded by a virus present antigens on their surface
- transplanted cells have different antigens
- cancer cells have different antigens
Why is it that T-lymphocytes are said to be involved in cell-mediated immunity?
they only respond to antigens presented on cells rather than in fluids
outline the response of a T-lymphocyte to the detection of a pathogen (4)
- phagocyte engulfs pathogen and presents antigens on its surface
- receptors on specific T helper cells fit exactly onto these antigens
- attachment prompts T cell to divide rapidly by mitosis
- these daughter cells; stimulate phagocytes to carry out phagocytosis, stimulate B-cells to divide and produce antibodies - develop into memory cells, activate cytotoxic T cells.
How do cytotoxic T cells kill infected cells? (3)
- produce protein called perforin
- this makes many holes in the CSM
- cell becomes freely permeable to everything and dies
What are antibodies?
specific protein produced by B cells in response to the presence of the appropriate antigen
outline the process of humoural immunity by B-lymphocytes (4)
- B-cell with complimentary antibody attaches to antigen
- antigen enters by endocytosis and is presented on cell surface
- T helper cells bind to processed antigens triggering B cells to divide by mitosis
- all clones produce same antibody therefore known as monoclonal (variety of monoclonal antibodies used to fight one type of pathogen due to antigenic variability)
what do the cells of B cell clones develop into? (2)
plasma cells - secrete antibodies directly into blood plasma
memory cells - responsible for secondary immune response, able to divide rapidly
how do antibodies assist in the destruction of pathogens? (2)
- cause agglutination, clumps them together making it easier for phagocytes to engulf
- mark pathogens of phagocytes to engulf
What are monoclonal antibodies?
- specific to one antigen
- produced by a single clone
outline how monoclonal antibody therapy can be used to treat cancer (3)
- monoclonal antibodies produced specific to antigens of cancer cells
- antibodies given to patient to attach to cancer
- stop chemical signals that stimulate uncontrolled growth and replication of cancer
why might monoclonal antibody therapy be a better treatment than other cancer treatments e.g. chemo?
- specific to patient
- less side effects, own antibodies
give 2 examples of diseases that can be diagnosed using antibody testing
influenza
hepititus
chlamydia
prostate cancer
how is early pregnancy detected?
- hormone HCG released from placenta in urine
- binds to antibody-colour complex causing a colour change
state 3 ethical issues for the use of monoclonal antibodies
- production uses mice who have cancer deliberately induced
- patients must have informed consent
- drugs trials are not always safe
what is passive immunity? (2)
- introduction of antibodies from outside e.g. antivenom
- not long lasting
what is active immunity? (2)
- stimulation of antibody production from own immune system
- natural active immunity, artificial active immunity
what is natural active immunity?
when an individual is naturally infected with a disease which stimulates an immune response which leaves memory cells
what is artificial active immunity?
vaccination - purposeful introduction of disease causing an immune response and memory cells
what is vaccination?
introduction of appropriate disease (or/including antigens) into body to induce artificial immunity
what do vaccines aim to produce on the body?
immunity to secondary exposure through memory cells
state the features of a successful vaccination programme (5)
- economically viable on a large scale
- few side effects so people aren’t discouraged
- means of production, storage, transport
- proper administering equipment e.g. needles
- possible to vaccinate majority for herd immunity
what are the reasons a vaccination might not lead to a disease being eliminated? (6)
- not all become immune, faulty immune systems
- may develop disease just after vaccination but before immunity
- pathogen may frequently mutate (antigenic variability)
- too many strains of pathogen to vaccinate against them all
- pathogens may hide from immune system
- people may object to vaccination programs
ethics of vaccination? (7)
- production , animals
- side effects, long term harm
- informed consent in human testing not totally possible
- use of countries in which disease is widespread to trial vaccine
- compulsory vaccination
- expensive vaccination for almost eradicated diseases
- individual health risks vs population health
how does HIV replicate? (6)
- HIV binds to CD4 on (usually) T helper cells
- capsid fuses to CSM, RNA and enzymes enter T helper cell
- HIV reverse transcriptase makes HIV DNA
- DNA inserted into T helper cell nucleus
- nucleus the makes mRNA as if it were the cells own DNA
- HIV breaks way with part of CSM forming its lipid envelope
How does HIV cause symptoms of AIDS? (3)
- killing/interferring with normal functions of T helper cells
- T helper cells not available for cell mediated immunity
- means no B cells produced of cytotoxic T cells, means the body can’t respond to any infection
technique for ELISA test? (7)
- apply sample to surface and allow binding
- wash away unattached antigens
- add specific antibody
- wash away excess antibody after time for binding
- add second antibody that binds to first one
- add colourless substrate of enzyme
- amount of antigen present is relative to the intensity of colour which develops
Why do viruses not respond to antibiotics? (2)
- rely on host cells for metabolic activities (antibiotics usually work by disrupting metabolic activities)
- protein coat rather than murien cell wall means antibiotics can’t break down
