Chapter 5 - Cell recognition and the immune system Flashcards
(37 cards)
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