2.4 Immunity Flashcards
what is a specific response
slower and specific to each pathogen
what is a non specific response
response is same for every pathogen
examples of non specific responses
phagocytosis
first line defences
examples of specific responses
cell mediated response (T CELLS)
humoral response (B CELLS)
what response does t cells involve
cell mediated
what response does b cells involve
humoral
what is a pathogen
organisms that cause disease
- contain antigens on the surface so they can be identified and destroyed
what is an antigen
proteins that can generate an immune response when detected by the body
process of phagocytosis
- phagocyte is attracted to pathogen by its chemical products
- phagocyte and pathogen fuse together
- phagocyte engulfs pathogen forming a phagosome
- lysosomes then fuse with phagosome
- lysozymes hydrolyse bacteria
- products of hydrolysis are absorbed by phagocyte
- phagocyte becomes an antigen presenting cell
what is antigenic variation
process where a pathogen alters the shape of proteins on its surface and avoids a host response as memory cells no longer recognise the antigens
explain the cell mediated response
- macrophage ingests antigens and presents them to a T cell which divides them into 4 clones
- (killer, cytotoxic, memory and suppressor)
explain the humoral responses
- pathogen present in blood with a specific antigen
- complimentary antibody on B cell surface binds with antigen, takes it in and presents antigens on it’s surface
- helper T cell activates B cell
- B cells divide by mitosis (clonal expansion) to produce memory cells and plasma cells
what are the 4 cells T lymphocytes divide into (cell mediated response)
- helper T cells
- cytotoxic T cells
- memory T cells
- suppressor T cells
what is the role of memory B cells (humoral response)
remain in blood and will rapidly divide into plasma cells if antigen returns in future
what is the role of plasma B cells
release antibodies
what do T helper cells do
release cytokines that T cells, B cells and phagocytes respond to
what do cytotoxic T cells do
causes lysis of target cells and will destroy virus infected or cancer cells
what do antibodies do
form an antigen antibody complex which serve as markers for phagocytes to destroy attached cells
- have two binding sites so can clump cells together to make it easier for phagocytes to find - agglutination
what is an antibody
made of four polypeptide chains and are complimentary to only one antigen
- form an antigen antibody complex
what is active immunity
production of antibodies from the immune system in the presence of an antigen
what is passive immunity
introduction of antibodies from another person or animal
what is natural passive immunity
antibodies come from mother (through placenta or breast milk)
what is natural active immunity
being exposed to the antigen
what is active artificial immunity
acquired through a vaccine which stimulates immune system to produce antibodies
what is passive artificial immunity
antibodies are injected into the body
what is a vaccine
- dead or inactive form of a pathogen injected into the body to produce an immune response
what is herd immunity
the idea that if enough people within a population are injected the pathogen wont be able to be passed between hosts
why are vaccines not always useful
antigens on the surface of the pathogen can change so immunity is removed
ethical issues with vaccines
- testing could be done on animals
- expensive
- people should have an option
- must be tested on humans to detect toxicicity
what is monoclonal antibodies
many clones of a single antibody
structure of HIV
- lipid envelope embedded with attachment proteins
- genetic material and reverse transcriptase ( DNA > RNA ) found inside a protein capsid
how is HIV replicated
- binds to CD4 which is found on helper T cells
- capsid fuses with cell surface membrane
- RNA and reverse transcriptase enters the cell
- RNA is converted to DNA by reverse transcriptase, this moves into the nucleus
- HIV components are produced by the cell
how does an ELISA test work?
- enzyme attached to antibodies
- when reacts with certain substrate, a colour product is formed
- colour change shows antigen is present in the sample
why are antibiotics ineffective against viruses and HIV
- antibiotics work by preventing bacteria from forming cell walls so the bacteria can’t control the entry and exit of water so the cell bursts
- viruses don’t have a cell wall so are unaffected
how is HIV treated
antiretroviral drugs
how do antiretroviral drugs work
keep the levels of HIV in the blood stream very low, reducing the impact on the hosts immune system.
