immunology

• what molecules stimulate an immune response?

  pathogens

  abnormal body cells

  cells infected with viruses

  toxins
• definition of an antigen

  foreign protein that stimulates the production of antibodies
• describe the process of phagocytosis

  • a phagocyte engulfs/digests pathogen
  • which forms a vesicle called a phagasome
  • which fuses with a lysosome
  • bacteria is then destroyed by lysozymes or other hydrolytic enzymes
  • phagocytosis can result in production of antigen presenting cells (macrophages) where antigens are presented on the cell surface mebrane
• what is antigenic variability?

  type of genetic drift

  mutation in DNA or RNA that can alter tertiary structure of antigen allowing it to bind to a differant receptor

  when this occurs pathogens may not be recognised by memory cells from primary response so no secondary response
• what is the cellular response to ?

  T lymphocye to a foreign antigen
• describe the cellular response

  when an antigen presenting cell as been invaded by a pathogen and is displaying the antigen on its cell suface membrane

  • clonal selection takes place where a specific lymphocyte binds to presenting antigen and is selected to be cloned
  • this antigen is presented to a specific T lymphocyte
  • T cell is activated dividing rapidy by mitosis and these differntiate into multiple cell types
  • main one is the helper T cell which bind to antigen
• what do helper T cells do?

  stimulate.....

  cytotoxic T cells = kill infected cells via apoptosis

  B cells = divide many times by mitosis producing many clones which differntiate into plasma cells that release antibodies and memory cells that respond and release antibodies more rapidly

  phagocytes = helpter T` cell releases chemical called cytokines that attract phagocytes and B cells to area of infection
• what is the humoral response?

  response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies
• describe the humoral respone

  1 - antigen is presented by phagocyte/macrophage to helpet T lymphocyte

  2 - the helper T cell binds to and activates specific B lymphocyte with a complementary antibody = clonal selection

  3 - B lymphocyte is activated and divides via mitosis producing amny clones = clonal selection

  4 - these clones differentiare into 2 cells

  • plasma cell
  • memory cell
• what does the plasma cell do?

  secrete antibodies to antigen = short lived
• what does the memory cells do ?

  remain in the body to give a rapid reponse incase of a reinfection = lifelong immunity
• give two feature that the 2 cells have after clonal expansion/differentiation?

  many rough endoplasmic reticulums

  many mitochondiras for energy to form peptide bonds
• definition of an antibody

  is a protein specific to an antigen secreted by the plasma cell
• describe the antibody structure

  4 polypeptide chains

  2 long chains

  2 short chains

  2 variable binding site regions

  and 2 constant regions

  disulfide bridges to hold together
• they are proteins that have ......

  specific tertiary structure each with a differant binding site that is complemetary to one specific antigen

  forming antigen antibody comple
• what happens when an antigen antibody complex is formed?

  destruction of antigen
• what is agglutination?

  where antibodies bind to an antigen acting as markers for phagocytosis

  they cause clumping of the pathogen

  attracting phagocytes to engulf and hydrolyse bacterial cell
• what is the primary immune response?

  when you are infected with a pathogen for the first time

  non specific and specific immune response
• why is the primary respnse slow?

  takes time for the correct B cell to be activated via clonal selection and then divide and differentiate into lots of plasma cells and memeory cells via clonal expansion to produce antibodies with complementary shapes to the antigen

  person will experience symptoms
• what is the secondary immune response?

  if you are re infected with same pathogen in the future the T and B memory cells will recognise the antigen and start dividing
• describe process of the secondary immune response

  • T memory cells will divide into T killer cells to kill any cells that are infected by pathogen
  • B memory cells will divide into plasma cells to produce many antibodies which are complemetary to the antigen
  • no symptoms
• what are the differant roles of T memory cells and B memory celss i.the sencondary immune response?

  T memory = T killer cells

  B memory cells = divide into plasma cells to create many antibodies
• what does autoimmune mean?

  persons immune system attaks their own cells/proteins targeting them for destruction

  eg rheumatoid arthiritis
• what does the use of vaccinations provide?

  protection for individuals and population against disease

  uses to increse herd immunity to reduce the spead of disease through a population
• what happens when vaccination rates fall ?

  loss of herd immunity

  increases the likelihood to diseased people encountering non vacinated people
• describe the process of vaccine?

  • vaccine contains antigen from the pathogen
  • this antigen is displayed on the suface of the antigen presenting cell (macrophage or B cell)
  • a specific helper T cell with complementary receptor protein binds to the natigrn and activates a specific B cells using cytokines
  • the specific B cell divides via mitosis to form clones which differantate into plasma cells = prodice large amount sof antibodies
  • some B cells become memory B cells that produce plasma cells and antibodies more rapidy
• what is the structure of HIV?

  RNA

  reverse transcriptase

  proteins capsid

  phospholipid bilayer/evolope

  attachment proteins
• describe HIV repicarion in helper T cells

  • attachment proteins attach to the receptors
  • RNA enters the cell
  • RNA is converted to DNA via reverse transcriptase
  • DNA is inserted into T helper cell DNA and is transcribed into HIV mRNA
  • the HIV mRNA is transalted into new HIV protein and assembled into viral particles witch are then release by from the cell
• how does HIV cause the symptoms of AIDS?

  HIV infects T helper cells known as CD4

  when levels of these cells decrese as they are destroyed the viral load of viral particles increse then the person has developed AIDS

  less or no natibodeis eill be produced due to the destructuon of the T helper cells

  so fewer B cells activated to undergo mitosis and differnetiate into plasma cells
• what is active immuity?

  production of antibodies and memory cells by the pateints own immune system
• what is passive immunity?

  introducing antibodies from another source

  artificially acquired or naturally acquired
• example of passive immunity via antivenom

  when person is bitten the snake injects toxin into the person

  antivenon is injected as a tratment and it contains antibodeies against the snakes toxins which bind to toxin and target it for destruction
• active immunity :

  involves memory cell production

  involves plasma cell and antibody production

  long term

  can take time to develop
• passive immunity :

  no memory cells produced

  does not invole the production of plasma cells or antibody

  antibodes are introduced into the body from an outside source

  short term

  fast acting
• why are antibiotics ineffective against viruses?

  antibiotics kill bacteria by targeting bacteria specific enzyme or organelles

  they are ineffective against viruses due to the virus using the host machinery to replicate as viruses are acellular
• why cant antibiotics destroy viruses?

  they do not have peptidoglycan cell wall only a capsid

  and antibiotics work by breaking the peptidoglycan cell wall of the bacteria so they get osmotic lysis to kill them
• what is a monoclonal antibody?

  antibodies with the same tertiary structure produced from clones plasma cells

  threy can be used to target medecine to specific cells by attaching a theraputic drug to an antibody based on the cells antigens/receptors
• is it ethical to compare new medication agains a placebo?

  no as cases of disese such as cancers are left untreated

  the standard is to compare to current standard treatment for the condition
• what are the ethical issues associated with vaccines and monoclonal antibodies?

  treatment may cause death/it is risky

  use of animals for production may cause harm to the animal

  human trials the side effects are unknown
• what is the ELISA test used for?

  they are used to detect antigens or antibodies in a pateints bodily fluid (usually blood) using monoclonal antibodies