immune system

• HIV infects the immune system by replicating inside the T helper (TH) cells
• the glycoproteins on HIV binds to the receptor proteins on the cell surface membrane of the t helper cells
• the capsid is injected into the t helper cells. The RNA and integrase and reverse transcriptase enzymes are released from the capsid
• reverse transcriptase

  converts single stranded HIV RNA into double stranded DNA
• the DNA moves to nucleus of T helper cell
• integrase


  enzymes that inserts HIV DNA into T helper cell DNA
• the genes in HIV DNA are expressed in the t helper cells. His proteins are synthesised and new HIV RNA is made
• new HIV viruses are released from the t helper cells. the t helper cells die. the HIV viruses can infect more cells
• antiviral drugs can be designed to target the reverse transcriptase enzyme
• fixing of antigens

  the antigen for the infection that is being tested for is immobilised in the beaker
• addition of blood


  a sample of blood that is being tested for is added to the beaker. the antibodies in the blood will bind to the antigens and form many antigen-antibody complexes
• the beaker is washed out so the unbounded antbodies are removed
• secondary antibodies are added. these antibodies have enzymes. if the sec. antibodies bind to the antibodies from the blood the enzymes will change the colour of a solution
• the primary response is slow because it rakes time for the antigens to be detected and the specific plasma cells to be activated
• the individual is likely to show symptoms during the primary response. The pathogen has time to cause harm before it is removed
• memory cells produced by t and b cells remain in the body after the infection has been removed
• secondary response is faster- presence of memory cells. they can quickly identify the antigens and produce the correct antibodies
• the secondary response is stronger- more plasma cells can be produced more quickly