Lecture 9

\ Immune system is network of different organs and cells and tissues to protect the body from pathogens. Pathogens consist of viruses, protozoa, parasite, bacteria and fungi The order smallest to largest: Virus, intracellular bacteria, extracellular bacteria + protozoa, fungi, parasites Extracellular pathogens Streptococcus pneumonia – gram negative bacteria – causes pneumonia There are more than 90 different serotypes for streptococcus pneumonia, meaning we need 90 different antibodies.

Clostridium tetani causes tetanus via the release of tetanospasmin

  • a typical dose of tetanospasmin is too small to provoke an immune response

influenza is a type of intracellular pathogen viruses are always intracellular – they use human ribosomes and therefore looks a little human as it uses our machinery and therefore makes it difficult to attack by our immune system the immune system has to be adaptive to respond to mutated pathogens HIV contains yellow spike proteins which allows HIV to dock and enter the body Inside the matrix is the capsid, where there are 2 copies of RNA which has reverse transcriptase which allows copies of RNA and DNA to be made and duplicated in our cells.

The antigenic drift rate is so rapid that it outpaces development of an effective immune response and therefore its hard to develop vaccine for it People can have more than one HIV present within them as HIV changes very fast

  • evolves easily be genetic drift   influenza A can encode 8 genes with its 8 poeices of RNA   H1N1 started mutating and effecting humans. It manages to survive in human host and 8 pieces of RNA was transferred to human cells. This caused Spanish flu   Spanish flu was dangerous, however in 1957 another type of event occurred when 3 RNAs were transferred to cause Asian flu. H1N1 – H2N2   Then from that, 2 more RNA were transferred. H2N2-H3N2 in 1968 to cause the Hong kong flu
  • N proteins and H proteins are changing and we can develop more viruses   Antigenic shift/variation is another challenge faced by immune system   Initial infection, immune system develops response to get rid of pathogen. However, if pathogen alters their surface proteins, immune response can be avoided. Plasmodium falciparum.   When a person is bitten by plasmodium falciparum, the gametocytes in blood is transferred to mosquito vector. He gametocytes hacth out into gametes and zygotes and effect its gut, becoming sporozoites in salivary gland. Now when it bites another person the sporozoites enters another person and replicates in the liver and grow in the liver until they rupture the red blood celkl and release gameocyte in human.   Pathogens continue to change surface protein to evade immune system. The variant protein is encoded by VAR gene and the variant molecules alter protein surface.   Adaptive immune response is involved in the generation of antibodies to clear away pathogens.   It can take a week to gather antibodies to destroy pathogens. However, second exposure only takes 4 to 6 days to gather antibodies. It is faster and bigger   Primary and secondary response are slow, and therefore we rely on our innate immune response, which starts early on.   The immune system knows what to target by looking at non self cell structures, such as
  • Cell wall
  • Protein and peptide structures from pathogens
  • Yeast carbohydrate
  • Pathogen DNA
  • Viral antigen on host cells   Immune response also has to process altered self, such as malignant cells.   Tissue specific response   Different tissues display different immune responses   Too much use of immune response and we can damage the host   The humoral arm relies on barriers and chemical warfare and makes calls for help.   The cell mediated arm comprises a range of phagocytic cells and natural killer cells that destroy virus infected cells: all these respond to calls for help from the innate humoral arm

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