Module 4.1 Communicable diseases

• What are some diseases caused by bacteria?

  Tuberculosis, ring rot(potatoes, tomatoes), bacterial meningitis
• What are some diseases caused by viruses?

  HIV, influenza, Tobacco Mosaic Virus(plants)
• What are diseases caused by protoctista?

  malaria, potato/tomato late blight
• What are diseases caused by fungi?

  black sigatoka(bananas), athlete's foot, ringworm(cattle)
• What are examples of direct transmission between animals?

  • Direct contact
  • contact with bodily fluids
  • skin to skin
  • sharing needles
  • Ingestion
  • taking in contaminated food or drink
  • transferring pathogens from hand to mouth
• What are examples of indirect transmission between animals?

  • Fomites: inanimate objects i.e. bedding, socks, cosmetics
  • Droplet infection: droplets of saliva from talking, sneezing and coughing
  • Vectors: they transmit disease from one host to another
• What are examples of primary defences against pathogens in animals?

  Skin, blood clotting, expulsive reflexes, the nose, eyes, ear, cilia and more
• What is the body's second line of defence?

  • Non-specific(innate)
  • inflammation
  • fever
  • phagocytes
  • Specific(adaptive)
  • immune system recognises the pathogen and produces specific antibodies( B cells and T cells)
• What are neutrophils?

  They are specialised white blood cells that have a multi-lobed nucleus.
• What are macrophages?

  They are specialised white blood cells that have a round nucleus. When a pathogen gets destroyed by a macrophage, its antigens combine with glycoproteins in the cytoplasm(MHC- Major Histocompatibility complex) and this takes the antigens to the cell surface membrane-now an APC(Antigen Presenting Cell) and can stimulate the specific response
• What are the roles of cytokines?

  Cell signalling and regulation of immune responses:

  • Macrophages release monokines. Some of these attract neutrophils(chemotaxis) and others stimulate B cells to differentiate and release antibodies
  • T cells and macrophages release interleukins, which can stimulate the clonal expansion and differentiation of B and T cells
  • Many cells can release interferon, which inhibits virus replication and stimulates the activity of T killer cells
• What are the role of opsonins?

  They are a group of antibodies that bind to the antigens on a pathogen. They then act as binding sites for phagocytic cells, so that these can more easily bind and destroy the pathogen.
• Describe the process of phagocytosis:

  1. The pathogen releases chemicals that attract phagocytes towards it along the concentration gradient
  2. When the phagocyte reaches the pathogen, it binds to the pathogen via complementary receptors recognising it as  foreign
  3. The phagocyte then engulfs the pathogen, encasing it in a vesicle. The resulting structure is called a  phagosome
  4. Lysosomes in the phagocyte move towards the phagosome and fuse or combine with it, forming a phagolysosome .
  5. They release lysozymes or enzymes which breaks down the pathogen through hydrolysis reactions.
• Describe what is meant by cell-mediated response?

  This is when Helper T cells divide by mitosis to become more helper T cells and differentiate which stimulate B cells and phagocytosis, or T memory cells or cytotoxic T cells.
• What are the different cells Helper T cells differentiate into?

  • Killer T cell
  • Helper T cell
  • Memory T cell
  • Regulator T cell
• What is a Killer T cell?

  aka cytotoxic T cells

  They kill infected body cells by releasing perforin -this protein creates pores in the cell surface membrane which causes the cell to shrivel or lyse
• What is a Helper T cell?

  They help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells
• What is a Memory T cell?

  They remain in lymph nodes to respond rapidly.

  They cause a faster immune response = produces antibodies more rapidly
• What is a regulator T cell?

  They slow down and stop the immune reaction after about 1 week.