6.3 Response to infection


Non-specific responses to infection

-Inflammation -->

  • occurs when an infection is localised
  • when tissue is damaged, mast cells and basophils release histamines
  • histamines cause arterioles to dilate, causing heat and tenderness
  • histamiens also make capillary walls leaky 
  • meaning plasma containing leucocytes and antibodies is forced out of the capillaries, causing swelling and pain
  • the antibodies disable the pathogens

-Fever -->

  • when a pathogen infects the body, the hypothalamus makes the body temp higher
  • most pathogens reproduce @ lower than 37 degrees C, so a higher temp means less pathogen reproduction
  • the immune system works better at higher temps so will be better at combating the pathogen @ a higher temp
  • if fevers get too high, they may denature some enzymes and this can lead to tissue damage and even death


  • a non-specific response involving  leucocytes
  • 2 main types of leucocytes are granulocytes and agranulocytes
  • neutrophils are granulocytes and can ingest only a few pathogens at a time and cannot renew their lysosomes
  • macrophages are agranulocytes that can renew their lysosomes and accumulate at the site of infection to attck invading pathogens
  • phagocytes engulf the pthogen and enclose it in a vesicle
  • the vesicle (phagosome) joins w/ the lysosomes and the enzymes in the lysosomes breaks down the pathogen]the phagocytes then produce cytokines that stimulate other phagocytes to move to the site of infection

Different kinds of lymphocytes

-B cells -->

  • are produced in the bone marrow
  • once mature, they are found in the lymph glands and free around the body
  • B cells have receptor proteins on their surface that are identical to the antibodies they will produce
  • when a B cell binds to an antigen it produces:
    • B effector cells= they divide to form the plasma cell clones
    • Plasma cells= they produce antibodies to particular antigens
    • B memory cells= they provide immunological memory to a specific antigen

-T cells -->

  • are produced in the bone marrow but mature and become active in the thymus gland
  • the surface of every t cell displays htousands of identical t-cell receptors
  • t cell receptors bind to antigens on the infected body cells and produce  different types of t cells:
    • T killer cells= produce chemicals to destroy the infected body cells 
    • T helepr cells= activate the plasma cells to produce antibodies agaisnt the antigens on a particular pathogen and secrete opsonins which label the pathogen for phagocytosis
    • T memory cells= are long lived cells that make up part of the immunological memory. When they meet a pathogen for a second time, they divide rapidly to produce large amounts of T killer cells

The humoral response

-reacts to antigens found outside of the body

-results in the production of antibodies

-T helper activation -->

  • duirng phagocytosis…


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