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13.4. The immune response

The immune response

The organism produces a specific or adaptive immune response against antigens depending on their nature.

  • Humoral immune response: when the infection is extracellular and the infectious agent is spreading through plasma or interstitial fluid. The B lymphocytes secrete antibodies.
  • Cellular immune response: when the infection is intracellular and the infectious agent reproduces within the cell. The T cells  are responsible for destroying the infected cells.

The immune response is characterized by its:

  • Specificity. A given lymphocyte or antibody acts specifically on a type of antigen that they recognize.
  • Diversity. It has many types of antibodies and lymphocytes capable of recognizing a wide variety of antigens. When a lymphocyte is activated, it reproduces by creating clones.
  • Self-tolerance. The immune system can recognize own from strange.
  • Immunological memory. When the body first comes into contact with a pathogen, it takes a few days for the adaptive response to be effective. But the immune system will produce memory lymphocytes and, the next time the body comes into contact with the pathogen, its response will be effective much sooner, without the symptoms of the disease manifesting.