The Specific Immune Response

The Specific Immune Response

  • The specific immune response, also called the adaptive or acquired immune response, targets specific pathogens using specialized lymphocytes: B cells and T cells.

Antigen Recognition

  • Each B or T cell is programmed to recognise a particular molecule, or antigen, found on the surface of a pathogen.
  • An antigen is any substance that can incite an immune response.

Activation of Lymphocytes

  • When an antigen is identified, the corresponding B or T cell proliferates rapidly in a process called clonal selection.
  • The newly produced B or T cells attack the specific pathogen that expressed the antigen that triggered their activation.

Actions of B Cells

  • B cells are involved in what is known as the humoral response.
  • When activated, B cells transform into plasma cells that produce antibodies specific to the identified antigen.
  • Antibodies lock onto antigens on the pathogen’s surface, marking it for destruction, neutralising it, or causing it to agglutinate (clump together).

Actions of T Cells

  • T cells are involved in the cell-mediated response.
  • Cytotoxic T cells directly destroy infected cells by identifying proteins on their surface.
  • Helper T cells aid in the immune response by stimulating the production of B cells and cytotoxic T cells.

Memory and Future Response

  • Both B and T cells can become memory cells after an infection, conferring immunity to that specific pathogen.
  • If the same pathogen enters the body again, these memory cells quickly recognise its antigens and respond much faster than the first time.
  • This memory mechanism underlies the workings of vaccination, where a harmless form of the pathogen is introduced to stimulate an immune response and the production of memory cells.