Themes > Science > Life Sciences > General Biology > Immunology > The Immune System & Its Effector Mechanisms > The Human Immune System & The Immune Response > The Human Immune System & The Immune Response

The Human Immune System
  1. The essential role of the immune system is the defense against disease: 'Self" vs. "non-self'.
  2. Organs, cells, and proteins constitute the system and antigens are the molecules and organisms to which it responds.
  3. The derivation of the immune system cells - macrophages T-lymphocytes and B-lymphocytes, and memory calls is from bone marrow stem cells.
  4. The immune response involves antigen recognition and processing, T-cell activation (cellular response), B-cell activation (humoral response).
  5. The structure of the protein of the immunoglobulin antibody molecule includes two identical but variable binding domains and a common region.
  6. Genetic recombination provides essential diversity of antibodies and T-cell receptors.
  7. Clonal selection provides essential biological economy.
  8. Vaccines are pseudo-antigens which prime the immune system.
  9. The immune system sometimes does not differentiate well between 'self' and 'non- self' resulting in autoimmune diseases.
  10. Allergies are an over-response of the immune system.
The Immune Response
  1. The immune system has evolved as the body's means of recognizing and destroying foreign materials and infectious agents (non-self or antigenic materials)
  2. The system includes circulating proteins (antibodies and lymphokines), circulating cells (macrophages, T and B lymphocytes, and others) and organs (bone marrow, thymus, lymph nodes and the lymphatic and blood circulatory system).
  3. The immune response starts with the ingestion of foreign material by phagocytic cells (e.g. macrophages) which then display both antigenic peptides and MHC (= HLA) self-recognition receptors on their cell membranes.
  4. The displayed antigens can then trigger:

     

    1. a cellular response, the proliferation of specific T-lymphocytes which recognize the antigen and,
    2. a humoral response, the proliferation of specific B-Iymphocyte which produce antibodies to the antigen.
  5. The immune response is directed by the T-4 "helper" lymphocyte which through direct interaction or through lymphokine messenger proteins (interleukins) mobilize both the cellular (cytotoxic T-cells, natural killer cells, etc.) and the humoral (B-lymphocyte, plasma cell antibody production) responses and the production of specific T and B memory cells. The response is limited by the T-8 suppresser cells.
Information Processing in the Immune System
  1. Information in the immune system involves both the DNA based generic information and highly specific cell surface protein receptors.
  2. There are three major problems which had to be solved as the immune system evolved:

     

    • A. The system had to recognize an almost infinite number of different molecular structures as being antigenic.
    • B. The system had to recognize the body's own protein as "self", not being antigenic.
    • C. The system had to be economically sound and only mobilize a response to a current antigenic agent.
  3. A tremendous level of T-cell receptor and antibody diversity (~ 108 different specific cell lines) is generated by DNA recombination and RNA splicing of a limited number of genes coding for different parts of the antigen binding site in each cell.
  4. The activities of those cells which might attack "self-antigens" is suppressed or destroyed during the development of the immune system in infancy. A failure of this process can lead to auto-immune diseases.
  5. The Clonal Selection mechanism provides that each antigen-specific cell line will only become turned on to proliferate and participate in the immune response only when it is exposed to its antigen.