The system of organs of hemopoiesis and immunogenesis

The system of organs of hemopoiesis and immunogenesis

• A complex of specialized parenchymal organs (red bone marrow, thymus, lymphatic nodes, spleen) and structures formed by lymphoid tissue associated with the surface of the hollow organs of the digestive tract, respiratory, excretory, and reproductive systems.
• It participates in the interrelated processes of hemopoiesis and immune protection of the body.

Basic concepts and terms

Antigens

• Foreign proteins and substances of non-protein nature (lipopolysaccharides, nucleic acids, etc.) belonging to living organisms, tissues and cells genetically differing from the body (microorganisms and products of their vital activity, cells and tissues of transplants, genetically modified own cells).
• They provoke protective reactions to be recognized and eliminated.
• Specificity is their feature, resulting from antigenic determinants in their molecules. — epitopes.

Antibodies

• These are immunoglobulins of different classes (IgA, IgD, IgE, IgG, IgM), forming when antigens appear in the body to circulate in tissue fluids, blood, and lymph.
• They are synthesized by B cells and plasma cells.
• They have sites to bind cells (Fc fragment) that and can act as membrane receptors for antigens.
• Their antigen-binding site serve to selectively recognize antigen epitopes and ensure their inactivation.

Immunity

• Evolution-derived method to protect the body by:
  • preventing of antigen ingestion;
  • neutralizing and destructing antigens that have already entered the body, as well as own modified cells and and macromolecules.
• It is provided by the formation and interaction of nonspecific and specific immune reactions.

Nonspecific immune response (innate immunity):

• is a congenital protective system, which is provided by:
  • mechanical factors (epithelial barriers, mucociliary transport, etc.);
  • biological factors (competition of "own" and "foreign" microorganisms);
  • chemical factors (for example, low pH of gastric juice);
  • humoral factors (antimicrobial substances in secretions, blood and tissue fluids);
  • phagocytic and non-phagocytic mechanisms of cell activity (granulocytes, mast cells, macrophages, NK cells, B₁-cells);
• It develops in the first minutes or hours after the pathogen entering the body;
• does not provide immunological memory;
• serves to develop a specific immune response.

Specific immune response (acquired/adaptive immunity):

• occurs as a result of specific recognition of foreign or own modified antigens with subsequent induction of:
  • humoral immune response — antibody production by effector cells;
  • cellular immune response — the contact interaction of effector cells with target cells carrying foreign or modified own antigens;
• develops slowly (7–10 days) and is accompanied by:
  • selection of immunocytes that recognize foreign and do not react to their own antigens;
  • rearrangement of genes, encoding antigen-recognizing antibody loci;
  • formation of clones of activated immunocytes;
  • formation of memory cells.