The immune system

From WikiLectures

The immune system (IS) maintains the integrity of the body; recognizes harmful from harmless and thus protects the body from exo- and endogenous pollutants. Together with the nervous system and the endocrine system, they belong to the regulatory systems.

Basic concepts:

  • Immunity : protects the body against pathogenic microorganisms and their toxins.
  • Autotolerance : recognizes one's own tissues.
  • Immune surveillance : recognizes internal pollutants; removes old, damaged, mutated cells.
  • Antigens (Ag): substances that IS recognizes and responds to.

General characteristics of the immune system[edit | edit source]

Communication within the immune system[edit | edit source]

Communication between cells of the immune system takes place through signaling molecules :

  • as direct interactions of molecules in membranes ,
  • or via secreted molecules , including:
    • cytokines - protein molecules,
    • arachidonic acid derivatives ( eicosanoids ) - prostaglandins , leukotrienes , thromboxanes ,
    • NO ,
    • and more.

Typical characteristics of the functioning of the immune system[edit | edit source]

  • A single signal usually has no response (the presence of costimulatory signals is required, otherwise it usually leads to attenuation).
  • Signal amplification (the signal is amplified during the signal path).
  • Presence of signal transduction systems (termination of the immune response).
  • Cell proliferation (changes in cell number as needed).
  • Diffuse arrangement (high probability of encountering a stimulus) + cell migration (will allow the response to be targeted where needed).


local specificity of the immune response[edit | edit source]

Immune reactions take place mainly in mesenchymal tissues. Every reaction is associated with damage to its own structures! If the stimulus is on the mucosa, there is usually a decrease. If something enters the submucosal ligament, it is likely to be pathogenic and the response will take place (see mucosal immune system ). Immune-privileged areas are areas where some immune mechanisms are lacking. The immune response always damages the structures themselves, so these are areas with a low capacity for tissue regeneration (eg the CNS ).


Allografts do not heal in immune-privileged areas .

Structure of the immune system[edit | edit source]

B-cell activation by T-cell
Innate immunity

(also non- antigenically specific , congenital , non-adaptive )

cellular phagocytes
macrophages
NK cells
humoral complement
interferons (IFN)
Specific immunity

(also acquired , adaptive)

Cellular T-lymphocytes
humoral B-lymphocytes → [[antibodies]

Innate immunity[edit | edit source]

Searchtool right.svg For more information see innate immunity.

Recognizes dangerous from harmless by PAMP (Pathogen-Associated Molecular Pattern) - phylogenetically conserved molecules that are typical of pathogens (eg viral RNA , lipopolysaccharide ).

It cooperates with specific immunity (gives information about what is dangerous).


Specific immunity[edit | edit source]

Searchtool right.svg For more information see Specific immunity.

T-lymphocytes recognize only linear peptide fragments processed and presented by antigen presenting cells (APC), especially dendritic cells in the presence of costimulatory signals. They help non-specific immune cells kill pathogens.

B-lymphocytes recognize the native antigen and receive costimulation from T-lymphocytes.

Autoreactive lymphocytes are eliminated.

Specific immunity reacts only against dangerous stimuli (non-specific immunity and probably tissues that are damaged by the pathogen provide information about this). It has immunological memory (use in active immunization ).

Major components of the immune system[edit | edit source]

Immune responses are provided by different types of cells and molecules and their interactions. Cells of the immune system + connective tissue cells → lymphatic tissue, lymphatic organs.

cells of the immune system[edit | edit source]

Hematopoesis

IS cells ( immunocytes ) = leukocytes , from bone marrow stem cells, having the adhesive molecule CD34. 2 baselines:

  1. Myeloid
    • Monocytes ( macrophages ), neutrophils , basophils ( mast cells ), eosinophils , dendritic cells → non-specific component of IS; ability of phagocytosis , producers of cytokines , soluble mediators.
    • Dendritic cells, monocytes and macrophages = antigen presenting cells (APC); basis and antigen-specific part of IS.
    • The myeloid lineage also includes erythrocytes and platelets .
  1. Lymphoid
    • NK cells , B and T lymphocytes .
    • B-cell development takes place in the bone marrow and is completed after encountering Ag in secondary lymphatic organs; the end stage is antibody -producing plasma cells .
    • The development of T-lymphocytes takes place mainly in the thymus ; 2 main phenotypically distinct subpopulations: helper cell precursors (CD4 receptor surface), cytotoxic cell precursors (CD8): after encountering Ag on the surface of suitable APCs, they differentiate into mature effector T cells.
    • After encountering Ag, some T and B lymphocytes differentiate into memory cells, which are then responsible for immunological memory.


The basic molecules of the immune system[edit | edit source]

  • TCR, BCR (antigen-specific receptors on the surface of T and B lymphocytes);
  • MHC I., II. ( HLA molecules);
  • Fc receptors (bind Fc portions of immunoglobulin molecules);
  • adhesive and costimulatory molecules;
  • immunoglobulins;
  • cytokines;
  • components of the complement system

Physical barriers[edit | edit source]

  • Easy renewal of surface layers (pathogens disappear together with epithelia).
  • Various surface molecules, secretory antibodies (prevents adherence of pathogens).
  • Commensal microorganisms (competing with pathogens).

Links[edit | edit source]

Related articles[edit | edit source]

External links[edit | edit source]

References[edit | edit source]

  • HOŘEJŠÍ, Václav – BARTŮŇKOVÁ, Jiřina. Základy imunologie. 3. edition. Praha : Triton, 2008. 280 pp. ISBN 80-7254-686-4.
  • KREJSEK, Jan – KOPECKÝ, Otakar. Klinická imunologie. 1. edition. Hradec Králové : Nucleus HK, 2004. 941 pp. ISBN 80-86225-50-X.