The immune system
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 ).
Structure of the immune system[edit | edit source]
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]
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]
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]
IS cells ( immunocytes ) = leukocytes , from bone marrow stem cells, having the adhesive molecule CD34. 2 baselines:
- 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 .
- 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.