Nonspecific immunity

Nonspecific immune mechanisms (also innate', natural', non-adaptive) are innate. This means that all necessary information is invariably written in DNA and already present in the zygote. Nonspecific immunity responds after each encounter with an antigen by the same mechanisms, has no memory'.

It consists mainly of complement components and phagocytes. It is not aimed at the destruction of a specific antigen, but it is very fast. The cells are constantly present in the blood, so that activation is almost instantaneous (minutes to hours) when needed.

It is evolutionarily older (in all multicellular organisms to varying degrees) than specific immunity. It consists of cellular and humoral components.

This group also includes barrier functions of the body', i.e. skin, mucous membranes, etc. (generally structures that prevent foreign particles from entering the body).

Aggregation of the components of natural immunity

Cellular components

• 'Phagocytes',
  • neutrophils (microphages) - short-lived, not APCs,
  • monocytes - their tissue form = macrophages - they live for a long time,
  • dendritic cells and other APCs,
  • eosinophils,
• 'mast cells' (mast cells, heparinocytes),
• basophily,
• 'NK-cells',
• 'thrombocytes'.

Humoral components

• 'Complement' and 'acute phase proteins,
• 'coagulation and 'fibrinolytic system'
• interferons.

Cellular component

These include mainly granulocytes, macrophages and some lymphocytes. Thrombocytes may also be included, but play a minor, but not unimportant, role.

Granulocytes and macrophages

The bulk of the cellular component of non-specific immunity is composed of cells arising from the myeloid lineage. This includes cells that exhibit high phagocytic capacity, i.e. macrophages and neutrophil granulocytes. Antigen-presenting cells, which include mainly dendritic cells (cooperating with T-ly) and follicular cells (presenting Ag to B-ly), cannot be overlooked. This group also includes eosinophils' and basophils'.

Lymphocytes

The next part is the cells of the lymphoid line. These include mainly cytotoxic NK cells (natural killers). Some immunologists also include some B-lymphocytes in this group due to their independence from T-lymphocytes and the possibility of partial change of their specificity during proliferation. These are B-cells that recognize carbohydrate antigens.

Humoral component

Acute phase proteins

This is a group of proteins whose levels rise significantly and relatively quickly after the immune system is activated. Complement components are also included here, but are separated for clarity.

 For more information see Acute Phase Proteins.

Complement

Complement is a set of serum proteins capable of inducing lysis of certain cells when activated.

 For more information see Complement.

Cytokines

Cytokines are a very diverse group of signal peptides, some of which have a hormonal function. Their production varies significantly with the degree of cell activation. They mediate communication between cells of specific and non-specific immunity. We divide them into several subgroups:

• interleukins,
• chemokines,
• interferons.

 For more information see Cytokines, Interleukins, Chemokines, Interferons.

Principles of non-specific mechanisms

Identification of pathogenic patterns

Pathogens are identified by the presence of PAMP (Pathogen-Associated Molecular Pattern) - phylogenetically highly conserved structures. They are carried only by microorganisms and are essential for their survival. They include:

• bacterial wall' - peptidoglycan, lipoteichoic acid, lipopolysaccharide,
• bacterial DNA' - lots of cytosine and guanine, no methylation,
• 'dsRNA' - viral.

These patterns are recognized by the PPR (Pathogen Pattern Receptor) = PRR' (Pattern Recognition Receptor). They are of the following types:

• secernated' - opsonins (e.g. MBL) of complement activation,
• endocytic' - on phagocytes, mediate phagocytosis (e.g. MMR (mannose macrophage receptor), MSR (macrophage scavenger receptor) - cleans up bacterial debris),
• signalling' - activate a signalling pathway leading to the production of cytokines (e.g. TLR (Toll-like receptor)).

Identification of endogenous patterns

In the context of apoptosis, ACAMP (Apoptotic Cell Associated Molecular Pattern) patterns are exhibited - e.g., phospholipids of the inner layer of the cell membrane. They are recognized by the ACR (Apoptotic Cell Receptor), rather anti-inflammatory cytokines are produced.

Antigen presentation

Antigen Presenting Cells (APCs) engulf antigens, process them in lysosomess and present them on HLA class II molecules. Thus processed, antigens (or antigenic epitopes) are presented together with costimulatory signals to T-lymphocytes.

Note: If any cell, not just the antigen presenting cell, is infected with an intracellular parasite, the antigen is presented on HLA Class I.

Links

Related articles

• Specific Immunity
• Immune system
• Macrophages
• Neutrophil granulocytes
• Compliment

References

• 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.

• ŠTERZL, Ivan. Základy imunologie. 1. edition. Praha : Karolinum, 2005. ISBN 80-246-0972-X.

• ŠVÍGLEROVÁ, Jitka. Nespecifická imunita [online]. The last revision 2009-02-18, [cit. 2010-11-15]. <https://web.archive.org/web/20160416192854/http://wiki.lfp-studium.cz/index.php/Nespecifick%C3%A1_imunita>.