Non-specific immunity

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

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

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

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

Cellular components

 * Phagocytes,
 * Neutrophils (microphages) – live for a short time, not APC.
 * Monocytes - their tissue form = macrophages – live for a long time,
 * Dendritic cells and other APCs,
 * Eosinophils,
 * Mast cells (heparinocyte),
 * Basophils,
 * NK cells,
 * Thrombocytes.

Humoral components

 * Complement and acute-phase proteins,
 * Coagulation and fibrinolytic system
 * Interferons.

Cellular component
These mainly include granulocytes, macrophages and some lymphocytes. Platelets can also be included here, but they play a minor, but not unimportant, role.

Granulocytes and macrophages
The predominant part of the cellular component of non-specific immunity consists of cells derived from the myeloid lineage. These include cells that have a high phagocytic capacity, i.e. macrophages and neutrophilic granulocytes. Antigen-presenting cells, especially dendritic cells (cooperation with T-lymphocytes) and follicular cells (presents Ag to B-lymphocytes), cannot be neglected either. This group also includes eosinophils and basophils.

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

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

Complement
Complement is a set of serum proteins that, when activated, can induce the lysis of some cells.

Cytokines
Cytokines form a very diverse group of signal peptides, some of which also have a hormonal function. Their production changes 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.

Identification of pathogenic patterns
Pathogens are identified by the presence of PAMP (Pathogen-Associated Molecular Pattern) - phylogenetically highly conserved structures. Their carriers are only microorganisms and are essential for their survival. Is part of them:


 * bacterial wall - peptidoglycan, lipoteichoic acid, lipopolysaccharide,
 * bacterial DNA - a lot of cytosine and guanine, without methylation,
 * dsRNA - viral.

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


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

Identification of endogenous patterns
In connection with apoptosis, ACAMP (Apoptotic Cell Associated Molecular Pattern) patterns are exhibited - e.g. phospholipids of the inner layer of the cell membrane. ACR (Apoptotic Cell Receptor) receptors are recognized, and rather anti-inflammatory cytokines are produced.

Antigen presentation
Antigen Presenting Cells (APCs) absorb antigens, process them in lysosomes and present them on HLA class II molecules. In this way, the antigens (or antigenic epitopes) are presented together with the costimulatory signals to the T-lymphocytes.

Note If any cell, not just the antigen presenter, is infected with an intracellular parasite, the antigen is presented to HLA class I.

Related Articles

 * Specific immunity
 * Immune system
 * Macrophages
 * Neutrophilic granulocytes
 * Complement