Prrs

PRRs are expressed on various antigen-presenting effector cells such as macrophages, dendritic cells, basophilic and eosinophilic granulocytes and NK cells. They are also found on resident tissue cells such as keratinocytes, fibroblasts and endothelial cells. PRRs on cell surfaces (pattern recognition receptors) include:

• Toll-like receptors (TLR)
• Type II lectin receptors
• Integrine.

In addition to the system of toll-like receptors (TLR), which recognizes PAMPs (pathogen associated molecular patterns) on the cell surface or in vesicles of cells, cytoplasmic PRRs are also described. The discovery of these receptors was based on the assumption that intracellularly invaded pathogens cannot be detected via membrane-bound receptors to trigger an immune response.

These cytosolic receptor families include:

• the RLRs (Retinoic acid-inducible genes I (RIG-I)-like receptors
• NOD-like receptors (nucleotide-binding oligomerization domain like receptors, in short NLRs).

In innate immunity there are only a few (analogous to PAMPs), conserved PRRs, which have been formed and selected during evolution and can be expressed together on one cell.