Innate Recognition of Pathogens

In the initial stage of immune response, the innate immune system recognizes the presence of pathogens and provides the first line of defense.Dendritic cells which are circulating through the tissue has the ability to recognize presence of pathogen associated molecular patterns or PAMPs.PAPMs are conserved features of pathogens such as lipopolysaccharides (LPS) that are components of the cell membrane of all gram-negative bacteria.Dendritic cells have the ability to recognize PAMPs through the expression of family of Toll like receptors (TLRs).

In the case of LPS it is recognize by TLR4 receptor, which is expressed in the surface of dendritic cells.

LPS is transported by a soluble LPS binding protein (LBP) to the surface of dendritic cells, And it’s deposited in cell surface protein (CD14).The presence of LPS is detected by TLR4 though its interaction and recognition of the LPS bound CD14.The signal delivered by TLR initiates maturation of dendritic cell.

Dendritic cell can now migrate to regional lymph nodes and activate required immune response.