Response of Cells to the Pathogen, Various cells and proteins show response to the pathogen, these cells and proteins perform two major functions.
- Recognition of the pathogen,
- Cellular response to pathogen.
- Recognition of the pathogen:
Phagocytic cells have receptor molecules that recognize molecules present on the surface of pathogens. After the recognition of pathogens, the immune cells show response. The phagocytic cells possess many receptors. The most common receptors’ family is “toll-like receptors” (TLRs) which is a large family of receptors. About 10 TLRs have been identified in man, recognizing double stranded RNA (TLR-2 recognize it), lipopolysaccharide (it is present in the bacterial cell wall), lipoproteins (if it is an antigen), un-methylated DNA (that is; bacterial DNA, and is recognized by TLR-9 and flagellins (it is a protein in the flagella of the bacteria, and is recognized by TLR-5).
- Cellular response to pathogens:
The cellular response to the pathogens occurs in two ways.
- Production of new factors.
The neutrophils have the ability to only phagocytose smaller organisms. While macrophages have the ability to phagocytose smaller organisms, damage cellular pieces and also macro organisms.
Phagocytosis occurs in four steps. In first step attachment of the phagocytic cell to the pathogen occurs, in step 2, the phagocytic cell ingest the pathogen, in step 3 the ingested pathogen is killed and in the final step the remains of the pathogen are degraded by some proteolytic enzymes.
- Production of new factors:
In addition to phagocytosis the cells of innate immune system secrete certain molecules that modify the behavior and function of the other cells. Such factors may enhance the proliferation of the cells, the differentiation of the cells and secretion (by stimulating other cells). The new factors are known as cytokines. The common cytokines are; interleukins, interferons, colony stimulating factor, tumor necrosis factor and chemokines.
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