January 23, 2008

The Scent of a Pathogen

sort by pattern to killOur immune system, the defense ministry of our bodies, tackles extraneous foreign molecules in a variety of ways. It may produce highly specific antibodies which fight against specific pathogens, as an example of 'adaptive immunity'. Or it may act then and there by virtue of 'innate immunity'.

Adaptive immunity takes some time to develop : due to the processing and presentation of antigen and the subsequent production of antibodies. Innate immunity, on the other hand, is inborn: encoded in the genome. They have broad specificity, meaning that one soldier (receptor) can kill a variety of organisms only if they fitted a certain criterion.

This is exactly how innate immunity handles pathogens. The soldiers (cells) in charge of innate immunity first detects the telltale signature trail of the pathogen: PAMPs or Pathogen Associated Molecular Pattern. Some of the examples of this molecular pattern are LPS (lipopolysaccharide of Gram negative bacteria which serves as endotoxin), peptidoglycans of Gram positive bacteria and flagellin of bacterial flagella. These soldiers seek the scent (motif) of the pathogens and sniff them out.

Frequently, these molecules have some mannose (a carbohydrate) residues in them and they are promptly recognized by pathogen recognition receptors. These receptors may be found in the circulation, in soluble form; may be PAMP receptors in macrophage cells, cells in charge of killing and engulfing invaders or may be Toll like receptors, present in macrophages and dendritic cells. Wherever they are located they just look for the signature thumb prints, latch onto them to give them the death kiss. These patterns are shared by more than one pathogen, it will identify and kill 'em all as per its recognition algorithm.

I can't help but mention Lavasoft's adware software in this regard. This antispyware software program looks for unwanted cookies in your hard disk in much the same way. It uses a protocol called code sequence identification to recognize telltale patterns based on its database of past records. You may download the program for free (if you click the link) but how about the physiological program we inherited from our ancestors, more importantly who programmed it?

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