ISSN: ISSN: 2329-8790
Immunity is typically taken to be the defense that one organism projects against injury from another biological organism, such as infection or parasitization. However, the mechanisms of immunity against biological organisms are fundamentally the same as those that protect an organism from stress and injury of all sorts, including biological, physical and chemical. Any organism’s first line of defense against infection, or other insult, is a physical barrier that delineates self from non-self. Evolution has produced many systems to augment and repair barrier immunity when, inevitably, it is breached. Among these systems are molecules that exist pre-formed in the fluid phase and are instantly available to make temporary patches and initiate long-term healing. Serine protease cascades have arisen as a common mechanism for such systems. Beginning from a primordial molecular with mixed functionality including elements of coagulation, and coagulative targeting of foreign bodies including biological infection, distinct pathways have formed. The coagulation cascade, which helps to maintain the integrity of numerous tissues, including the vascular system, is among the more essential of these systems. Other phylogenetically derivative pathways have arisen, including innate immune systems, that play allied roles in the maintenance of organismal integrity, and which therefore interact extensively with the coagulation systems. In this sense the coagulation system and related, derivative pathways are molecular extensions of barrier immunity that are essential for the maintenance of homeostasis.