The Immune System
The immune system is unknowable. ~ American clinician Steven Deeks
To detect and destroy microbial invaders, an immune system covers 2 territories: cells and the extracellular pathways of the body, including the circulatory system. The pathways are patrolled by special agents of the immune system.
The human body incorporates innate immune responses evolved in the earliest multicellular organisms. Individual cells have their own defenses.
The evolution of immune systems has meant a layering of newer mechanisms on top of earlier ones. The vertebrate immune system is commonly considered bifurcated – based upon evolutionary emergence – into innate and adaptive (acquired) immunity subsystems. The significant distinction is aptitude for learning.
Innate immunity mechanisms are ever vigilant. Nonspecific antimicrobial systems are reflexive, in that their operation does not require prior contact with an infectious microbe.
Innate immunity, honed from hundreds of millions of years of evolution, requires no learning to work. That puts a quicker, though not always as effective, finger on the trigger.
In responsive flexibility, natural killer (NK) cells are the crowning achievement of the innate immune system. NK is an evolutionary bridge to adaptive immunity. NK cells are themselves adaptive: remembering their encounters and mounting pattern-sensitive (antigen-aware) secondary responses.
To keep up with evolving threats, acquired immunity gained the ability to learn and remember literally millions of new pathogens. All vertebrates have natural killer cells and acquired immunity.
Adaptive immunity is a learned response, able to ferret out pathogens that the innate system leaves alone. Adaptive response acts as a safeguard against the risk of attacking oneself, or when the innate system is not sufficiently effective in countering an attack.
Acquired immunity is layered on, and yet still dependent upon, innate immunity. Thus, the human bodily response to attack from pathogens is an interdependent orchestration of mechanisms. Almost every immune response is checked by using a dual signal code before allowing activation. A constant feedback system between the command chains and effector cells ensures an appropriate response that ends when the threat is extinguished.
The nervous and immune systems are the two most complex systems in the body. That complexity is amplified by the fact that each influences the other, as they constantly exchange messages in response to environmental and internal cues. ~ American science writer Richard Robinson
When the body is under attack, the immune system sends RNA-based information to the intelligence system and other parts of the body to synchronize response. This RNA influences gene expression, and so alters cellular operations.
A belly laugh increases the ability of your immune system to fight infections. ~ English American actress Elizabeth Taylor