Question

a.       Explain why the nervous system is described as “immunologically privileged,” and discuss whether this provides a beneficial or disadvantageous effect in this system.

b.      Discuss the defenses a pathogen encounters as it attempts to gain entry into the nervous system.

Answer 1

Please find the answers below:

Answer a: The nervous system is described as "immunologically priviliged" in the sense that it is delineated from the rest of the body when the immune reactions are started. The brain is a vital and highly sensitive organ and hence requires protection not only from external pathogens, but also from body's own cell-destructive mechanisms such as immune response. Hence, the human brain and the nervous system has evolved in a manner that some anatomical and physiological barriers protect it from body's immune response, such as presence of meninges, blood-brain-barreir or BBB, presence of cerebrospinal fluid or CSF etc. Together, these entities protect the terminally differentiated nervous cells from damage.

Answer b: There are various defenses a pathogen would encounter while attempting entry into the nervous system as enlisted below:

1. The protective meninger act as a physical barrier to prevent entry into the cranium and nervous system
2. The BBB itself acts as one of the major circulatory barrier for entry of pathogens and un-necessary cellular components
3. The brain and the nervous system is equipped with its own macrophage-type cells to evade the pathogens.
4. The body's immune response has been evolved in a manner that it itself prevents entry of any pathogens in the nervous system by cellular and humoral immune responses.