Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") but some people are born with defects in the immune system, or primary immunodeficiency. A person who has an immunodeficiency of any kind is said to be immunocompromised. An immunocompromised person may be particularly vulnerable to opportunistic infections, in addition to the normal infections that can affect everyone.
The nerve system has a direct effect on the immune system due to the nerve supply to the important immune system organs including: the spleen, lymph nodes, thymus, and lymphoid cells. The many different cells, organs, and tissues that make up the immune system are dispersed throughout the body, yet the various components communicate and collaborate to produce an effective response to an infection over the nerve system.
Your central nerve system is comprised of your brain, brain stem, spinal cord and nerve roots. The skull protects the brain. The brain stem, spinal cord and nerve roots are housed in and protected by the spine which is made up of individual, movable vertebra. If the vertebrae of the spine are not properly aligned, the brain stem, spinal cord or nerve roots can become compressed or irritated by the very bones designed to house and protect them. This is called a subluxation. The chiropractor’s primary role is to detect and correct this problem. Chiropractic is the only health discipline focused on the maintenance of this critical linkage between the nerve system and the immune system.
Reference: yourspine.com