The nervous, immune, and endocrine systems share tiny messenger molecules that mediate communication between them. One of these messenger molecules, IL-2, used to be classically thought of as an immune system molecule; however, studies published within the past decade have clearly shown IL-2's presence and activity in the nervous system. One recent pioneering study, "Enhancement of in vitro interleukin-2 production in normal subjects following a single spinal adjustment clearly demonstrated an increase in IL-2 levels and also in the function of T-cells, which are key players in the immune system's army of cells, following chiropractic adjustment. Furthermore, a series of studies published in the Journal of Manipulative and Physiological Therapeutics showed that several types of immune system cells have increased biological activity after chiropractic adjustment. These studies all indicate increased immune system function.
Also, let's not forget that the endocrine system is the third leg in the stool of neuro-endocrine immunology. The endocrine system's main players are adrenaline and nor-adrenaline, and cortisol. These molecules are produced in the adrenal glands, endocrine glands which have direct connections with the nervous system by way of a division called the sympathetic nervous system. Cortisol is a stress hormone that inhibits the immune system (which is why stress really can make you sick!) So if the sympathetic nervous system is too "turned on" due to stress and subluxation, it can increase the adrenal glands' synthesis of cortisol, in turn affecting the immune system.
So Chiropractic really can help by improving the bodies neurological communication, and making our bodies immune system more efficient.