Although the entire body works together in unison, the immune system, overall, is especially difficult to describe in a nutshell. Immune cells are found all throughout the body and, more than perhaps any other system, it is integrated into all the others. There aren’t a lot of structures that “stand alone.”
White blood cells, as the name implies, are a component of blood — but they’re part of the immune system.
Immune cells are initially created in the bone marrow — so closely tied to the skeletal system.
The tonsils and adenoids (in what most people would consider part of the respiratory system) and the appendix (within the digestive system) are all immune-related tissues.
Gut bacteria play a significant role in modulating the immune response.
The only really “freestanding” elements of the immune system are the lymphatic circulation, thymus, and spleen.
The thymus gland is located behind the breastbone. Early in life, it’s responsible for the development of T-cells, one type of immune cells. It is also believed to play a role in helping the body avoid autoimmunity. After puberty, this gland begins to atrophy, replaced gradually by fat. Some of its tasks are taken over by other parts of the immune system, while other tasks are no longer needed.
The lymphatic system, as a whole, vaguely resembles the circulatory system. It is comprised of lymph nodes and lymph vessels. The lymph vessels, as might be expected, carry lymph. Lymph is a whitish fluid comprised mostly of fluid pulled from the “intracellular” space — the space between cells. Lymph vessels take this fluid in and circulate it through lymph nodes where it is filtered. The lymph nodes hold a complement of immune cells which, between them, “eat up” certain unwanted material and respond to pathogens (the “bad guys”).
Unlike the circulatory system, the lymphatic circulation has no pump, so it’s heavily reliant on the movement of surrounding tissues to keep it moving effectively. This is one reason regular movement/exercise is important. It’s also one way massage can be beneficial.
The final major organ in this system is the spleen. Like the lymph nodes, the spleen also serves as a locus for eating up waste material and responding to pathogens. It also helps break down and recycle certain blood cells, and to manufacture immune cells. (Somewhat unrelated to the immune system, the spleen also stores a sort of “emergency supply” of blood. The body can draw on this as a short-term means of helping maintain blood pressure in the case of some internal injuries.)
Healthy Immune Function
‘Most everyone knows that being “sick all the time” is generally the sign of a not-so-healthy immune system. (If it’s simply a matter of recurring illness over a brief period of time, the immune system might be more depleted than dysfunctional and just need a bit of support to get back to normal.) What you might not know is that never being sick may also indicate a weakness in the immune system. We want illness to be rare and brief, but if it’s been several years and you haven’t had so much as a cold, that may be an indication that your immune system isn’t functioning optimally (if, for instance, it’s too weak to respond to stimuli).
Allergies, auto-immune disorders, and the like are signs of a hyperactive immune system. This immune system is constantly on high alert, unable to modulate itself or turn itself back “off” when not needed. Supporting the immune system may provide at least partial relief, if you’re able to restore its ability to keep balanced.
Inflammation of lymphatic tissue is also not normal — but usually not a root problem. For instance, swollen tonsils and adenoids may be a completely normal response to an acute infection. If they remain swollen, or are swollen with no apparent cause, that becomes an issue. However, it’s important to note that this is not a problem with the tonsils and adenoids. A common “treatment” is to remove the offending tissue; the problem is this doesn’t actually “treat” the underlying issue that caused them to become swollen in the first place. (A commonly-overlooked cause is suboptimal oral development.)