The Spleen Immune System


How much do you know about your spleen? If you’re anything like a lot of people, your answer to that question may well be, not very much. A lot of us aren’t even aware of what the spleen’s broader purpose is, or where it is in the body, let alone what it might do to strengthen the immune system.

So, let’s clear up some of those mysteries. And if you know little about the spleen other than the popular phrase, “venting one’s spleen” – no, this organ has nothing to do with expressing frustration.

That particular phrase can be traced back to medieval times, when it was genuinely believed that the spleen was the source of anger. However, as scientists throughout subsequent centuries have discovered, the spleen actually exists for very different reasons.

What is the spleen, and what does it do?

The spleen is a soft organ located in the upper left part of your abdomen – protected by your ribcage and just behind your stomach, but under your diaphragm. Its size and weight can greatly vary from one person to the next, but in healthy individuals, it tends to be about three to 5.5 inches long, and between five and seven ounces in weight.

What, then, is the spleen for? A good way to think of the spleen, is as a filter for your blood. This is the main purpose of this highly vascular organ, which acts as a sort of “quality control” department for the blood that flows through it.

The red blood cells that pass into the spleen and are discerned to be healthy are allowed to continue circulating through the rest of the body. Meanwhile, blood cells that don’t satisfy the spleen’s scrutiny – due to being old, damaged or malformed – are removed and broken down. Large white blood cells called macrophages have the job of destroying such red blood cells that are no longer fit for purpose.

An organ that impacts your immunity more than you might think

Not everything that the spleen does has an obvious connection to the immune system. One of its jobs, for example, is to store reserve blood, which can then be released if your body requires it in any circumstance that might cause blood loss, such as a traumatic injury.

But with the spleen being the largest organ in the lymphatic system – the network of tissues and organs instrumental in the body’s routine removal of waste, toxins and other unwanted materials – it definitely has an important part to play in supporting immunity.

Going back to our earlier point about how the spleen assesses the condition of your red blood cells, it can also detect unwelcome invaders in your blood, such as viruses and bacteria. When the body does identify these undesirable micro-organisms in your bloodstream, your spleen and lymph nodes respond by producing defender cells known as lymphocytes.

Lymphocytes are white blood cells that create antibodies – special proteins capable of destroying or weakening viruses, bacteria and other organisms that can lead to infection. Even when white blood

cells and antibodies do not kill germs, they help to trap them to slow down the spread of infections throughout the rest of the body.

But isn’t it possible for the body to survive without a spleen?

This is absolutely true – while the spleen is definitely an important one for reasons like those outlined above, it isn’t strictly essential. Some people may have their spleen surgically removed due to damage caused by disease or injury, and can live normal and healthy lives after this procedure. Indeed, other areas of the body, such as the liver and lymph nodes, are capable of assuming a lot of the spleen’s functions in these individuals. Such is the importance of the spleen to immunity, however, that people are more vulnerable to certain infections after their spleen is removed. Depending on their all-round health and age, they may therefore be advised by medical professionals to get vaccinated against risks like the flu, meningitis and pneumonia.

The spleen, then, plays a vital role in your body’s immune response, although it’s far from the only factor that will influence your ability to fend off those nasties. Ensuring you get the important minerals and vitamins for immunity – including through your diet – will also always be imperative, if you are to minimise your susceptibility to infectious disease and maintain optimum health.

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