A group of scientists managed to count (and weigh) immune cells. Discovering that…
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We imagine it as something impalpable that wanders in our body to protect it from external aggressions. Actually, the immune system is a network of 1.8 trillion cells, tissues and organs, concrete and with a well-defined weight. And it is precisely on the mystery of its dimensions that a study published a few days ago focused…
How much does the immune system weigh?
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According to a group of researchers at the Weizmann Institute of Science in Israelled by biologist Ron Sender, in a healthy adult male of about 73 kg, between 20 and 30 years old, the immune system is approximately equivalent to 1.2 kg, as much as a medium-large pineapple. While an adult woman of the same age weighing 60 kilograms would likely have around 1.5 trillion immune cells, for a total of 1 kilogram. The researchers arrived at these estimates by counting the total number of immune cells in the body and analyzing their distribution in various organs. The burden of the immune system may vary based on factors such as age, gender and health status and knowing its actual dimensions helps us better understand how it works. “Despite many studies investigating the human immune system from different angles, a comprehensive census of the distribution and mass of various types of immune cells was needed,” explain the study authors.
Where is the immune system hiding?
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But where exactly are all the cells that make up the immune system located? According to Sender, most of them are in the lymph nodes distributed throughout the body, in the lymphatic organs and in the lymphoid tissue associated with the intestine. The researchers estimated that B and T lymphocytes, which produce antibodies and directly fight foreign agents, make up about 40% of total immune cells. However, being very small, they correspond to only 15% of the total mass. Neutrophils, which engulf the bacteria, make up another 40% of the cells and 15% of the mass. Finally, although present in smaller percentages, macrophages and other large cells contribute over 60% of the total weight of the immune army.
But the surprise is another: the intestine, traditionally considered the main seat of the immune system, actually hosts only 3% of total immune cells. Even less, 2%, is found in the blood. The main “barracks” organs of the immune troops are the lymph nodes, the bone marrow and the spleen: here resides the majority of lymphocytes and neutrophils. However, the intestine contains the highest proportion of plasma cells, responsible for the production of antibodies. Therefore, more than in numerical terms, it contributes crucially to ours immunity. Further confirmation that the health of the intestine reflects that of the entire organism.
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