The total mass, number, and distribution of immune cells in the human body

Ron Sender, Yarden Weiss, Yoav Navon, Idan Milo, Nofar Azulay, Leeat Keren, Shai Fuchs, Danny Ben-Zvi, Elad Noor, Ron Milo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The immune system is a complex network of cells with critical functions in health and disease. However, a comprehensive census of the cells comprising the immune system is lacking. Here, we estimated the abundance of the primary immune cell types throughout all tissues in the human body. We conducted a literature survey and integrated data from multiplexed imaging and methylome-based deconvolution. We also considered cellular mass to determine the distribution of immune cells in terms of both number and total mass. Our results indicate that the immune system of a reference 73 kg man consists of 1.8 × 1012 cells (95% CI 1.5–2.3 × 1012), weighing 1.2 kg (95% CI 0.8–1.9). Lymphocytes constitute 40% of the total number of immune cells and 15% of the mass and are mainly located in the lymph nodes and spleen. Neutrophils account for similar proportions of both the number and total mass of immune cells, with most neutrophils residing in the bone marrow. Macrophages, present in most tissues, account for 10% of immune cells but contribute nearly 50% of the total cellular mass due to their large size. The quantification of immune cells within the human body presented here can serve to understand the immune function better and facilitate quantitative modeling of this vital system.

Original languageAmerican English
Article numbere2308511120
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number44
StatePublished - 31 Oct 2023

Bibliographical note

Publisher Copyright:
Copyright © 2023 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).


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