Science goes one step further to find out which cells make up the human body. Several international research groups have created a freely accessible atlas of the cells that make up the immune system through the international consortium Human Cell Atlas (HCA, for your follow in English). Until now, this type of cell had been little explored compared to those that circulate in the blood, such as white or red blood cells. In total, detailed maps of more than a million cells in 33 organs have been published.
This is the result of two studies published in Science and led by the Wellcome Sanger Institute and the University of Cambridge, in the United Kingdom. The ultimate goal is to map all cell types in the human body to understand human health and to diagnose, monitor and treat disease.
The first of the investigations focuses on the early development of the immune system and the location of the cells that compose it. The second has studied immune cells in different tissues of adults. Knowing the reactions of this type of cells in tissues, at different stages of life, could contribute to improving therapies aimed at improving the immune response to fight diseases, such as vaccines or cancer treatments.
In addition, the journal Science echoes two other investigations that have created cross-sectional cell atlases of complete and freely accessible tissues, which will also contribute to the creation of a single Human Cell Atlas.
The complexity of the immune system
The human immune system is made up of many different types of cells that are found throughout the body and that perform crucial functions. They not only fight pathogens when they appear, but remember them so they can be eliminated in the future.
The Wellcome Sanger Institute and its collaborators have created an atlas of the developing human immune system across nine organs. To do this, they have used spatial transcriptomics to understand the cellular diversity of tissues, and single-cell RNA sequencing to map the exact location of specific cells within developing tissues.
Scientists have identified a new type of distinctive B and T cells that appear early in life. The team used data from the other Human Cell Atlas study to show that these particular immune cells are not found in adults.
Muzlifah Hannifa, from Wellcome Sanger and the University of Newcastle, and one of the lead authors of the first paper, explains: “This comprehensive atlas of human immune development reveals the tissues involved in blood and immune cell formation, which improves immune function. our understanding of immune and blood disorders. In collaboration with the other studies, it makes it possible to map the immune system from development to adulthood.”
A Cellular Catalog of the Adult Human Body
In the second study, scientists at Wellcome Sanger, the University of Cambridge and other centers simultaneously analyzed immune cells from 16 tissues from 12 adult organ donors. The team also developed a database and an algorithm that automatically classifies different types of cells, called CellTypist, to handle the large volume and variation of immune cells. In this way, they have managed to identify about 100 different cell types.
In this way, they have revealed the relationship between the immune cells of one tissue and their homologues in others, until finding similarities between certain families of immune cells, such as macrophages, as well as differences in others. For example, some memory T cells display unique characteristics depending on the tissue in which they are found.
“We have created a catalog of immune cells within the adult human body, allowing us to automatically identify cell types in multiple tissues. We want to thank the donors and their families who have made this research possible”, says Cecilia Domínguez Conde, co-author of the second study at Wellcome Sanger.
For Joanne Jones, also a co-author from the University of Cambridge: “In this research we have not only identified different types of immune cells, but we have also discovered that some types of immune cells follow specific distribution patterns in tissues. This may help inform research into disease and how treatments targeting these cells might affect other tissues."
"In addition to creating a new resource for researchers to classify different cell types, our work will have many translational implications, such as providing a framework for developing therapies to fight immune-related diseases and manage infections," concludes Sarah Teichmann, co-lead author of both studies.