How blood and immune systems form in developing bone marrow
Researchers have found that in the space of just a few weeks, numerous blood and immune cell types emerge from developing bone marrow, including key white blood cells that protect against bacteria.
Professor Muzlifah Haniffa, lead for the Newcastle BRC’s Skin and Oral Disease theme, was part of the first comprehensive analysis of how the blood and immune systems develop in prenatal bone marrow. Other collaborators are fellow scientists at Newcastle University, including Thomas Creasy, a haematology doctor and current trainee with Newcastle BRC, and the Wellcome Sanger Institute.
The study, published in Nature, is part of the Human Cell Atlas (HCA) initiative to map every cell type in the human body, to transform our understanding of health, infection and disease. This study will be an important reference for understanding how the blood and immune systems develop in bone marrow, and how this can go wrong in disorders such as leukaemia, with important implications for diagnoses and treatments.
A previous HCA study described how the human blood and immune systems begin to develop in the yolk sac and liver, a process known as haematopoiesis. But until now, it was unknown how haematopoiesis continued in bone marrow, which produces blood and immune cells for the rest of the individual’s life.
Although the human blood and immune system generally protects us from infection and disease, the system can go wrong and lead to immune deficiencies and cancers such as leukaemia, a cancer that affects white blood cells.
The team observed the rapid diversification of blood and immune cells into specialist types, including white blood cells called neutrophils that protect against bacteria. This diversification occurred over six to seven weeks early in the second trimester of pregnancy. Compared to fetal liver, there were a large number of B-lymphoid cell types, which are needed both to help combat infection and to mount an effective response to vaccines.
Professor Muzlifah Haniffa was a senior author of the paper. She said:
However much we may have thought that we understood the immune system, it is actually far more complex than we had realised. Data like this provides the resolution needed to properly understand what is happening at a molecular level during development.
Reference: Laura Jardine and Simone Webb et al. (2021) Blood and immune development in human fetal bone marrow and Down syndrome. Nature. DOI: https://doi.org/10.1038/s41586-021-03929-x
Story adapted with thanks from Newcastle University Press Office, see the original here