The first comprehensive analysis of how the blood and immune systems develop in prenatal bone marrow has been conducted by scientists at the Wellcome Sanger Institute, Newcastle University and their collaborators. The researchers 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.
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 disease1. It 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 leukaemia2.
In this study, researchers from the Wellcome Sanger Institute, Newcastle University, the University of Cambridge and the University of Oxford, used single cell RNA technology to analyse developing bone marrow tissue3 samples, in order to identify the cell types present and which genes those cells expressed.
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.
Source: Sanger Institute