The various white blood cells, as well as the red blood cells and the blood platelets, develop from blood stem cells in the bone marrow, orchestrated by different molecular switches called transcription factors. They tell the cells which direction "to go". Until now, it has been assumed that once human blood cells have developed into one direction they are no longer able to leave their path. However, experiments in mice have shown that mature B lymphocyte cells have the ability to do exactly this: reprogramming and developing into different cell lineages. Until now, it was unclear whether human blood cells can undergo similar processes.
Now, Drs. Mathas and Janz at the Max Delbruck Center for Molecular Medicine (MDC) Berlin-Buch (Germany) and the Charite University Medicine Berlin (Campus Virchow and Campus Buch), publishing in
Nature Immunology (doi:10.1038/ni1285, 2005), were able to show that in Hodgkin Reed Sternberg cells, which originate from B cells, the program which steers the differentiation of B cells is defective. One of the central regulators of B cell development, called E2A, is blocked by two antagonists, known as Id2 and ABF-1. Following inhibition of E2A, B cell characteristics are lost and genes for markers of other immune cells, such as macrophages and T cells, which are not characteristic for B cells, are upregulated. Thus, the B cells have changed their appearance. These findings shed light on the extraordinary appearance of Hodgkin Reed Sternberg lymphoma cells.
