S'pore scientists discover origin to long-lived, skin-deep immune cells

SINGAPORE - Singapore scientists have discovered the origin of a group of skin-deep immune cells that act as the first line of defence against harmful germs and skin infections.

A*STAR's Singapore Immunology Network (SIgN) scientists found that these sentry cells of the skin, called the Langerhans cells (LCs), originate from two distinct embryonic sites - the early yolk sac and the foetal liver.

The first wave of precursor cells come from the yolk sac 'seed' the skin before the onset of the foetal liver. In the later stage of development, the yolk-sac precursors are largely replaced by a type of white blood cells from the foetal liver.

LCs are dendritic cells (DCs) found in the outermost layer of the skin.

DCs are a critical component of the immune system because they are the only cells able to 'see' and 'alert' other responding immune cells to initiate a response against foreign invaders.

Identifying the source of these specialised immune cells opens the way to developing strategies for vaccination and treatment of autoimmune diseases and inflammatory skin disorders, said Dr Florent Ginhoux, Principal Investigator of SIgN.

In contrast to other DCs which are constantly replaced by a circulating pool of bone marrow-derived precursors, LCs have the ability to maintain themselves throughout life.

While it is established that these long-lived sentry cells of the skin arise from precursors that are recruited to the skin prior to birth, this is the first time that the exact origin of the precursors of LCs is revealed through advanced fate-mapping technique - a method of tracing cell lineages to their embryonic origin.