Sydney, Jul 10 (IANS): Scientists have shown for the first time how an important class of immune cells, which spur development of antibodies to fight infections, comes into being.

'Follicular dendritic cells' (FDCs) play a critical role in allowing us to fight infections and create a strong armoury of antibodies for future use. FDCs first make sure that our antibody generating B cells receive samples of an invading organism. They then help to identify and nurture the B cells that manufacture the highest quality antibodies.

Many of our immune cells, including B cells, are white blood cells and so arise out of stem cells in bone marrow. FDCs are not blood cells, and their origin has been a mystery until now, the journal Cell reports.

Scientists have been able to see FDCs in tonsils, spleen and lymph nodes 'where they are formed during embryonic development and soon after birth. They have also seen FDCs at sites of chronic inflammation later in life' such as in a liver inflamed by hepatitis, or in joints inflamed by rheumatoid arthritis. Inflammation is the response of immune system to an illness or injury.

Nike Krautler from Sydney's Garvan Institute of Medical Research and Adriano Aguzzi, professor from the Institute of Neuropathology, University Hospital of Zurich, have now shown that FDCs arise from the 'mural cells' that surround our blood vessels.

"This story was interesting to us because follicular dendritic cells are thought to be stationary cells and can't migrate through our bodies like B cells, which move through the lymph system or blood stream," said Krautler, according to a Garvan Institute statement.

"We could see that they were present in the lymphoid organs, such as the spleen or lymph nodes, right from the start from when the tissue was formed. By using genetic markers we could see that they appeared to come from a particular kind of precursor, or stem cell, that surrounds blood vessels," said Krautler.

"We now believe that during chronic inflammation or autoimmune disease, precursor cells are recruited to the site and form follicular dendritic cells. B cells also migrate there and highly specialised germinal centres form, (which are) localised powerhouses of antibody generation," added Krautler.

"So while this is a basic science finding, it is really central to our understanding of how chronic inflammation is triggered and perhaps in gaining insights about how to prevent them," concluded Krautler.