How our immune cells are born

Scientists have now discovered the origin of immune cells (our body's defence mechanism). 'Follicular dendritic cells' (FDCs) are not blood cells, and their origin has been a mystery until now. They play a critical role in allowing us to fight infections and create a strong armory 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.

As earlier perceived, many of our immune cells arise out of bone marrow, but FDC's arise from 'mural cells' that surround blood vessels. FDC's are observed in tonsils, spleen and lymph nodes where they are formed during embryonic development and soon after birth. Since FDC's have been found at the site of chronic inflammation in response to immune system failure , illness or injury, they have been linked to our immune system.

This finding 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. 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.

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 is) localised powerhouses of antibody generation. 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.

Source: IANS