London, February 7 : A study of mouse lymph nodes, bean-shaped organs that contain a variety of immune cells and are distributed throughout the body, has shown that immune cells confront viruses just inside of the lymph node and not deep within these organs, as previously thought.
The findings of scientists from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), may help improve the understanding as to how the immune system operates during a viral infection, which is critical to designing successful anti-virus vaccines.
Chief of the NIAID Cellular Biology Section Dr. Jonathan Yewdell and his colleague Heather Hickman say that their findings are significant as they are based on a detailed interaction of viruses and immune cells inside a living organism.
During the study, the researchers extracted and purified specific T cells from mice. The T cells, which attack and kill infected or cancerous cells, were then marked with a fluorescent marker and injected back into the mice.
The scientists later infected the animals with vaccinia virus, the virus used to make smallpox vaccine. The virus was engineered to express a brilliantly coloured protein.
With the help of a highly specialized multiphoton microscope, the scientists looked into the lymph nodes of the infected mice. They saw that the viruses had infected cells just inside the lymph node surface, triggering a swarm of T cells.
The researchers say that the virus-specific T cells form an elaborate and dynamic communications network that activates them to divide and travel to the site of viral infection, where they kill virus-infected cells.
"A key challenge in viral vaccine research is developing strategies for immunizing against lethal viruses such as HIV that have eluded the standard vaccine approaches," Nature Immunology quoted Dr. Yewdell as saying.
"We have contributed a page to the handbook of understanding how to rationally design vaccines to elicit a T-cell response," Dr. Yewdell added.
The NIAID team says that pinpointing where in the lymph node immune cells fight the virus should help efforts to design effective anti-virus vaccines.