Bone marrow cells fight viruses.

Evidence is mounting that human bodies produce a class of virus-fighting cells, called T cells, where researchers never expected--in the marrow of bones. Look up these cells in any immunology marrow each day. The function of these T cells is currently unknown. We're just starting to scratch the surface when it comes to understanding the immune system in the bone marrow," notes Samuel Strober, professor of immunology, Stanford University School of Medicine.

The findings could have important implications for those whose thymus glands have been destroyed by the AIDS virus. Researchers have been concerned that, even if the AIDS virus can be stopped, such patients might never regain their T cells because their ruined thymus glands no longer can produce them. The bone...