Leading researcher, Robert Lisak, M.D., a professor of neurology at Wayne State explained that B cells belong to a subset of circulating white blood cells (lymphocytes), which become immunoglobulin (antibodies) producing plasma cells when mature. However, B cells also seem to play a role in controlling other lymphocytes, particularly T cells, and help to regulate a healthy immune system.
The B cells attack the brain and spinal cord in patients with MS, which could be due to the fact that the nervous system and the meninges, the covering of the brain and spinal cord, produce substances that attract the B cells. Once within the meninges or central nervous system, the activated B cells secrete one or several substances that damage oligodendrocytes, i.e. cells that produce myelin, a protective substance, yet which do not seem to affect the immunoglobulins. The scientists observed that B cells seem to be more active in MS patients. This may explain whey these cells produce toxic substances and partially why they are attracted by the nervous system and the meninges.
Most of the brain is split into gray areas that contain neurons, and white areas, where neurons send their axons just like electrical cables carry messages, in order to communicate with other neurons and transfer messages from the brain to the muscles. The white parts of the brain have their particular color because the oligodendrocytes produce myelin, the axons' coating/insulation similar to that to the plastic coating of electrical cables, which is rich in cholesterol. Myelin accelerates communication along the axons, making it more reliable, yet when this coating degrades or is attacked, it can lead to 'leakages' or messages being sent to the wrong receptor during communication from the brain to other body parts. The team noted that oligodendrocytes also appear to play a role in other activities, which are vital for the nerve cells and their axons.
For their study, the team obtained B cells from the blood of 7 MS patients that had relapsed or were in remittance and from 4 healthy patients. The researchers grew the cells in a medium and collected the material the cells produced after removing them from the culture.
They grew the cells in a medium, and after removing them from the culture they collected the material the cells produced and implanted it together with the cells that produce myelin into the brain cells of animal models. They discovered that considerably more oligodendrocytes died within the MS group compared with the material produced by the B cells from the healthy patients. In addition, they also observed differences in other brain cells that interact with oligodendrocytes in the brain.
"We think this is a very significant finding, particularly for the damage to the cerebral cortex seen in patients with MS, because those areas seem to be damaged by material spreading into the brain from the meninges, which are rich in B cells adjacent to the areas of brain damage."
The team is planning to continue their studies to find which B cells' toxic factor(s) is/are responsible for destroying oligodendrocytes, as this could potentially lead to new treatments that could switch off the oligodendrocyte-killing capabilities of B cells and therefore help to protect myelin.
Written by Petra Rattue