T-Cells

T-cells are a type of white blood cell that play a central role in cell-mediated immunity. Immune function is helped by two kinds of white blood cells: "B-cells" and "T-cells". B cells produce antibodies. T-cells are responsible for a variety of immune responses including: 1) direct attacks on foreign substances such as bacteria, viruses, or foreign tissues; 2) augmenting the B-cell response; and 3) producing substances called cytokines that direct responses and activities in other immune cells.

There are three broad categories of T-cells.

• Helper T-cells augment the immune response by recognizing the presence of a foreign antigen and then stimulating antibody production and producing cytokines that "turn on" or activate other T-cells.
• Suppressor T-cells function in an opposite manner. They dampen or turn off the immune response.
• Cytotoxic or "killer" T-cells directly attack and destroy antigenic material.

It is now generally accepted that the demyelination seen in MS is caused by an abnormal autoimmune process—that is, by activation of T-cells against myelin, the fatty sheath that insulates nerve fibers. Demyelination causes nerve impulses to be slowed or halted and produces the symptoms of MS.

Over the last 15 years, much knowledge has been gained about the specific roles of T-cells. Among the activities that have been observed are:

• Decreased suppressor T-cell function in the peripheral blood of MS patients during an acute exacerbation (also known as an attack, relapse, or flare);
• Increased numbers of helper T-cells in the spinal fluid;
• Increased numbers of activated T-cells passing into the brain from peripheral blood (which then attract other immune cells into the brain);
• Presence of T-cells in MS plaques; and
• Increased frequency of activated T-cells against the myelin seen in MS patients compared to healthy controls.

The abnormal autoimmune process that is responsible for the central nervous system demyelination in MS appears to involve selective activation of helper T-cells and killer T-cells, with a corresponding decrease in suppressor T-cells. These findings suggest the rationale for therapies that target only specific T-cells or T-cell receptors that are sensitized to myelin.

The above information was largely adapted from The MS Information Sourcebook produced by the National MS Society.

T-Cell Vaccine

How does T-cell vaccination work?

According to Dr. Jingwu Zhang, M.D., Ph.D., Director of Research, Baylor Multiple Sclerosis Center, the principle of T-cell vaccination originates from traditional microbial vaccination, like flu shots. In microbial vaccination, viruses and bacteria are de-activated by chemical treatment or irradiation and lose their ability to cause the infectious disease. They can then be used as a vaccine to stimulate the immune system to develop a protective immune response. This immune response is powerful enough to kill the invading viruses or bacteria when the body encounters them during a subsequent infection.

In T-cell vaccination, the myelin-attacking cells are considered pathogens (similar to viruses and bacteria) because of their association with MS. They are isolated from the blood, inactivated by irradiation and injected as a vaccine to sensitize the body's immune system to recognize and ultimately eliminate them from the blood.  

The whole process looks like this:

• Blood is taken from the patient

• Myelin reactive T-Cells are stimulated and isolated from the blood

• Selected T-Cell lines are activated and expanded

• Cultured T-Cells are collected and washed

• T-Cell Vaccine is irradiated to make T-Cells non-replicating

• Portion of final vaccine is tested for quality and sterility

• Final vaccine is injected into patient