From The MS Information Sourcebook, produced by the National MS Society.
Immune function is helped by two kinds of white blood cells. The "B cells" (so-called because they develop in bone marrow) produce antibodies. The "T cells" (so-called because they develop in a small organ called the thymus gland) are responsible for a variety of other immune responses. These responses include: 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.
Three Broad Categories of T cells
Individual T cells are able to recognize only certain antigens. Their ability to discriminate between antigens is conferred by protein molecules on the cell surface called receptors. The receptor and the antigen fit together like a lock and a key only when their shapes match perfectly. The number and specificity of T-cell receptors appears to be determined by the cell's genes.
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 some component of central nervous system myelin (the fatty sheath that surrounds and insulates nerve fibers). Demyelination—the destruction of myelin—causes nerve impulses to be slowed or halted and produces the symptoms of MS.
Much More Now Known about Roles of T Cells
Therapies Directed Against Specific T cells or T-cell Receptors
While much more information is needed before the exact nature of the autoimmune response in MS is explained, it appears that T cells and their cytokines are the keys to this process. Ongoing research in these areas may provide new, specific immunotherapies that will stop the progression of MS, without harming any immune cells that are not involved in the process of myelin destruction.
Kalb R. (ed.) Multiple Sclerosis: The Questions You Have; The Answers You Need (3rd ed.). New York: Demos Medical Publishing, 2004.
Last updated October 2005