Medical Health Encyclopedia

T cells are further categorized as killer T cells or helper T cells (TH cells).

• Killer T cells directly attack antigens found on bacteria or other cells.
• Helper T cells also recognize antigens, but their role is two fold. They stimulate B cells and other white cells to attack the antigen. They also produce cytokines, powerful immune factors that have an important role in the inflammatory process.

Helper T cells, Cytokines, and the Inflammatory Response. The actions of the helper T cells (TH cells) are of special interest. Researchers have observed high numbers of TH cells in psoriatic plaques:

• The activated TH cells infiltrate the skin cells in psoriasis and, in the case of psoriatic arthritis, also the joints. (There has been some debate over whether psoriatic arthritis is a unique disorder, but evidence now suggests that both psoriatic arthritis and psoriasis are caused by the same faulty immune process.)
• TH cells normally stimulate B cells to produce antibodies. In the case of psoriasis, however, they appear to direct the B cells to produce autoantibodies ("self" antibodies), which are directed against the body's own cells. In the case of psoriasis, they target self antigens in skin cells; in psoriatic arthritis, cells in the joints also come under attack.
• In the resulting autoimmune process, autoantibodies remain in circulation and continue to mount an immune attack against these cells.

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Helper-T cells and Cytokines. TH cells also secrete or stimulate the production of powerful immune factors called cytokines. In small amounts, cytokines are indispensable for healing. If overproduced, however, they can cause serious damage, including inflammation and injury during the psoriasis disease process. In psoriasis, researchers are particularly interested in cytokines known as GRO-alpha, tumor necrosis factor, and certain interleukins.