Answer
Activated T cells differentiate initially into effector cells and into memory. The three main types of effector T cells are T-helper cells (T-H cells), T-cytotoxic cells (T-C cells) and T-regulatory cells (T-reg. cells).
1. Helper T cells activate macrophages and stimulate the differentiation of T-cytotoxic cells.
Macrophages act directly and through the agency of cytokines.
2. Cytotoxic T cells (Tc cells) are effector CD8 cells. Once activated they function in the following
ways:
They kill virus-invaded body cells.
They kill cancer cells
They police graft versus host reactions
3. T- Reg cell inhibit or stop immune activity. They are of particular importance in preventing the
development of auto immune diseases
Work Step by Step
T-cells are very important in inducing vigorous, protective cellular immunity. T-cell independent immunity is tepid. The stimulation of CD8 cells by T-H cells results in the transformation of CD8 cells into T cytotoxic cells. T-H cells attract macrophages into an inflammatory situation and make them more powerful killers.
The most important T-H subsets are TH-1, TH-2, and TH -17: TH-1 stimulates macrophages and promotes the differentiation of T-Cyt cells; TH-2 cells provide important defense in allergic and parasitic diseases. They are able to mobilize eosinophils as defensive cells in these conditions; TH-17 cells oppose extracellular pathogens, promote inflammation, and help in combating autoimmune reactions
T-Cytotoxic cells kill other cells directly, and activate CD8 cell to do so. Cytotoxic T cells ( and NK cells) are the two important arms of immune surveillance. They travel through the body seeking virus-infected cells; they also hunt down bacteria. parasites, cancer cells and transplanted cells. T-cytotoxic cells destroy offending cells through the production of perforins and granzymes. They also direct unwelcome cells to die by apoptosis. NK cells are able to detect foreign cells that elude T-C cells
T-regulatory cells (Treg. cells) act to inhibit or stop undesirable immune responses like those of autoimmunity. T-reg cells are also called T-suppressor cells They suppress the responses of lymphocytes in the periphery of the body--that is outside the lymphoid organs-- and promote tolerance to self antigens.
Some examples of autoimmune diseases are Addison's disease, pernicious anemia, glomerulonephritis, and rheumatoid arthritis.
