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In this activity the focus is the investigation of the specialized cells of the immune system that protect the body from pathogen invasion. The immune system is a specialized system made up of billions of cells the bulk being lymphocytes (WBC). The body has specific and non specific defenses that enhance each other’s effectiveness. This activity deals specifically with the many roles a T-cell (type of lymphocyte) has during pathogenic invasion. This lymphocyte is different from other lymphocytes in that it has receptors on their cell surface called T-cell receptor (TCR). The abbreviation T, in T-cell, stands for thymus where these cells mature. T-cells produce a substance that stimulates an immune response called cytokines. T-cells are like soldiers looking for and destroying body invaders. A pathogen in the body is met by a macrophage who engulfs it and displays pieces of the bacterium on the surface which are called antigens. These antigens activate special T-cells called helper T-cells which quickly divide and send messages to another kind of T-cell known as killer T-cells. These killer T-cells recognize an infected cell and kill them. Helper T-cells also activate B-cells that produce antibodies to kill the pathogen. The antibodies cling to the surface of the bacterium, a special protein joins it and together they make holes in the cell and destroy the infected cell. Cytotoxic T-cells destroy viral infected cells and tumor cells. Memory T-cells retain the antigen affinity in case of re-infection. Suppressor T-cells shut down T-cells toward the end of an immune reaction.
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