PATHOLOGY

Detailed explanation-1: -Cytotoxic CD8 T cells carry out their killing function by releasing two types of preformed cytotoxic protein: the granzymes, which seem able to induce apoptosis in any type of target cell, and the pore-forming protein perforin, which punches holes in the target-cell membrane through which the granzymes can enter.

Detailed explanation-2: -Natural killer (NK) cells and CD8-positive T-cells are the main source of perforin. However, CD4-positive T-cells are also able to express a low amount of perforin, when classic cytotoxicity is ineffective or disturbed.

Detailed explanation-3: -Helper T cells secrete cytokines that help B cells differentiate into plasma cells. These cells also help to activate cytotoxic T cells and macrophages. Regulatory T cells (or Tregs) help to suppress the immune system. Lymphocytes are immune cells found in the blood and lymph tissue.