Final answer:
The statement is false; cytotoxic T cells are CD8+ T cells, not CD4 cells. CD4+ cells are Helper T cells, which assist the immune response by releasing cytokines and activating other cells, while CD8+ cytotoxic T cells are responsible for directly killing infected cells.
Step-by-step explanation:
The statement "Cytotoxic T cells are also called CD4 cells" is false. Cytotoxic T cells, which are crucial components of the adaptive immune system, are actually characterized as CD8+ T cells. These cells are specifically designed to attack and destroy infected cells, a key defense against viral infections as viruses reproduce within the cells, making them inaccessible to antibodies. Once activated, cytotoxic T cells can induce apoptosis in infected cells using mechanisms like the one used by Natural Killer (NK) cells, which includes the use of Fas ligand or perforins and granzymes.
On the other hand, CD4+ T cells are commonly referred to as Helper T cells and serve a different function. They become activated when they engage with MHC II molecules on antigen-presenting cells (APCs). After activation, they can stimulate other immune cells, such as B cells and CD8+ T cells, the latter of which differentiate into cytotoxic T cells. Contrary to cytotoxic T cells, Helper T cells aid in coordinating the immune response by releasing cytokines rather than directly killing infected cells.