Cell-Mediated Immune System - Practice Questions & MCQ

• It is the second type of acquired immune system.
• The T-lymphocytes mediate cell-mediated immunity.

Types of T-cells and their Functions:

• Helper T-cells (TH Cells):
  • These are most numerous of the T cells. 
  • They help in the functions of the immune system. 
  • They produce a growth factor that stimulates В-cell proliferation and differentiation and also stimulates antibody production by plasma cells.
  • They enhance activity of cytotoxic T cells.
• Cytotoxic T-cells (TC Cells):
  • These cells are capable of killing microorganisms and even some of the body’s own cells directly hence they are called killer cells. 
  • After binding, the cytotoxic T cell secretes hole-forming proteins, called perforins, that punch large round holes in the membrane of the foreign cell.
  • In addition, the cytotoxic T cell releases cytotoxic substances directly into the foreign cell. 
• Memory T-Cells:
  • These cells are also formed by T-lymphocytes as a result of exposure to antigen and remain in the lymphatic tissue (e.g., spleen, lymph nodes). 
  • They recognize original invading antigens even years after the first encounter. 
  • Suppressor Cells (Regulatory T-cells):
  • These cells are capable of suppressing the functions of cytotoxic and helper T-cells. 
  • They also inhibit the immune system from attacking the body’s own cells. 
• Natural Killer (NK) Cells:
  • NK cells attack and destroy target cells, participate in antibody dependent cell-mediated cytotoxicity. 
  • They can also attack parasites which are much larger than bacteria.