What is immunity ? Give an account of cell-mediated immunity.

Explanation

Immunity is the capacity of an organism to resist or defend itselff against the development of a disease.
It has two main types i.e., innate immunity and acquired immunity . Immune response is the specific reactivity induced in a host by an antigenic stimulus. The immune response is of following types
1. Humoral or Antibody Mediated Immunity (AMI)
2. Cell-Mediated Immunity (CMI) Cell-mediated immunity is the responsibility of a sub group of T-cells, called T-cytotoxic cells. An activated T-cytotoxic cell is specific to a target cell which has been infected and kills the target cell by a variety of mechanisms. It prevents the completion of life cycle of the pathogen, since it depends on an intact host cell. Cell-mediated immunity is also involved in killing of cancer cells. T-cells attack the following
(i) Cells that have become infected by a microorganism, most commonly a virus.
(ii) Transplanted organs and tissues.
(iii) Cancer causing cells.
The whole cell is involved in the attack, so this type of immunity is described as cell-mediated immunity.T-cells do not release antibodies: