When cytokine secretion ceases, the lymphocytes undergo apoptosis. There are two ways by which a cell dies. Most damage is in the plasma membrane, leading to the loss of the cell's ability to regulate osmotic pressure, resulting in rupture of the cell and spilling of its contents in surrounding tissue. This triggers an inflammatory response. Unlike what happens in necrosis, this immediate phagocytosis permits no spilling of the cellular contents and prevents the development of inflammation.
Apoptosis is an active process and involves the induction of several molecules and pathways.
Two pathways involved in apoptosis illustrate the possible diseases that can result from abnormal apoptosis. An enzyme called Bcl-2 can inhibit apoptosis. A molecule-ligand interaction on the cell surface is also involved in apoptosis. Cross-linking of Fas activates the apoptosis pathway. The absence of Fas or Fas-ligand can theoretically lead to the persistence of lymphocytes and to massive lymphadenopathy.