Arrange in order of action.
(i) Activation of helper T cells
(ii) Release of cytokines
(iii) Activation of killer T cells
(iv) Release of perforins
(v) Bursting of infected cells
i, ii, iii, iv, v
Macrophages engulf viral particles and display the viral peptides on their cell surface. The helper T cell binds to the macrophage, and gets activated or is “switched on”. Upon activation, the helper T cells divide and release chemicals called cytokines. Cytokines activate killer T cells to attack. Killer T cells release special enzymes called perforins, which bore channels through the infected cell membranes. This allows water to rush in, causing these cells to swell, break apart and die.