T- Lymphocytes play a major role in destruction of the tumor cells. T-cell activation includes the production and activation of TH, TD and TC cells. Lymphokines released by the activated T-cells trigger and mobilize B-cells.

The triggered B-cells produce plasma cells to secrete Abs against the tumor Ags (Refer antigens) developed on the newly formed tumor cells. Immune system engages all kinds of immune reactions such as cell mediated immune reactions, Ab dependent reactions, complement mediated reactions, phagocytization etc. to get rid of the tumor cells. Lymphokines such as B-cell growth factors, B-cell differential factors, migration inhibition factors etc. play an important role in immune surveillance of tumor cells.

Sufficient quantities of IL-2 produced by Ag stimulated T-lymphocytes must be present in order to mount an effective counter attack against the tumor ell population.