State immunological surveillance theory.

Explanation

The concept of immunological surveillance postulates that the primary function of the immune system is to"seek and destroy" malignant cells that arise by somatic mutation.The efficiency of the surveillance mechanism reduces either as a result of ageing or due to congenital or acquired immunideficiencies,leads to increased of cancer.Thus,if immunological surveillance is effective ,cancer should not occurs.The development of tumour represents a lapse in surveillance.