Effect of advanced ageing on the ability of mice to cause tumour regression in response to immunotherapy.

The effect of ageing on tumour immunotherapy was investigated by comparing the ability of aged mice (20 months old) and young mice (3 months old) to cause regression of an established SA1 sarcoma in response to parenteral injection of endotoxin, or to sublethal, whole-body exposure to ionizing radiation. It was found that whereas treatment with either of these agents caused T-cell-dependent regression of the tumour in young mice, it failed to cause regression of the tumour in aged mice. The results are in keeping with extensive literature showing that ageing is associated with a decline in immune competence.