Two specific types of immune system cell that attack invaders - CD4 T-cells and natural killer cells - increased in number with age, with a higher rate of increase in women than in men.

BBC: Biological clue to why women live longer than men

Natural killer cells normally play an important role in inducing apoptosis of cancerous cells and others that have been infected with viruses.

FORBES: Intrepid Investors Eye Use Of Pig Whipworm Eggs To Quell Crohn's Disease and MS