The thymus gland. Prevent disease improve life and longevity

I saw a statistic on a web feed showing reasons for death. Most things on the list can be linked to infections and disease. So could the ability to fight disease determine life length and quality?

Should we focus on improving natural immunisation and use the thymus properly while young. Or consider  keeping the thymus large by training it.

Taking this further I just saw an article linking the thymus with the idea that well-trained immune cells keep HIV in check.