Boosting immune systems

When I asked the GP about the white patches on my hands he said it was vitiligo and it was another auto-immune condition to add to my asthma, eczema, arthritis and hypothyroidism. What I don't understand is whether an auto-immune condition is the same as having a compromised immune system and if so whether I can boost it in any way e.g. by taking zinc?

Any medics who can advise me /explain the differences?

I catch some bugs and avoid others, but I think I'm more resilient when I eat a good, fresh varied diet with lots of vegetables, sleep well and take probiotic and zinc supplements. If I start eating chocolate or takeaway meals and getting lazy about nutrition, I can bet on catching whatever my grandchildren have next.

I wonder too as I have always had a good immune system -or so I thought after years in the classroom. But now whenever one of the little boys so kndly shares the current lurgy I find I am knocked out for a fortnight!! No ill effects though from littlest one's "chicken pops" (sic)

Zinc is the thing.