Well, one immigrant gave me half my DNA. My dad came to the UK from "the continent" at the end of Second World War and met my mum – and here I am.
My parents were told by the teachers that I was not quite good enough to get into Grammar School. I would not pass the Eleven-Plus which was the exam which determined, in the UK, in those times, whether you went to a "good" school (Grammar School) or not. (Why someone's fate should be decided at 11 years old I cannot tell you.)
Anyway, when my parents (one native English and one a refugee immigrant), heard this, they sent me to a maths teacher to learn how to pass the IQ tests. And this maths teacher was a Polish immigrant. He taught me how to pass the 11+. This immigrant taught me how to pass an IQ test. And I did.
So, one immigrant gave me half my DNA, and another got me into a good school.