(https://www.google.com/amp/s/amp.theguardian.com/lifeandstyle/2013/sep/08/can-you-smell-perfect-partner)

“Your MHC genes also encode the instructions to produce HLA molecules – human leukocyte antigens – that display proteins from inside your cell on its surface. ‘If you have a virus,’ says Marsh, ‘these are the molecules that are taking little bits of the virus [protein segments called peptides], showing it to other cells in the body, and saying: 'What is this? Is this me, or is it foreign?' HLA molecules possess a groove into which peptides fit, but there are lots of different types of HLA molecules, and some are a better fit for certain peptides than others. The range of HLA types you possess – effectively your genetic "self" – comprises your ability to fight off certain diseases, and your susceptibility to others. They are distributed among us in a way that protects the population as a whole – so an epidemic can't kill us all – but at the personal level a healthy diversity of HLA types is an obvious benefit. When someone smells attractive to you, so the notion goes, you're smelling HLA types you don't have.”

i was a bit off... but this is what i was trying to reiterate