It has been suggested that MHC plays a role in the selection of potential mates, via olfaction. MHC genes make molecules that enable the immune system to recognise invaders; generally, the more diverse the MHC genes of the parents, the stronger the immune system of the offspring.
In the context of mate selection, MHC may use olfaction to choose partners with diverse immune systems, which can lead to stronger immunity in their offspring. This is analogous to how genetic variation in the parents' immune molecules influences the robustness of their offspring's immune systems.