Opposites Attract to Repel Germs

When it comes to mating, it turns out that opposites really do attract--genetically--according to a recent study at the University of Parana in Brazil.

The study, presented at the European Society of Human Genetics in Vienna last week, showed that among 90 married couples and 152 randomly generated couples, those who were married were more likely to have differences in an immune system molecule, called the MHC, or Major Histocompatibility Complex.

MHC is a protein complex found on the surface of certain cells, called antigen-presenting cells, whose job is to announce the presence of foreign invaders, such as viruses or bacteria. Simply said, when a microbe invades the body, certain white blood cells can break them down and present various parts ("antigens") of the microbe within the MHC on the surface of the cell. When another type of white blood cell, called a T cell, recognizes that there's something foreign sticking out of the antigen-presenting cell, it can trigger a cascade of events leading to destruction of that microbe.

So why would people with different MHCs attract? Different types of MHCs present different parts of a microbe, thus playing a distinct role in how strong a person's immunity is. For example, a person who has very diverse MHCs will be able to trigger a more thorough immune response, compared to someone whose immunity is limited due to low MHC diversity.

Apparently, people with dissimilar MHCs attract for the sake of their offspring, who end up carrying a greater diversity of MHCs.

Interesting. What ever happened to good ol' physical attraction?