Sperms, immune system

Why does the immune system in females not attack sperms (foreign bodies) that enter the female body?

R. SUJITHA

Chennai

The basic tenet of the human immune system is that it can differentiate ‘self’ from ‘others.’ This allows the body to fight off any foreign cells which it encounters. That is why it is difficult to transplant organs without suppressing the immune system.

However, when it comes to reproduction, the human body not only ignores the sperm, but also fails to recognise the foetus (which has half of its material from a ‘foreign’ donor) as a foreign body. In the decidua — the tissue surrounding the foetus and the placenta — the immune response is switched off and thus preventing an assault on the developing baby.

It is obviously an evolutionary advantage for the female body not to recognise sperms as dangerous foreign invaders. Studies have confirmed the presence of markers on the surface of the human sperm that prevent them being attacked by the female immune system. These markers on the sperm are universally recognised by any woman’s immune system, and trick the immune system into believing that the sperm is harmless. That is why reproduction can occur between any two people.

However, there are probably many still unrecognised mechanisms which allow sperm to escape the ‘search and destroy’ mission of the female immune response.

Dr GITA ARJUN

E V Kalyani Medical Centre

Keywords: immune system