Violent Sex Activates Female's Immunity

Biologists thought for long that only vertebrates have complex adaptive immune systems that allow them to fight against many germs after just one infection. But the concept has changed in the last years, as many insects too have been found to have an immune memory that defends them against reinvasion by a microbe they have previously been exposed to.

A new study presented at the recent conference on Innate Immunity and the Environment, organized by the European Science Foundation (ESF), revealed that insects, just like higher vertebrates, humans included, have much more in common in what concerns the immune system than previously believed.

"It is not just insect immune memories, but also how they recognize pathogens, that have close analogues in vertebrates", said the conference chair professor Paul Schmid-Hempel from the Institute of Integrative Biology in Zurich.

The research showed how the insect innate immunity enables females to make the difference between hostile pathogens and male sperm, also foreign tissue after all, in the case of some bug species. Male bedbugs and related species do not have a "taste" for the vagina, but they stab the female's abdomen instead and ejaculate directly into the blood stream, where the sperm then moves to the ovaries to fertilize the eggs.

"The point here is that for some insects sex is a violent act causing wounds that become infected and require a swift and powerful immune response. The topic was the traumatic insemination performed by some insect males, such as bedbugs, where the male injects sperm into the female through her body wall and certain sites. It has now been shown these sites are very immuno-active, and that this feature is essential to keep out infections that typically enter via the insemination act. In essence, it is about the general problem that insemination may also transfer disease and, at the same time, sperm is an antigen (non-self) for any female with all its potential immunological complications." said Schmid-Hempel.