The immune systems of men are no match for those of wives and girlfriends because women have micro RNAs -- short strands of RNA encoded on the X-chromosome, The Daily Telegraph reported.
Dr. Claude Libert of Ghent University in Belgium said men are at a disadvantage since they only have one X chromosome while women have two so even when immunity genes are silenced on one, the other can compensate.
"Statistics show that in humans, as with other mammals, females live longer than males and are more able to fight off shock episodes from sepsis, infection or trauma," Libert told the Telegraph. "We believe this is due to the X chromosome which in humans contains 10 percent of all micro RNAs detected so far in the genome [genetic code]."
Biologically, the difference might have evolved because women are more likely to ensure the survival of the species so they can resist infection while pregnant or raising a child, Libert said.
The findings were published in the journal BioEssays.