There seems to be a key genetic difference between males and females that is not related to sex chromosomes. Instead, it is a difference in activity between the two sexes in a specific type of immune cell which leaves females more vulnerable to some stress-related and allergic diseases.
The immune cell found in this study to put females at an increased risk for certain diseases is the mast cell. These immune components usually do not circulate in the bloodstream the way other immune cells do. Instead, they exist in tissue types all over the body fulfilling a plethora of roles such as vasodilation, angiogenesis, pathogen elimination, and even maintenance of other immune cells.
From Michigan State University, in a new study published in the journal Biology of Sex Differences, researchers picked apart and examined several genes within the RNA genome. "Over 8,000 differentially expressed genes were found in female mast cells compared to male mast cells," said lead researcher and associate professor Adam Moeser said. "While male and female mast cells have the same sets of genes on their chromosomes, with the exception of the XY sex chromosomes, the way the genes act vary immensely between the sexes."
Specifically, they saw an increase in inflammatory activity linked to mast cells in females that causes a more intense immune response to stress and allergy, resulting in diseases like irritable bowel syndrome (IBS). Doctors aren’t sure what causes IBS, but the associated symptoms seem to be consistent: abdominal pain and discomfort, changes in bowel movements, and bloating.
With this research completed, transitioning to sex-specific treatments that directly target mast cells in females specifically is definitely something that will be considered. The next question Moeser and his team will have to answer though is this: at what point to mast cells begin to act differently between males and females?
“Pinpointing when this variance happens will let us know if it occurs during adulthood or in individuals at an early age," Moeser said. "Many mast cell diseases exhibit a sex bias in children and if we can identify the timing and the mechanism of what's influencing the change, we'll have an even better understanding of how these immune cells cause disease and know when to intervene with potentially new therapies."