Suppressive Functions of Regulatory T Cells in Migraine

Migraine is a major and global public health concern that affects 14% of the population worldwide. It is 2 to 3 times more prevalent in women than men and is the second leading cause of disability. Many patients remain unresponsive to currently available treatments. As evidenced in different studies, including our own, several auto-immune and inflammatory disorders, such as multiple sclerosis, are associated with a higher prevalence of migraine and a higher risk for migraine chronification (at least 15 headache days per month) compared to the general population. These findings suggest that inflammation may play an important role in migraine chronification. Cytokine and immune cell dysregulations have been evidenced in the disease but the role of inflammation in migraine pathophysiology remains unclear. Among T lymphocytes, regulatory T (Treg) cells play an important role in maintaining immune homeostasis. They regulate pro-inflammatory effector T (Teff) cells and proinflammatory cytokine release (IL-6, IL-17, interferon-γ) through different suppressive mechanisms such as the hydrolysis of pro-inflammatory and nociceptive adenosine triphosphate (ATP) into anti-inflammatory and antinociceptive adenosine (ADO), by Treg surface enzymes CD39 and CD73, present on 40% and 6-10% of Treg cells, respectively. ADO then suppresses Teff cells by binding to their ADO receptor A2A. ATP is involved in the transduction of pain signals in migraine and its insufficient hydrolysis can lead to pain chronification. It has been evidenced that Tregs naturally suppress interferon (IFN)-γ production by Teff cells. Their CD39-positive (CD39+) subsets also suppress IL-17 production by Teff cells, whereas CD39-negative (CD39-) Tregs seem to increase IL-17 secretion. Recent studies have shown altered Treg proportions in migraine compared to controls and Treg subpopulation dysregulations, such as decreased CD39+Treg cell levels. This further suggests that Treg suppressive functions may be altered in migraine, but no functional assays have been led to confirm that. In this study, the investigators aim to determine whether Treg cells play a role in migraine pathophysiology, by answering the following 3 separate questions: Question 1) Are Treg suppressive functions decreased in migraine patients? Question 2) Are CD39+Treg cells functionally deficient in migraine patients? Question 3) Is the hydrolytic activity of enzyme CD39 reduced in migraine patients? Through Treg/Teff coculture the investigators will assess the ability of total Treg and CD39+Treg cells to inhibit Teff proliferation and pro-inflammatory cytokine secretion and measure the hydrolytic activity of Treg enzyme CD39 on ATP in chronic migraine patients versus healthy controls. The use of human immune cells (Treg and Teff lymphocytes) in our experiments will allow the investigators to better understand migraine pathophysiology, with a direct application to human subjects, as well as to avoid animal testing and suffering. Through its animal-free setting, following the 'Reduce, Refine, Replace (3Rs)' principle, the investigators wish to promote animal-free research and the reduction of animal use for reagent production by using recombinant antibodies for flow cytometry and synthetic medium supplements for cell culture. This study will lead to a better understanding of the role of inflammation and Treg cells in migraine pathophysiology and will provide new perspectives for the development of personalized treatments according to the immune pain profile of migraine patients. The investigators aim to show that Treg suppressive functions are altered in migraine and that the ADO pathway is deficient. Through Treg/Teff coculture the investigators will measure the ability of Tregs to inhibit Teff proliferation and cytokine secretion and assess the CD39-related hydrolytic activity of Tregs. This will allow the investigators to study Treg cells suppressive functions on Teff cells in female patients with chronic migraine and healthy female control participants.