Study reveals how UV rays from the sun activate the immune system and flare up disease in lupus.
- Lupus occurs in women in 90% of cases and most often begins between puberty and menopause with a peak frequency between 30 and 39 years, according to Health Insurance.
- In mainland France, Health Insurance estimates that 41 people out of 100,000 suffer from systemic lupus erythematosus.
The link between ultraviolet (UV) radiation and disease flares in lupus is well known: after exposure to the sun, people with systemic lupus erythematosus (SLE) frequently develop skin rashes, which are often accompanied by an outbreak of the disease as a whole. But the reasons for this mechanism are poorly understood.
Lupus affects different organs
Systemic lupus erythematosus (SLE) is an autoimmune disease whose term lupus evokes a characteristic symptom of this condition: a rash on the face, in the form of a mask called wolf (from the Latin lupus), according to theHealth Insurance. The immune system produces specific antibodies called autoantibodies and a variety of white blood cells called lymphocytes.
The disease is responsible for inflammatory reactions and damage to various tissues: vessels, skin, joints, muscles, blood cells… and exposure to the sun and UV light cause people with lupus to have more self- antibodies in their blood. It affects internal organs like kidneys, heart and lungs without knowing exactly why.
We now know a little more thanks to American researchers from the Hospital for Special Surgery (HSS) in New York.
Photosensitivity: poor lymphatic flow is involved in lupus
In their study presented at ACR Convergence 2022, the annual meeting of the American College of Rheumatology which took place from November 10 to 14, they explain that they have found an underlying mechanism that explains this association: a decrease in lymphatic drainage.
This is because people who suffer from lupus have a poorly functioning lymphatic system and this is what contributes to both photosensitivity – an increase in the skin’s sensitivity to sunlight, and an immune response in the lymph nodes. lymphatics that cause a flare-up of the disease.
The researchers studied skin biopsies from lupus patients as well as healthy volunteers who served as controls. When they examined the samples from patients with lupus, they found that the lymphatic vessels, which include the function of removing fluid and cells from the skin, were more dilated than those of healthy controls. This helped prove that people with lupus have poor lymphatic flow.
Lymphatic drainage reduces the effects of this autoimmune disease
They then studied mouse models of lupus, using a dye injected into the skin to visualize the flow of lymphatic fluid. They found that when lupus mice were exposed to UV light, more of the dye remained in the skin. This proved that the lymphatic vessels were not draining fluid as well as they should, the study authors explain.
By using manual lymphatic drainage techniques to manipulate and help the flow of lymphatic fluid drain well, researchers have seen improvement. Indeed, lymphatic drainage performed in lupus mice reduced the number of plasmablasts and germinal center B cells, cell types known to be important players in lupus.
The researchers thus believe that manual lymphatic drainage could be beneficial for patients with lupus, especially after exposure to the sun.