Key Mechanisms of Abnormal T Cell Activation and Differentiation in IgG4-Related Ophthalmic Disease

IgG4-related disease (IgG4-RD) is a newly recognized chronic inflammatory condition caused by immune system dysfunction. It is characterized by the infiltration of IgG4+ plasma cells, dense fibrosis, and inflammation involving veins and eosinophils. Common symptoms include elevated serum IgG4 levels and the formation of tumor-like growths that can affect almost any organ, leading to pressure on tissues, irreversible damage, and even organ failure. While estimates suggest a prevalence of 0.28 to 1.08 per 100,000 people, this might be an underestimation due to limited awareness, the new definition of the disease, and its subtle onset. IgG4-related ophthalmic disease (IgG4-ROD) is a subtype of IgG4-RD that affects the eye area, particularly the lacrimal glands, extraocular muscles, and surrounding nerves. It often presents as painless swelling of the lacrimal glands in one or both eyes, sometimes with discomfort or a sensation of a foreign body. It can also cause thickening of eye muscles, leading to symptoms like bulging eyes, blurred vision, or double vision. In some cases, mass lesions in the orbit may press on the optic nerve, potentially leading to permanent vision loss. While there is currently no cure for IgG4-ROD, steroids are used as the main treatment to control inflammation and fibrosis. However, the disease often recurs, with recurrence rates for IgG4-RD reported between 24% and 63% in various studies. Understanding the causes of IgG4-ROD could help develop better treatments and reduce the chances of relapse. Studies suggest that T cells play a key role in the development of IgG4-RD, including IgG4-ROD. CD4+ T cells are the main immune cells found in affected tissues. They can help B cells multiply and produce IgG4 antibodies and contribute to tissue fibrosis by releasing certain signaling molecules. Despite treatment with rituximab, a drug that targets B cells, many IgG4-RD patients experience relapses, indicating that T cells remain important in driving