The full-length form, the soluble form, the ligand-independent form, and the form containing only exons 1 and 4. In our experiments, the full-length form of CTLA-4, which is a representative immunosuppressive form of CTLA-4, was expressed in the CT26 tumor tissues. On the other hand, we found that CTLA-4 was not expressed in the cultured CT26 cells, although it was strongly expressed in the CT26 tumor tissues. IgG4-related disease was first described in patients with autoimmune pancreatitis who had elevated concentrations of IgG4 in serum. Shortly thereafter, in 2003, extra-pancreatic lesions were described in patients with autoimmune pancreatitis, which led to the recognition of IgG4-RD as a systemic condition. Since 2003, IgG4-RD has been described in a multitude of organ systems including the pancreas, biliary tree, salivary glands, kidneys, lungs, skin, prostate, and orbit. Across the various organ systems, IgG4-RD is known to have a similar histopathological LDK378 presentation which includes a dense lymphoplasmacytic infiltrate that is rich in IgG4+ plasma cells, storiform fibrosis, and obliterative phlebitis. Ophthalmic disease is a common manifestation of IgG4-RD. Patients with IgG4-immunostaining, may present with painless eyelid swelling, proptosis, or diplopia. The lacrimal glands, the nasolacrimal duct, and the retrobulbar region may be affected. A consensus report recommended the term, IgG4-related dacryoadenitis for disease in the lacrimal gland and IgG4-related orbital inflammation for disease that affects adipose tissue just posterior to the ocular globe. Orbital inflammatory disease can affect orbital muscle, lacrimal gland, or adipose tissue. The most common systemic disease associated with orbital inflammation is hyperthyroidism attributable to Graves disease, also known as thyroid eye disease or TED. Sarcoidosis or granulomatosis with polyangiitis can also cause inflammation within the orbit. Many patients with orbital inflammatory disease are classified as having nonspecific orbital inflammation. Little is known as to how each of these entities might be related to IgG4-RD. The etiology of IgG4-RD remains unclear. Although the infiltration of IgG4+PC is a defining characteristic of the disease, there is no evidence that IgG4 is directly involved in the pathogenesis. In fact, some have hypothesized that IgG4, which does not fix complement, is expressed to dampen inflammation. Intriguingly, an immune response to IgG4 reportedly exacerbates rheumatoid arthritis. Three studies that sought to determine the prevalence of IgG4 – immunostaining among patients with orbital inflammation found very discrepant results with prevalence ranging from 4 to 52%. In part, this relates to the definition of a positive case. Some studies have used a threshold of 10 IgG4+PC/high powered field. Other studies have used thresholds of up to 30 IgG4+cells/hpf or a minimum ratio of IgG4+:IgG+PC of 0.40 or a combination thereof. Some have suggested that IgG4- immunostaining has immense clinical implications that frequently indicate a multisystem disease which is highly likely to respond to rituximab therapy. Accordingly an understanding of the prevalence of IgG4 immunostaining among patients with orbital inflammation has potential clinical and therapeutic implications. We sought to clarify the implication of IgG4 immunostaining in the orbit by studying tissue from patients with a variety of orbital inflammatory diseases. We correlated the detection of IgG4+ plasma cells in tissue with the specific diagnosis as well as with inflammation, fibrosis, and gene expression. The diagnoses of nonspecific orbital inflammation, sarcoidosis, granulomatosis with polyangiitis.