This study evaluates the effect of erythropoietin on the number and function of regulatory T cells in adults with autoimmune hepatitis. Participants will receive a single dose of erythropoietin, and then the investigators will collect blood at different time points for analysis of regulatory T cell number and function.

There is data from the laboratory that erythropoietin helps stimulate regulatory T cells, a type of immune cell which is thought to combat autoimmunity, but this study will look at whether it does the same thing in adults with autoimmune hepatitis.

Inclusion Criteria:

• Diagnosis of autoimmune liver diseases (autoimmune hepatitis, autoimmune cholangiopathy, or primary biliary cirrhosis or primary sclerosing cholangitis with hepatic autoimmune liver disease or overlap syndrome) confirmed on liver biopsy
• Use of immunosuppressive therapy (prednisone, azathioprine, 6-mercaptopurine, mycophenolate mofetil) for the treatment of the autoimmune liver disease
• Stable immunosuppression regimen at least 6 months prior to enrollment
• Ability to provide verbal and written informed consent

Exclusion Criteria:

• Diagnosis of decompensated cirrhosis (defined by presence of ascites, varices, encephalopathy)
• Hemoglobin above average normal value (15.7 g/dL in men, 13.8 g/dL in women)
• Alanine aminotransferase greater than 2 times upper limit of normal (33 IU/L in men and 25 IU/L in women)
• Uncontrolled hypertension with systolic blood pressure greater than or equal to 160 or diastolic blood pressure greater than or equal to 100
• End-stage renal disease on hemodialysis
• History of venous thromboembolism including deep vein thromboses or pulmonary emboli
• History of stroke
• History of heart failure
• History of seizure disorder
• History of significant cardiovascular disease including a history of myocardial infarction
• Active malignancy (untreated or undergoing therapy)
• History of pure red cell aplasia
• History of intolerance or allergy to erythropoietin
• Known hypersensitivity to mammalian cell-derived products
• Known hypersensitivity to human albumin
• Presence of vascular access
• Prior recipient of erythropoietin within 12 weeks of the study
• Patient unable to provide consent including infants, children, teenagers, prisoners, cognitively impaired adults
• Non-English speaking
• Pregnancy