Q. A 46-year-old African American woman visits the outpatient clinic because of difficulty in swallowing (dysphagia). The patient's medical history is significant for gastroesophageal reflux and carpal tunnel syndrome. Vital signs show no abnormalities. Upon examination, the patient has non-pitting edema, and skin tightening is noted in both hands with multiple dilated capillaries. Cardiac and chest auscultations reveal no abnormality. The patient is admitted for further investigation. No major organ abnormalities are identified. Which of the following immunological markers is likely elevated in the above patient?