Patient:79-year-old female Admit Reason:Bloody diarrhea (Hematocrit: 51%) Medical…

Patient:79-year-old female Admit Reason:Bloody diarrhea (Hematocrit: 51%) Medical History: Hypertension, Type II diabetes, ischemic heart disease (S/P CABG), peripheral vascular disease (S/P 2 fem-fem bypasses), CVA, recent atrial fibrillation (S/P cardioversion, on Coumadin). Transfusion History:Multiple past surgical procedures (CABG, bypasses). Blood Type: A positive DAT Results: Negative Given the patient’s medical history and that her antibody screen was negative 11 weeks ago, what was the most likely immunizing stimulus that caused her body to produce this antibody?