The book begins with a refresher of basic descriptive immunology and soon moves to concepts such as TRALI, transfusion reactions, alloimmunization, TRIM, complications to transplantation, HLA-incompatibility, responses in adults versus neonate/pediatric patients and more, even including state-of-the-art topics such as polyclonal/monoclonal therapies and CAR T. The authors encourage readers to see these chapters as their effort to increase levels of awareness of blood usage and use what is learned from what is described to continue to make transfusions safer.