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In the first four editions, I wrote the entire book except for the HLA chapter, which was done by my good friend and former fellow, Yoon Choo. For this fifth edition, it seemed appropriate to begin to involve others but I wanted to keep this as a Minnesota book. Thus, I invited some former fellows to assist with this edition. These authors represent quite a range of stages of the fellowship program. David Stroncek dates back to the 1980s and the early days of unrelated marrow transplants to more recent fellows Tom Gniadeck and Stephanie Kinney who has provided a new chapter on pediatric transfusion medicine. Two authors are from countries other than the United States: Vincent Laroche from Canada and Ulrike Konigbauer from Germany, whose husband Josef was a wonderful musical and scientific mentor to one of my sons. One of the authors (Ram Reddy) retired after preparing his chapter and sadly another author (Randy Coven) died unexpectedly during the preparation of this book. Another former fellow and good friend, Phyllis Warkentin has not authored any chapter in the book but is acknowledged in the chapter on cellular engineering for her work in establishing our first bone marrow‐processing laboratory, which ultimately led to the current sophisticated comprehensive facility at University of Minnesota, which provided the initial venue for doctors McKenna and Stroncek, who have co‐authored the above‐mentioned chapter in this book.

Tom Watkins deals with the blood donor situation which continues to be a challenge; Gary Bachowski the complex evaluation of donors and blood collection, and Alecia Kaplan component production and the wide variety of resulting components and Nancy Van Buren the complex laboratory testing of donated blood. Sarah Ilstrup brings us up to date with blood groups and ulrke Konigbauer the extensive process of getting the right blood components to right patients at the right time and safely. Vincent Laroche educates us about clinical uses of blood components and Jim Stubbs elaborates on some special clinical situations. Scott Koepsell summarizes current perspectives on transfusion complications. Dave Mckenna and Dave Stroncek provide a wonderful chapter on exciting novel blood related cellular products.

Preparing the preface for this fifth edition provides a nice opportunity to reflect on the evolution of the content of these five editions. There are still challenges in recruiting adequate number of donors to maintain a regular supply of blood, given the demographic evolution underway and its impact on potential donor availability. This has led to discussions on paying donors, which would have been unthinkable at the time of the first edition. Blood centers evolved from multifaceted community hubs into manufacturing sites almost entirely focused on blood collection, having shed most of the exciting diverse activities they carried out during a couple of decades.

The organizations that provide the supply have gone through mergers and are now operated almost like a commodity business with substantial competition. While this might have been inevitable, I find it unfortunate.

Collection and production of traditional blood components has changed very little and still involves putting complex multiple bag systems into a centrifuge and then separating the plasma from red cells, much as was envisioned by Carl Walter in the 1950s, but now with far more complexity.

Collection of blood products by apheresis has continued to thrive and essentially all platelets in the United States are now produced by apheresis. Unimagined in the first edition is collection of a modest portion of red cells by apheresis. Therapeutic apheresis has evolved for the most part away from blood banks and transfusion medicine but is widely used to treat a variety of conditions.

A major development in transfusion medicine during these five additions relates to blood safety and transfusion‐transmitted infections. Blood safety has continued to improve with current rates of test positive units of less than one in a million. Infectious agents have come and some have gone. Our good fortune is that respiratory viruses such as influenza and, more recently, SARS Co‐V are not transmitted by blood transfusion. We have arrived at the point where bacterial contamination of platelets is now the major transmissible infection risk.

Pathogen reduction, a paradigm shift in approach to blood safety, has progressed much more slowly than I imagined. It is disappointing that more than 20 years after some of these initial efforts, there is only one technology approved in the United States and that is for platelets and plasma but we still have no approved PR technology for whole load or red cells. While these PR technologies are not particularly scientifically complex, applying them to the world’s blood supply has been difficult and expensive, resulting in disappointingly slow progress. This is probably due to multiple factors: the cost of developing and implementing the technology, unrealistic and unreasonable expectations of how the technology will perform, failure of leadership of transfusion medicine and blood banking to enthusiastically support and assist in the development of this technology, and failure of regulatory agencies to be open‐minded and recognize that these are first‐generation technologies. Clearly, this is the future of blood safety; we just need to get the right technologies and get them implemented.

The use of plasma derivatives, particularly IVIG, has grown enormously, leading to the establishment of many centers for collecting plasma from paid donors in the United States. In fact, these US paid plasma donors form the basis for a large portion of the world’s plasma derivative products.

The molecular basis of blood groups has now been determined and some molecular testing is making its way into practice. Little of this was known at the time of the first edition.

Granulocytes for transfusion continue to be a fringe product and it is surprising that after almost 50 years, their clinical value has never been established. The trial (RING) that probably would have settled this was unfortunately halted prematurely due to ending of NIH funding for this work.

Quality systems was an appendix to the first edition because i had written the book before deciding to include the topic. This expertise has been introduced into blood banking and is now an integral part of our regular operations in the collection and production of blood products as nicely described by Kristen Mascotti, whose career has evolved along this pathway. These concepts have extended into clinical care as evidenced by patient blood management.

At the writing of the first edition, I expected that by now, we would have a red cell substitute oxygen carrier but this has not happened despite considerable investment by several companies. Nor are there “synthetic” platelet products, although exciting developments are underway. While producing blood components such as red cells and platelets from stem cells in a laboratory is scientifically exciting, this is unlikely in the near future.

In the first four editions, there was a separate chapter on hematopoietic growth factors, but these have settled into their place in transfusion medicine and are now included in other chapters.

There are some interesting cycles in our field of transfusion medicine. Whole blood has evolved from efforts to convert clinicians to the use of packed red cells but now is making a comeback in the management of acute blood loss and trauma. Dr. Stubbs has been a leader in these therapies and provides a nice summary of that in his chapter. Another interesting cycle is platelet storage. In the 1970s, this was done in the refrigerator until the seminal report by Murphy and Gardner, which led to room temperature storage. Cold stored platelets are making a comeback, partly driven by the desire to extend the shelf life and to cope with possible bacterial contamination of the platelet product. Ironically, it appears that cold stored platelets might have special therapeutic advantages. Another interesting cycle is paying donors. When I was a resident, we paid donors at the University of Minnesota hospitals donor center, but this practice was discontinued and considered inappropriate for many years. Now, a plan to pay donors has resurfaced and the first of these high‐quality paid platelet donor centers has been established just about a mile from my house.

Many of us in the United States have been able to develop a global perspective because of the variety of interactions and friendships that developed during the era reflected by these five for additions. This was also partly facilitated by the President’s Emergency Plan for AIDS Relief (PEPFAR), which provided support for blood banking and transfusion medicine work in many countries and, for instance, made it possible for me to work in Afghanistan along with several other countries in sub‐Saharan Africa.

Over the years, it has been a pleasure to work with the staff at Wiley, the publisher who has done all additions after the second. They have done a great job of producing, marketing, and distributing these multiple editions of the book.

Well now it has come to this. It has been a pleasure to write and produce this book for you and an honor that you found it valuable enough to obtain it. I hope this most recent edition will continue to meet your needs and help guide you in your career. I do not know whether there will be a sixth edition and if so whether I will be part of it. So I wish you a successful career and I hope this book might help you along the way.

My great admiration, affection, and respect for all those who passed through our fellowship program and those of you who have been kind enough to be a colleague and to include me in your life.

First you were of me and now I am of you.