Five Quarts_ A Personal and Natural History of Blood - Bill Hayes [93]
But first he led a winding route from the Label & Release room to a set of windows overlooking another work space. The sight of two white-coated scientists huddled over computers wasn’t all that fascinating, but the work these gentlemen were doing certainly was, Richard assured me. He gestured grandly. “This is our Immuno-Hematology Reference Laboratory. It is very much a part of the history of blood banking, one of the oldest in the country, and one of the most famous.” Perhaps he could tell by the look on my face that I’d gotten lost on the way through his hyperbole. Richard paused, then rewound his narration. “You know, each individual has a ‘genetic fingerprint,’ if you will, on his red cells—”
“Right. Not a DNA signature, but a kind of tag that identifies your blood group.”
“Yes,” he nodded. “And the most significant in transfusion therapy are the best known—A, B, AB, and O.”
Sure, anyone who’s donated blood knows these letters. And of course I couldn’t help noticing them prominently displayed on every blood product. This hematological safety code devised in 1901 put an end to hundreds of years of dangerous blood transfusions, I knew. As is often the case with scientific breakthroughs of this sort, the discovery of blood types began unceremoniously, with a curious individual trying to unknot a puzzle. Austrian pathologist Karl Landsteiner could not fathom why adding a bit of one person’s blood into test tubes of other people’s blood caused such varying results. Sometimes the red cells bunched together, sometimes they burst, and sometimes there was no reaction at all. Now, this was not an unknown phenomenon. Earlier scientists had concluded that these cellular dynamics were due to a clash between healthy and sick blood. Landsteiner, however, was using only the blood of healthy subjects, including his own. With the kind of glee I imagine only the fussiest scientists having, Landsteiner pulled out his graph paper. He mixed and mixed and mixed, taking careful notes and charting his findings. Patterns emerged, and he identified three groupings of blood—blood groups—which he labeled A, B, and C. (C later became O.) As it turned out, Landsteiner belonged to this last group, type O, making him what is now called a universal donor. In terms of his experiment, this meant that his red cells didn’t react to any other specimens, which, in an odd way, is the aspect of his story I enjoy most. Even his cells, it seems, were dispassionate observers.
In a more technical sense, what Landsteiner had documented was a classic antibody-antigen response. For the purpose of illumination, consider a patient with type A blood (which means his red cells have the A antigen). If wrongly infused with type B blood, his body will immediately launch an assault: his antibodies versus the foreign red cells. (A similar scenario will play out if a type B patient is given type A blood, or if a type O patient is transfused with either A or B blood.) It’s not surprising that, in his initial experiment, Landsteiner missed the fourth blood type, AB, which, for example, is found in only 4 percent of the U.S. population. These individuals are called universal recipients because they can safely receive any blood type.
One last major antigen is noteworthy here, antigen D, whose presence or absence is indicated with an Rh+ (“Rhesus-positive”) or an Rh-. If an Rh- woman is carrying an Rh+ child, the mother-to-be may produce antibodies that will threaten the baby’s life, a condition that, fortunately, can be identified and treated. Karl Landsteiner co-discovered the Rh blood factor in 1940, ten years after winning the Nobel Prize for his ABO blood grouping system.
Richard cleared his throat. In addition to the A’s, B’s, and D’s, he explained, “There are literally hundreds of other antigens and proteins—both on the red cell surface and embedded in the red cell membrane