It's not at all clear why he produced such high quality antibodies, but one theory was the sheer quantity of transfusions he had to receive after a lung operati

It's not at all clear why he produced such high quality antibodies, but one theory was the sheer quantity of transfusions he had to receive after a lung operation (something on the order of 7.4L of blood). They have no idea why he continued to produce them after, however.