157 years ago today, on June 14, 1868 (April 24, 1868), Landsteiner, the discoverer of the ABO blood group system, was born. Karl Landsteiner, a famous Austrian medical scientist and physiologist, was born in Vienna, the capital of Austria, on June 14, 1868. After graduating from the Medical School of the University of Vienna, he continued to stay in school and study chemistry. For discovering the first three of the four blood types A, B, O, and AB in 1900, he won the Nobel Prize in Medicine and Physiology in 1930. Died in 1943. In 1900, while working at the Vienna Institute of Pathology, Landsteiner discovered that the serum of person A sometimes coagulated with the red blood cells of person B. This phenomenon did not receive enough attention from the medical community at that time, but its existence was a very serious threat to the patient's life. Landsteiner was very interested in this issue and began serious and systematic research. After a long period of thinking, Landsteiner finally thought: Could it be that the blood of the transfusion person mixed with the blood in the recipient's body caused pathological changes that led to the death of the recipient? In 1900, he cross-mixed the normal blood of 22 colleagues and found that there was a reaction between red blood cells and plasma, that is, some plasma can cause the red blood cells of others to agglutinate, but some do not. So he compiled the results of the blood experiments of 22 people in a table. After carefully observing the table, he finally found that human blood is divided into many types according to the different antigens and antibodies in red blood cells and serum. So he divided the blood types in the table into three types: A, B, and O. When blood of different blood types is mixed together, different situations will occur, and clotting and hemolysis may occur. If this phenomenon occurs in the human body, it will endanger people's lives. In 1902, two students of Landsteiner expanded the scope of the experiment to 155 people and found that in addition to the three blood types A, B, and O, there is a relatively rare fourth type, later called AB type. In 1927, it was recognized by an international conference and adopted Landsteiner's original letter naming, that is, there are four types of blood types A, B, O, and AB, and the modern blood group system was officially established. Landsteiner was also awarded the Nobel Prize in Medicine and Physiology in 1930 for his significant contributions. Landsteiner's research found the main reasons for the failure of blood transfusions in the past, providing theoretical guidance for safe blood transfusion. But at that time, many people did not see the significance of this scientific discovery in medicine, so Landsteiner did not become famous for it. It was not until an accident eight years later that he became famous. In 1908, Landsteiner left the Vienna Institute of Pathology and went to work as a doctor at the Werheimina Hospital, the hospital where he often played as a child. One spring morning, a woman's cries came from the lobby of the Wehemina Hospital. Landsteiner happened to pass by here and stopped to watch. It turned out that her child was sick and had a fever, and a few days later, he was paralyzed of his lower limbs. There was nothing the doctors could do about it. They thought it was an incurable disease and powerless to do anything about it. In a desperate situation, what could the woman do but cry? Landsteiner couldn't help it. He carefully examined the sick child and seemed to think that there was more than just a dead end, because according to the results of his years of research, there is a theoretical basis for treating this disease, but there is no successful experience. Landsteiner told the child's mother about the situation, and the desperate mother seemed to see a glimmer of hope again. She decided to give Landsteiner a try. Landsteiner used the principle of serum immunity to transfuse the cause of the patient's disease into a monkey. After the monkey produced antibodies, the monkey's blood was made into a serum containing an antibody, and the serum was inoculated into the patient. The sick child was quickly treated. Landsteiner became famous. Austrian medical experts acknowledged his talent, and the University of Vienna hired him as a professor of pathology. But Landsteiner's main concern was blood type research. His work was not taken seriously in Austria, so he moved to the Rockefeller Institute of Medicine in the United States as a researcher. At that time, four blood types A, B, AB, and O were used for blood transfusion, and occasionally hemolysis occurred naturally after transfusion of the same type of blood. This is a great threat to the safety of patients. In 1927, Landsteiner and American immunologist Philip Levin jointly discovered M, N, and P factors in blood, thus more scientifically and completely explaining the hemolysis reaction of some multiple transfusions of the same type of blood and neonatal hemolysis in obstetrics and gynecology. Landsteiner's outstanding contributions to the outstanding research results of human blood types not only provide a scientific theoretical basis for safe blood transfusion and treatment of neonatal hemolysis, but also have great significance for immunology, genetics, and forensic science.