Karl Landsteiner

Discovered human blood groups, revolutionizing transfusion medicine and saving millions of lives

Karl Landsteiner (1868-1943) made an epochal contribution to medical science through his discovery of blood types. In 1901, he identified the ABO blood group system, explaining why blood transfusions sometimes caused fatal reactions. This breakthrough laid the foundation for safe blood transfusion practices.

Before Landsteiner's discovery, blood transfusions were risky procedures with unpredictable outcomes. His systematic experiments mixing blood samples revealed agglutination patterns, leading to the classification of blood into groups A, B, AB, and O. This work earned him the 1930 Nobel Prize in Physiology or Medicine.

Landsteiner further contributed to immunology by discovering the Rh factor in 1937 with Alexander Wiener. These discoveries became crucial for:

• Modern surgery protocols
• Maternity care (preventing erythroblastosis fetalis)
• Forensic science applications

His legacy continues through organizations like the American Red Cross, which manages blood donations using his classification system. Over 100 million blood transfusions occur annually worldwide thanks to Landsteiner's foundational work.