Immunology as an independent discipline is just I 00 years old. In the Pasteurian era, it was the direct handmaiden of medical microbiology, but with Landsteiner's discovery of the blood groups in I 90 I , immunology burst through into other fields. This spreading of immunology into many facets of biology and medicine has con- tinued at an accelerating pace, particularly over these last 20 years. For the physician, immunology is a 'horizontal' specialty, breaking the confines of a single organ system and touching an enormous number of chronie diseases. This spreading tendency of immunology is...