When I first began to think about this presentation I flirted with the idea of reversing the title to read: ‘Immunologists as Parasites’. I could clearly see some of the sectional headings such as ‘The Spreading Cancer of Tumour Immunology’ and ‘Does the International Immunology Scene represent an IDIOT-ype–Anti-IDIOT-ype network’?. But although this might have been fun it would certainly have been unfair to those immunologists who are currently working on Parasite Immunology, a very difficult and demanding field.