This ninth edition of Essential Immunology has been revised and revamped with the addition of full colour diagrams and photographs. Summaries at the end of each chapter will be boxed to make them more user-friendly. The ninth edition will delineate basic from advanced text by using a colour tint behind the more detailed information. In this way, the student will be able to tailor their reading to the situation. The ninth edition has updated sections on: * cellular signalling in the immune system * hormonal regulation of the immune system * positive suppression of the hypersensitive response * mucosal immunity * the roles of TH1 and TH2 cells * epitope specific vaccination