The history of this text started years ago after reading Wittgenstein-s -Tratactus Logico-Philosophicus-. At some time later, it seemed to me a good idea to follow the -tratactus- structure to attempt to write a minimal description of the immune system. I finally did it for fun and hopefully to be useful to whomever reads it.The text reflects my own personal view of the vertebrate-s immune system (IS). It is centered on concepts and ideas that were developed since 1986 based on work from my own lab1 and from Benedita Rocha-s lab2 and I-m greatly indebted to her for this. I have kept it short and focused on what I believe are the essential features of the IS. I-ve tried to avoid too much detail and most of the complex immunology jargon. If some now fashionable aspects of the IS are only superficially mentioned it is because I feel that they may be not so relevant after all. Perhaps for all these reasons I give no detailed sources and simply refer the reader to some general inspiring non
