The work of Paul Ehrlich, Frank Macfarlane Burnet and Peter Medawar, would not have been so successful if not for the previous discoveries, especially those of virologists such as Louis Pasteur and Robert Koch, however it is to them we owe our today's understanding of the immune system. Paul Ehrlich introduced the antibody formation theory explaining how antibodies, responsible for identifying and neutralizing foreign objects in our organisms, are being formed and the notion of autoimmunity, failure of an organism to recognize it's own components, resulting in an attack towards the self, which he named horror autotoxicus. Based on this knowledge and their own personal research in the field, Peter Medawar and Frank Macfarlane Burnet managed to demonstrate acquired immune tolerance, a discovery which was later rewarded with a Nobel Prize in 1960. It was also Peter Medawar who came up with the first – self/non-self - model of the immune system. His involvement with the issues of immunology began during the II World War, when, while conducting research on possible improvements in skin grafts, he encountered a phenomenon of graft rejection. He observed that in a case of a transplant the recipients body, as well as the graft, produce strong immunological reactions in an attempt to rid themselves from the foreign element. This strong opposition led Medawar to produce a model of the immune system based on a powerful differentiation of the self and the other. .
Even before Medawar's formulation of the immune system model, the possibilities the idea of the immune system provided in accordance to the question of people's individuality were noticed. Already in 1921 Leo Loeb, a renowned American doctor and pathologist, through the experience of the approaches towards transplantation, looked for individuality in physicality of the body terms (Loeb 1921), yet it was not until advances in immunology in the second half of the 20th century that a formulation of a theory which makes possible a physiological theory of individuation (Pradeu).
