Mitchison discovered the transference of
transplantation immunity by
sensitised cells, thereby providing evidence relating transplantation immunity to
hypersensitivity reactions of the 'delayed' type. He devised a method for revealing mixtures of cells of different
genotypes
in vivo and used it to be equal first in demonstrating that the 'radiation recovery factor' is a
graft of living cells and not a
humoral agent. He carried out the most exact quantitative analysis of tolerance hitherto attempted in a cellular system and proved that persistence of tolerance depends on persistence of
antigen. == Awards and honours ==