Gibson and Medawar placed the laws of transplantation on a firm scientific basis. A later paper by Medawar (J. Anat. [Lond.], 1944, 78, 176- 99) demonstrated that the mechanism of rejection of transplanted tissues is immunological in character.

This "paper facilitated the later discovery of `actively acquired tolerance' and the definition of the principal laws of transplantation tolerance. Thus, it was in a series of classic experiments (stemming from this J. Exp. Biol. paper) that the field of transplantation biology was born....
This "paper is a self-contained manual for distinct forms of skin transplants in a variety of laboratory animals. There are very detailed discussions and illustrations concerning the anatomy of the mammalian integument. Importantly, the paper also provides unique information on regional variation of skin within a given animal and on the process of transplant survival or rejection. Specific discussions focus on principles of wound healing post-transplantation and on Billingham and Medawar's formative thoughts on transplantation immunity. The paper is most useful in discussing frankly the pros and cons of skin grafting as a laboratory procedure. There is considerable discussion of the pitfalls encountered in skin grafting, e.g. pigmentation and hair growth, but also the advantages, e.g. accessibility and availability for biopsy" (Santa Jeremy Ono, "The birth of transplantation immunology: The Billingham-Medawar Experiments at Birmingham University and University College London" (J. Exp. Biol, 207 (2004) 4013-4014). Digital facsimile of the 1951 paper from cob.silverchair-cdn.com at this link.

In 1960 Medawar shared the Nobel Prize in Physiology or Medicine with Burnet for "the discovery of acquired immunological tolerance."  See also Nos. 2578.4, 2578.11, 2578.12, and 2578.24.

Proof of Burnet and Fenner’s theory of immunity. For their discovery of acquired immunological tolerance Medawar and Burnet (No. 2578.7) shared the Nobel Prize in 1960.

Experimental production of immunological tolerance by Billingham and colleagues.Paper II distinguished adoptive from passive immunization. E. M. Sparrow was a co-author of paper I.

Medawar showed grafting to be unsuccessful when donor and recipient animals came from the same litter, unless the two are genetically identical – another instance of the delayed hypersensitivity reaction.