View metadata, citation and similar papers at core.ac.uk brought to you by CORE OPINION ARTICLE published: 08provided October by 2014 Frontiers - Publisher Connector doi: 10.3389/fimmu.2014.00424 Deciphering thymic development Harald Von Boehmer 1,2* 1 Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA 2 Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA, USA *Correspondence: [email protected] Edited by: Kendall A. Smith, Weill Medical College of Cornell University, USA Reviewed by: Herman Waldmann, University of Oxford, UK Keywords: MHC-restricted antigen recognition, T cell clones, TCR alpha/beta cDNA clones, HY antigen, TCR transgenic mice, negative thymic selection, positive thymic selection In 1979, some of us were surprised by beta genes from one T cell clone to asked Hans Georg Rammensee who was the (1) conclusion of Doherty and Zinker- another allowed us to unequivocally con- in the same office a related question. I nagel on MHC-restricted antigen recogni- clude that the MHC-restricted specificity leave it to the audience to imagine what tion following the lead of Katz, Hamaoka, was encoded by a single receptor long Michael Steinmetz told Georges Koehler and Benacerraf (2) describing the same before crystallographic studies reached or better what he did not tell him, even for the interaction of T helper cells with the same conclusion (5). This surprised though one cannot be completely sure of B cells as well as Rosenthal and Shevach some molecular biologists somewhat who it. So Georges did not produce the mice (3) describing it for the interaction of T thought that the cloning of the TCR put but Anton Berns in Amsterdam cooper- cells with macrophages. Since Doherty and an end to the mysteries of the immune ated and very nicely mapped what was Zinkernagel offered the least complicated system. required to express TCR beta genes in system, they got most of the credit. We This lead automatically to the next step, transgenic mice. Finally, the co-injection wanted to know whether a single effector the construction of TCR transgenic mice, of alfa and beta genes from an HY spe- cell was involved and therefore analyzed a to analyze the selection of T cells accord- cific clone was done by Horst Bluethmann clone of cells, specific for the HY trans- ing to their specificity. Initially, we were at Hoffmann La Roche in Basel where plantation antigen. If it could be shown interested to test the ideas of Burnet and Michael Steinmetz had moved. When the that the progeny of a single cell was MHC Lederberg that autoaggressive cells were mice had grown up, we tested them with restricted, we had something to explain, eliminated in primary lymphoid organs. a variety of reagents prepared for this which was not obvious. The cloning in For this reason, we used again the genes of task and could report on the deletion of Basel worked fine, with the competent help HY specific clones since then we could eas- CD4C8C cells in male mice even though of Hans Hengartner before his departure ily compare female and male mice. Here, these mice came with an anomaly, the too to the lab of Zinkernagel in Zurich. The I have to tell a little tale that charac- early expression of the transgenic TCR, clone was in fact MHC restricted, telling terizes (some?) scientists: it was Michael which made proper quantitation difficult us that MHC restriction was the property Steinmetz, who had previously spoken to (6). Only recently could we address this of a single cell. The same conclusion was Fritz Melchers, who asked at the Reisens- problem and reported deletion of CD4C8C derived from experiments with Matthias burg in the South of Germany whether thymocytes in the absence of TCR edit- Wabl, who observed the killing of targets there would be any interest in generating ing (7). This ended a long story on the by single killer cell (4). The clone was TCR transgenic mice. I answered with a deletion of autoaggressive cells at a cer- also alloreactive, which was observed prior clear yes saying that this would allow to tain stage of development, something that to the realization that a significant por- test Burnets and Lederbergs ideas. So, it had not been addressed in mice express- tion of T cells carried two receptors and was concluded to go ahead and initially ing superantigen specific receptors, which thus it is unclear to date whether a sec- Georges Koehler was singled out as the somewhat compromised our transgenic ond receptor was involved or not. This was scientist residing by now in Freiburg to approach since they were conducted later just the first example of a clone, which help with the construction of mice since he and yielded results earlier albeit with the was MHC restricted and HY specific as had succeeded to generate immunoglobu- limitation that the conclusions had to be well as H-2Dd specific and this overlap lin transgenic mice. I was therefore mildly restricted to superantigens (8) whereas in specificity was subsequently observed surprised when one day Georges entered we dealt with conventional antigens for in other clones such that the high fre- my lab and asked me whether I could T cells. quency of alloreactive T cells is not really give him an HY specific clone since he The next step was related to positive an issue. had the idea of testing Burnets and Leder- selection and the matching of specificity Follow up experiments with the Michael bergs ideas. I told him that this sounded and function. Here, the first realization was Steinmetz lab transferring TCR alfa and familiar, he blushed only a little and then that a receptor derived from a CD8C cell www.frontiersin.org October 2014 | Volume 5 | Article 424 | 1 Von Boehmer Deciphering thymic development C would only be expressed on CD8 cells questions and think of clever experiments viral peptides. Nature (1989) 340:443–8. doi:10. in the transgenic mice (9, 10). The sec- to address them. 1038/340443a0 ond was that there was in fact positive 13. Deverson EV, Gow IR, Coadwell WJ, Monaco JJ, Butcher GW, Howard JC. MHC class selection as mice with inappropriate MHC REFERENCES II region encoding proteins related to the antigens not restricting the specificity of 1. Zinkernagel RM, Doherty PC. MHC-restricted multidrug resistance family of transmembrane the cell from which receptor genes were cytotoxic T cells: studies on the biological transporters. Nature (1990) 348:738–41. doi:10. obtained, failed to generate single positive role of polymorphic major transplantation 1038/348738a0 cells and thus development was arrested antigens determining T-cell restriction-specificity, 14. Trowsdale J, Hanson I, Mockridge I, Beck S, Townsend A, Kelly A. Sequences encoded in at the CD4C8C stage where cells died (9). function, and responsiveness. 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