The stl. file was prepared by three immunology students (Sophie, Manon and Margot) at the University of Toulouse (http://www.univ-tlse3.fr/) and allowed to print the MHC class II molecule. This "Thing" was made within the frame of a pedagogical scenario aiming at introducing the students to the examination and handling of 3D structures and resulted in the making of a gallery of portraits of molecules with immunological interest. Printing was done at the CampusFab (https://fablab.univ-tlse3.fr/wiki/index.php/Accueil), the LabLab of the University (twitter account: @fablabups.)The 3D structure of the protein was recovered from the protein databank (http://www.rcsb.org/pdb/home/home.do) with the accession number xxx It was downloaded using the .gz extension. Then, the structure was adapted for 3D printing using the Chimera software (http://www.cgl.ucsf.edu/chimera/) and saved using the .stl extension. It was printed on a Leapfrog CreatrHS (http://www.lpfrg.com/creatr-hs) using the Simplify 3D (https://www.simplify3d.com/) software.