supported by the Deutsche Forschungsgemeinschaft(DFG);C.F.is thankful for funding by the DFG(FR-1325/17–1,SFB958(project Z03);TRR186(projects A05,A11));M.A.-B.is thankful for funding from the Freie Universität Berlin Forschungskommision.
Classical human leukocyte antigen(HLA)molecules of the major histocompatibility classⅡ(MHCⅡ)complex present peptides for the development,surveillance and activation of CD4^(+) T cells.The nonclassical MHCⅡ-like pro...