Absence of MHC class II on cDC1 dendritic cells triggersfatal autoimmunity to a cross-presented self-antigen

摘要

Conventional dendritic cells expressing the XCR1 chemokine receptor (cDC1s) excel at cross-presentation. Here,we developed and used a mouse model in which a Cre recombinase is expressed under the control of the Xcr1gene while preserving XCR1 expression. We used it to generate mice with conditional deletion of MHC class II(MHCII) molecules on cDC1s. By preventing cDC1s to receive suppressive regulatory T cell inputs via MHCII-restrictedinteractions, the objective of the present study was to gauge whether MHCII-deficient cDC1s lose their capacity oftolerizing autoreactive CD8+T cells. Whereas MHCII+cDC1 readily cross-tolerized strongly autoreactive CD8+T cellsspecific for a keratinocyte-derived self-antigen, MHCII-deficient cDC1s converted them into potent effectors capableof triggering a fast-onset lethal autoimmunity associated with severe skin histopathological manifestations. Preventingegress of such pathogenic self-reactive CD8+T cell effectors from the cutaneous draining lymph nodesabrogated the autoimmune condition. Therefore, our results revealed that the cross-tolerizing capacity of cDC1sis not a property fully acquired at the time they undergo homeostatic maturation but needs to be enforced viaMHCII-restricted, suppressive interactions with regulatory T cells.