Multi-transcription factor reporter mice delineate early precursors to the ILC and LTi lineages

Transcription factor (TF) reporter mice have proved integral to the characterization of murine innate lymphoid cell (ILC) development and function. Here, we implemented a CRISPR/Cas9-generated combinatorial reporter approach for the simultaneous resolution of several key TFs throughout ILC development in both the fetal liver and adult bone marrow. We demonstrate that the Tcf7-expressing early innate lymphoid precursor (EILP) and the common helper ILC precursor (CHILP) both contain a heterogeneous mixture of specified ILC and lymphoid tissue inducer (LTi) precursors with restricted lineage potential rather than a shared precursor. Moreover, the earliest specified precursor to the LTi lineage was identified upstream of these populations, before Tcf7 expression. These findings match dynamic changes in chromatin accessibility associated with the expression of key TFs (i.e., GATA3 and RORγ(t)), highlighting the distinct origins of ILC and LTi lineages at the epigenetic and functional levels, and provide a revised map for ILC development

A shared Runx1-bound <i>Zbtb16</i> enhancer directs innate and innate-like lymphoid lineage development

Zbtb16-encoded PLZF is a signature transcription factor (TF) that directs the acquisition of T-helper effector programs during the development of multiple innate lymphocyte lineages, including natural killer T cell, innate lymphoid cell, mucosal-associated invariant T cell and γδ lineages. PLZF is also essential in osteoblast and spermatogonial development. How Zbtb16 itself is regulated in different lineages is incompletely understood. Here, by systematic CRISPR/Cas9-assisted deletions of chromatin accessible regions within the Zbtb16 locus in mouse, we identify a critical enhancer controlling PLZF expression exclusively in innate lymphoid lineages. Multiple sites within this enhancer express canonical motifs for the TF Runx1, which is essential for the development of these lineages. Notably, some regulatory sites control the kinetic rather than the overall level of PLZF expression. Thus, our comprehensive, unbiased analysis of regulatory elements in vivo reveals critical mechanisms of Zbtb16 regulation shared between innate and innate-like lymphoid lineages

Dendritic cells can prime anti-tumor CD8+ T cell responses through major histocompatibility complex cross-dressing

Antigen cross-presentation, wherein dendritic cells (DCs) present exogenous antigen on major histocompatibility class I (MHC-I) molecules, is considered the primary mechanism by which DCs initiate tumor-specific CD8+ T cell responses. Here, we demonstrate that MHC-I cross-dressing, an antigen presentation pathway in which DCs acquire and display intact tumor-derived peptide:MHC-I molecules, is also important in orchestrating anti-tumor immunity. Cancer cell MHC-I expression was required for optimal CD8+ T cell activation in two subcutaneous tumor models. In vivo acquisition of tumor-derived peptide:MHC-I molecules by DCs was sufficient to induce antigen-specific CD8+ T cell priming. Transfer of tumor-derived human leukocyte antigen (HLA) molecules to myeloid cells was detected in vitro and in human tumor xenografts. In conclusion, MHC-I cross-dressing is crucial for anti-tumor CD8+ T cell priming by DCs. In addition to quantitatively enhancing tumor antigen presentation, MHC cross-dressing might also enable DCs to more faithfully and efficiently mirror the cancer cell peptidome