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bB cell differentiation into antibody-secreting cells (ASCs) is a tightly regulated process under the control of multiple transcription factors. One such transcription factor, Ets1, blocks the transition of B cells to ASCs via two separate activities: (i) stimulating the expression of target genes that promote B cell identity and (ii) interfering with the functional activity of the transcription factor Blimp1. Ets1 is a member of a multigene family, several members of which are expressed within the B cell lineage, including the closely related protein Ets2. In this report, we demonstrate that Ets1, but not Ets2, can block ASC formation despite the fact that Ets1 and Ets2 bind to apparently identical DNA sequence motifs and are thought to regulate overlapping sets of target genes. The DNA binding domain of Ets1 is required, but not sufficient by itself, to block ASC formation. In addition, less conserved regions within the N terminus of Ets1 play an important role in inhibiting B cell differentiation. Differences between the N termini of Ets1 and Ets2, rather than differences in the DNA binding domains, determine whether the proteins are capable of blocking ASC formation or not.

SummaryThe transcription factor Ets1 is normally expressed in the proliferative layer of stratified epithelium, but expression of Ets1 is significantly upregulated in squamous cell carcinomas. How elevated levels of Ets1 impact tumor initiation and progression is not well understood. To determine the biological consequences of overexpression of Ets1, we developed a transgenic mouse model that allows induction of Ets1 expression in keratinocytes of stratified epithelium in a regulatable fashion. Induction of Ets1 during embryonic development results in a dramatic alteration in epidermal structure and function by suppressing the expression of multiple stratum corneum constituents, while at the same time inducing expression of EGF ligands, AP1 transcription factors and matrix metalloproteases. Interestingly, expression of certain immune-related genes, including defensins, chemokines and cytokines was increased as well, suggesting a possible role for immune dysregulation in the promotion of squamous dysplasia. Experiments using cultured mouse keratinocytes indicate that Ets1 can induce expression of some of these mediators in a cell-intrinsic fashion. Collectively, our data reveal that elevated expression of Ets1 has a much broader array of pro-tumorigenic effects on epithelial cells than previously appreciated.

Recent findings have revealed roles for systemic and mucosal-resident memory CD8+ T cells in the orchestration of innate immune responses critical to host defense upon microbial infection. Here we integrate these findings into the current understanding of the molecular and cellular signals controlling memory CD8+ T cell reactivation, and the mechanisms by which these cells mediate effective protection in vivo. The picture that emerges presents memory CD8+ T cells as early sensors of danger signals, mediating protective immunity both through licensing of cellular effectors of the innate immune system and via the canonical functions associated with memory T cells. We discuss implications to the development of T cell vaccines and therapies, and highlight important areas in need of further investigation.

Foxp3+CD4+ regulatory T (Treg) cells are essential for preventing fatal autoimmunity and safeguard immune homeostasis in vivo. While expression of the transcription factor Foxp3 and IL-2 signals are both required for the development and function of Treg cells, the commitment to the Treg cell lineage occurs during thymic selection upon T cell receptor (TCR) triggering, and precedes the expression of Foxp3. Whether signals beside TCR contribute to establish Treg cell epigenetic and functional identity is still unknown. Here, using a mouse model with reduced IL-2 signaling, we show that IL-2 regulates the positioning of the pioneer factor SATB1 in CD4+ thymocytes and controls genome wide chromatin accessibility of thymic-derived Treg cells. We also show that Treg cells receiving only low IL-2 signals can suppress endogenous but not WT autoreactive T cell responses in vitro and in vivo. Our findings have broad implications for potential therapeutic strategies to reprogram Treg cells in vivo.