Sharline Madera

The Transcription Factors T-bet and Eomes Control Key Checkpoints of Natural Killer Cell Maturation

Natural killer (NK) cells play critical roles defending against tumors and pathogens. We show that mice lacking both transcription factors Eomesodermin (Eomes) and T-bet failed to develop NK cells. Developmental stability of immature NK cells constitutively expressing the death ligand TRAIL depended on T-bet. Conversely, maturation characterized by loss of constitutive TRAIL expression and induction of Ly49 receptor diversity and integrin CD49b (DX5(+)) required Eomes. Mature NK cells from which Eomes was deleted reverted to phenotypic immaturity if T-bet was present or downregulated NK lineage antigens if T-bet was absent, despite retaining expression of Ly49 receptors. Fetal and adult hepatic hematopoiesis restricted Eomes expression and limited NK development to the T-bet-dependent, immature stage, whereas medullary hematopoiesis permitted Eomes-dependent NK maturation in adult mice. These findings reveal two sequential, genetically separable checkpoints of NK cell maturation, the progression of which is metered largely by the anatomic localization of hematopoiesis.

Proinflammatory cytokine signaling required for the generation of natural killer cell memory

Responsiveness to interleukin-12, but not interferon-γ, is essential for the generation of long-lived natural killer cells capable of responding to secondary viral infection.

Nfil3-independent lineage maintenance and antiviral response of natural killer cells

Inflammatory cytokines drive NK cell expansion in the absence of the transcription factor Nfil3, and Nfil3 is dispensable for the maintenance and function of mature NK cells.

Proapoptotic Bim regulates antigen-specific NK cell contraction and the generation of the memory NK cell pool after cytomegalovirus infection

NK cells lacking proapoptotic factor Bim show impaired contraction phase after MCMV infection, leading to impaired memory cell maturation and a less effective responses to viral rechallenge.

Cutting Edge: Stage-Specific Requirement of IL-18 for Antiviral NK Cell Expansion

Although NK cells are considered part of the innate immune system, recent studies have demonstrated the ability of Ag-experienced NK cells to become long-lived and contribute to potent recall responses similar to T and B cells. The precise signals that promote the generation of a long-lived NK cell response are largely undefined. In this article, we demonstrate that NK cells require IL-18 signaling to generate a robust primary response during mouse CMV (MCMV) infection but do not require this signal for memory cell maintenance or recall responses. IL-12 signaling and STAT4 in activated NK cells increased the expression of the adaptor protein MyD88, which mediates signaling downstream of the IL-18 and IL-1 receptors. During MCMV infection, NK cells required MyD88, but not IL-1R, for optimal expansion. Thus, an IL-18–MyD88 signaling axis facilitates the prolific expansion of NK cells in response to primary viral infection, but not recall responses.

Cutting Edge: Divergent Requirement of T-Box Transcription Factors in Effector and Memory NK Cells

The T-box transcription factors T-bet and Eomesodermin (Eomes) instruct discrete stages in NK cell development. However, their role in the immune response of mature NK cells against pathogens remains unexplored. We used an inducible deletion system to elucidate the cell-intrinsic role of T-bet and Eomes in mature NK cells during the course of mouse CMV infection. We show both T-bet and Eomes to be necessary for the expansion of virus-specific NK cells, with T-bet upregulation induced by IL-12 signaling and STAT4 binding to a conserved enhancer region upstream of the Tbx21 loci. Interestingly, our data suggest maintenance of virus-specific memory NK cell numbers and phenotype was dependent on T-bet, but not Eomes. These findings uncover a nonredundant and stage-specific influence of T-box transcription factors in the antiviral NK cell response.

Exploring intentions of physician-scientist trainees: factors influencing MD and MD/PhD interest in research careers

BackgroundPrior studies have described the career paths of physician-scientist candidates after graduation, but the factors that influence career choices at the candidate stage remain unclear. Additionally, previous work has focused on MD/PhDs, despite many physician-scientists being MDs. This study sought to identify career sector intentions, important factors in career selection, and experienced and predicted obstacles to career success that influence the career choices of MD candidates, MD candidates with research-intense career intentions (MD-RI), and MD/PhD candidates.MethodsA 70-question survey was administered to students at 5 academic medical centers with Medical Scientist Training Programs (MSTPs) and Clinical and Translational Science Awards (CTSA) from the NIH. Data were analyzed using bivariate or multivariate analyses.ResultsMore MD/PhD and MD-RI candidates anticipated or had experienced obstacles related to balancing academic and family responsibilities and to balancing clinical, research, and education responsibilities, whereas more MD candidates indicated experienced and predicted obstacles related to loan repayment. MD/PhD candidates expressed higher interest in basic and translational research compared to MD-RI candidates, who indicated more interest in clinical research. Overall, MD-RI candidates displayed a profile distinct from both MD/PhD and MD candidates.ConclusionsMD/PhD and MD-RI candidates experience obstacles that influence their intentions to pursue academic medical careers from the earliest training stage, obstacles which differ from those of their MD peers. The differences between the aspirations of and challenges facing MD, MD-RI and MD/PhD candidates present opportunities for training programs to target curricula and support services to ensure the career development of successful physician-scientists.

Molecular Programming of Immunological Memory in Natural Killer Cells.

Immunological memory is a hallmark of the adaptive immune system. Although natural killer (NK) cells have traditionally been classified as a component of the innate immune system, they have recently been shown in mice and humans to exhibit certain features of immunological memory, including an ability to undergo a clonal-like expansion during virus infection, generate long-lived progeny (i.e. memory cells), and mediate recall responses against previously encountered pathogens--all characteristics previously ascribed only to adaptive immune responses by B and T cells in mammals. To date, the molecular events that govern the generation of NK cell memory are not completely understood. Using a mouse model of cytomegalovirus infection, we demonstrate that individual pro-inflammatory IL-12, IL-18, and type I-IFN signaling pathways are indispensible and play non-redundant roles in the generation of virus-specific NK cell memory. Furthermore, we discovered that antigen-specific proliferation and protection by NK cells is mediated by the transcription factor Zbtb32, which is induced by pro-inflammatory cytokines and promotes a cell cycle program in activated NK cells. A greater understanding of the molecular mechanisms controlling NK cell responses will provide novel strategies for tailoring vaccines to target infectious disease.