Phosphatidic acid and tumor necrosis factor-alpha induce the expression of CD83 through mitogen activated protein kinase pathway in a CD34+ hematopoietic progenitor cell line, KG1

Hematopoietic stem and progenitor cells confer cross-protective trained immunity in mouse models

Recent studies suggest that infection reprograms hematopoietic stem and progenitor cells (HSPCs) to enhance innate immune responses upon secondary infectious challenge, a process called "trained immunity." However, the specificity and cell types responsible for this response remain poorly defined. We established a model of trained immunity in mice in response to Mycobacterium avium infection. scRNA-seq analysis revealed that HSPCs activate interferon gamma-response genes heterogeneously upon primary challenge, while rare cell populations expand. Macrophages derived from trained HSPCs demonstrated enhanced bacterial killing and metabolism, and a single dose of recombinant interferon gamma exposure was sufficient to induce similar training. Mice transplanted with influenza-trained HSPCs displayed enhanced immunity against M. avium challenge and vice versa, demonstrating cross protection against antigenically distinct pathogens. Together, these results indicate that heterogeneous responses to infection by HSPCs can lead to long-term production of bone marrow derived macrophages with enhanced function and confer cross-protection against alternative pathogens.

Gene expression profiling and network analysis of peripheral blood monocytes in a chronic model of allergic asthma

The Aspergillus fumigatus mouse model of asthma mimics the characteristics of human fungal asthma, including local and systemic inflammation. Monocyte/macrophage lineage cells direct innate immune responses and guide adaptive responses. To identify gene expression changes in peripheral blood monocytes in the context of fungal allergy, mice were exposed to systemic and intranasal inoculations of fungal antigen (sensitized), and naïve and sensitized animals were challenged intratracheally with live A. fumigatus conidia. Microarray analysis of blood monocytes from allergic versus non-allergic mice showed ≥ twofold modulation of 45 genes. Ingenuity pathway analysis revealed a network of these genes involved in antigen presentation, inflammation, and immune cell trafficking. These data show that allergen sensitization and challenge affects gene expression in peripheral monocytes.

Dissection of a complex transcriptional response using genome-wide transcriptional modelling

Modern genomics technologies generate huge data sets creating a demand for systems level, experimentally verified, analysis techniques. We examined the transcriptional response to DNA damage in a human T cell line (MOLT4) using microarrays. By measuring both mRNA accumulation and degradation over a short time course, we were able to construct a mechanistic model of the transcriptional response. The model predicted three dominant transcriptional activity profiles—an early response controlled by NFκB and c-Jun, a delayed response controlled by p53, and a late response related to cell cycle re-entry. The method also identified, with defined confidence limits, the transcriptional targets associated with each activity. Experimental inhibition of NFκB, c-Jun and p53 confirmed that target predictions were accurate. Model predictions directly explained 70% of the 200 most significantly upregulated genes in the DNA-damage response. Genome-wide transcriptional modelling (GWTM) requires no prior knowledge of either transcription factors or their targets. GWTM is an economical and effective method for identifying the main transcriptional activators in a complex response and confidently predicting their targets.

Phosphatidic acid induces the differentiation of human acute promyelocytic leukemic cells into dendritic cell-like

We investigated whether phosphatidic acid (PA) can differentiate the promyelocytic leukemia (PML)-retinoic acid receptor alpha (RAR alpha)-expressing acute promyelocytic leukemic cell line, NB4, to dendritic cell (DC)-like cells. Dioctanoyl-PA alone upregulated the expression of DC markers. The expression of DC markers on NB4 cells was potentiated by the overexpression of phospholipase D and upregulation was blocked by the addition of n-butanol, an inhibitor of PA production. The expression of CD11c, CD83, and CCR7 in PA-treated NB4 cells was further increased by tumor necrosis factor (TNF)-alpha treatment. Increased functional capacities were also found in PA-differentiated and TNF-alpha-activated NB4 cells with respect to changes in T-cell proliferation, cytokine production, endocytic activity, and cytolytic capacity against undifferentiated NB4 cells. PA alone increased the phosphorylation of extracellular signal-regulated kinase (ERK)-1/2. The expression of DC markers was downregulated by PD98059, a specific inhibitor of ERK kinase or transient transfection of mutant-ERK. The level of PML-RAR alpha fusion protein was decreased by PA treatment and PD98059 blocked the decrease of PML-RAR alpha. These results suggest that PA induces differentiation of NB4 cells into DC-like cells and that the upregulation of antigen presenting cell markers is mediated by the activation of ERK and the downregulation of PML-RAR alpha levels.