Cells need to adapt to dynamic environments. Yeast that fail to cope with dynamic changes in the abundance of glucose can undergo growth arrest. We show that this failure is caused by imbalanced reactions in glycolysis, the essential pathway in energy metabolism in most organisms. The imbalance arises largely from the fundamental design of glycolysis, making this state of glycolysis a generic risk. Cells with unbalanced glycolysis coexisted with vital cells. Spontaneous, nongenetic metabolic variability among individual cells determines which state is reached and, consequently, which cells survive. Transient ATP (adenosine 5'-triphosphate) hydrolysis through futile cycling reduces the probability of reaching the imbalanced state. Our results reveal dynamic behavior of glycolysis and indicate that cell fate can be determined by heterogeneity purely at the metabolic level.

The impact of the nutritional status during foetal life in the overall health of adults has been recognised1. However dietary effects on the developing immune system are largely unknown. Development of secondary lymphoid organs (SLOs) occurs during embryogenesis and is considered to be developmentally programmed2,3. SLO formation dependents on a subset of type 3 innate lymphoid cells (ILC3) named lymphoid tissue inducer (LTi) cells2,3,4,5. Here we show that foetal ILC3s are controlled by cell-autonomous retinoic acid (RA) signalling in utero pre-setting the immune fitness in adulthood. We found that embryonic lymphoid organs contain ILC progenitors that differentiate locally into mature LTi cells. Local LTi differentiation was controlled by maternal retinoid intake and foetal RA signalling acting in a haematopoietic cell-autonomous manner. RA controlled LTi cell maturation upstream of the transcription factor RORγt. Accordingly, enforced expression of Rorgt restored maturation of LTi cells with impaired RA signalling, while RA receptors directly regulated the Rorc locus. Finally, we established that maternal levels of dietary retinoids control the size of secondary lymphoid organs and the efficiency of immune responses in the adult offspring. Our results reveal a molecular link between maternal nutrients and the formation of immune structures required for resistance to infection in the offspring.

The spleen is the lymphoid organ that induces immune responses toward blood-borne pathogens. Specialized macrophages in the splenic marginal zone are strategically positioned to phagocytose pathogens and cell debris, but are not known to play a role in the activation of T-cell responses. Here we demonstrate that splenic marginal metallophilic macrophages (MMM) are essential for crosspresentation of blood-borne antigens by splenic dendritic cells (DCs). Our data demonstrate that antigens targeted to MMM as well as blood-borne adenoviruses are efficiently captured by MMM and exclusively transferred to splenic CD8 + DCs for cross-presentation and for the activation of cytotoxic T lymphocytes. Depletion of macrophages in the marginal zone prevents cytotoxic T-lymphocyte activation by CD8 + DCs after antibody targeting or adenovirus infection. Moreover, we show that tumor antigen targeting to MMM is very effective as antitumor immunotherapy. Our studies point to an important role for splenic MMM in the initial steps of CD8 + T-cell immunity by capturing and concentrating blood-borne antigens and the transfer to cross-presenting DCs which can be used to design vaccination strategies to induce antitumor cytotoxic T-cell immunity.antigen presentation | infection T he spleen is essential for the induction of immune responses toward blood-borne antigens and has a unique architecture. Arterial blood flow terminates in marginal sinuses situated in the marginal zone (MZ) that surrounds the white pulp containing Bcell follicles and T-cell zones. Marginal sinuses are lined by reticular cells and contain marginal zone B cells and two types of macrophages (Mφ) (1, 2). Marginal metallophilic macrophages (MMM), characterized by the expression of sialic acid-binding Iglike lectin-1 (Siglec-1, Sialoadhesin, CD169) (3, 4), are located as a tight network in the inner part of the MZ near the white pulp, whereas marginal zone macrophages (MZM), which specifically express the C-type lectin SIGN-R1, can be found in the outer MZ toward the red pulp (5). Both MZM and a subset of MMM express the type I scavenger receptor MARCO (6). Although MMM and MZM efficiently take up particulate antigens (Ag) present in the blood (7-9), they are hitherto considered not to be important for the generation of T-cell responses (8-10).In contrast to Mφ, dendritic cells (DCs) are specialized Agpresenting cells that have a dominant role in initiating primary Tcell responses. Murine splenic DCs can be divided into two different subsets based on the expression of phenotypic markers: localization and function (11). CD8 + DCs express the C-type lectin DEC205 and are found in the T-cell zone and the outer marginal zone (12). They are specialized in cross-presentation of Ag and in the activation and tolerization of cytotoxic T cells (CTLs) (13-16). Furthermore, they are important for the generation of antitumor specific immune responses and the elimination of tumors in vivo (17). In contrast, CD8− DCs are specialized in the activation of CD4 + T cells. CD8 − DCs are...

The vitamin A metabolite retinoic acid (RA) plays a crucial role in mucosal immune responses. We demonstrate in this study that RA-producing retinaldehyde dehydrogenase (RALDH) enzymes are postnatally induced in mesenteric lymph node (MLN) dendritic cells (DCs) and MLN stromal cells. RALDH enzyme activity in lamina propria-derived CD103+ MLN-DCs did not depend on TLR signaling. Remarkably, RA itself could directly induce RALDH2 in both DCs and stromal cells in vitro. Furthermore, upon provision of a vitamin A-deficient diet, it was found that RA-mediated signaling was strongly reduced within the small intestines, while RALDH2 mRNA and RALDH enzyme activity in lamina propria DCs and MLN-DCs, as well as RALDH2 mRNA expression in MLN stromal cells, were strongly diminished. Moreover, supply of vitamin A to vitamin A-deficient mice restored RA-mediated signaling in the intestine and RALDH activity in lamina propria-derived CD103+ MLN-DCs. Our results show that RA-dependent signaling within the intestine is indispensable for RALDH activity in the draining MLN.

The DNA array technique allows comprehensive analysis of the genome and transcriptome, but the high throughput array-based assessment of intracellular signal transduction remains troublesome. The goal of this study was to test a new peptide array technology for studying the activity of all kinases of whole cell lysates, the kinome. Cell lysates from human peripheral blood mononuclear cells before and after stimulation with lipopolysaccharide were used for in vitro phosphorylation with [␥-33 P]ATP arrays consisting of 192 peptides (substrates for kinases) spotted on glass. The usefulness of peptide arrays for studying signal transduction was demonstrated by the generation of the first comprehensive description of the temporal kinetics of phosphorylation events induced by lipopolysaccharide stimulation. Furthermore analysis of the signals obtained suggested activation of p21Ras by lipopolysaccharide, and this was confirmed by direct measurement of p21Ras GTP levels in lipopolysaccharide-stimulated human peripheral blood mononuclear cells, which represents the first direct demonstration of p21Ras activation by stimulation of a Toll receptor family member. Further confidence in the usefulness of peptide array technology for studying signal transduction came from Western blot analysis of lipopolysaccharide-stimulated cells, which corroborated the signals obtained using peptide arrays as well as from the demonstration that kinase inhibitors effected peptide array phosphorylation patterns consistent with the expected action of these inhibitors. We conclude that this first metabolic array is a useful method to determine the enzymatic activities of a large group of kinases, offering high throughput analysis of cellular metabolism and signal transduction.Massive parallel analysis using array technology has become the mainstay for the analysis of genomes and transcriptomes (1-5). Since the determination of the transcriptome, the understanding of cellular functioning has improved dramatically. Novel insights have led to the notion that the majority of the transcriptome is necessary to keep a cell functioning and could be regarded as the minimal transcriptome. Only a small portion of the transcripts present in the cell determines the identity of the cell, and these critical transcripts are expressed at low levels. Therefore small changes in the expression profiles in the transcriptome can lead to large changes in enzymatic profile of the cell leading to significant differences in cell functioning (6). Thus, a comprehensive description of cellular metabolism may be more useful than such a description of the genome and transcriptome.Array technology has not yet been adapted to measure enzymatic activity in whole cell lysates, but progress has been made with the preparation of protein chips for the assessment of protein substrate interactions (7-10) and the generation of peptide chips for the appraisal of ligand-receptor interactions and enzymatic activities (11-13). Recently Houseman and Mrksich (14) showed that employing pept...