An Optimized Protocol to Analyze Glycolysis and Mitochondrial Respiration in Lymphocytes

Lymphocytes respond to a variety of stimuli by activating intracellular signaling pathways, which in turn leads to rapid cellular proliferation, migration ...

National Institutes of Health

Paired receptors are groups of closely related membrane proteins that have the potential to either inhibit or activate. The CD200R family consists of one inhibitory member, CD200R and various numbers of activating genes according to species with three defined in C57BL/6 mice. A genomic PCR strategy was used to examine the repertoire of genes in both laboratory and wild-derived mice. Most mouse strains tested (18/22) had three activating genes, and 16 of these had either the combination of CD200RLa, Lb, and Lc or CD200RLa, Lb, and Le. The Lc and Le genes were mutually exclusive and were equally common (10 strains). Wild-derived mice varied more with one example of strains with one, two, and four activating genes. An inhibitory CD200R gene was detected in each mouse strain, although two slightly different sequences were found in both laboratory and wild-derived mice. This diversity is probably being driven by pathogens but is less extensive than for many NK paired receptors such as KIR and Ly49. It is possible that myeloid paired receptors are involved in immune regulation of responses against pathogens rather than directly killing infected cells as for NK cells and, hence, under less intense evolutionary pressure.

Heterogeneity in the CD200R paired receptor family.

Gene transfer into haematopoietic cells is a challenging approach. The extracellular matrix component fibronectin has been known to modulate the cell cycle dynamics, viability and differentiation of leukaemia cells. Thus, our aim was to investigate the influence of fibronectin substratum on the liposomal transfection of myeloid leukaemia cell lines. Liposomal transfection was performed with K562 and HL-60 as representative lines of transfection-competent and -incompetent myeloid leukaemia cells, respectively. Flow cytometry analyses were performed to determine transfection efficiency monitored by green fluorescent protein (GFP) expression and to assess cell viability and cell cycle status. Quantitation of GFP gene expression and DNA uptake was assayed by real time PCR. The current data showed that the adhesion to fibronectin deteriorated the transfection of K562 cells. In contrary, it enhanced the delivery of plasmid DNA into HL-60 cells. Correspondingly, the adhesion to fibronectin influenced the transfection efficiency mainly by modulating the intracellular presence of plasmid DNA. The cell cycle and viability which is regulated by fibronectin had a minor impact on the success of gene delivery. This phenomenon may be considered as an important factor which may modulate the potential gene transfer approaches for myeloid leukaemia.

Transfection of myeloid leukaemia cell lines is distinctively regulated by fibronectin substratum.

Paired receptors are families of membrane proteins characterized by similar extracellular regions but different transmembrane and cytoplasmic regions, meaning that some members can give inhibitory signals and others activating signals. Well-characterized examples include the KIR, SIRP, Ly49, Nkpr, and Siglec families. The difference in the repertoire of these genes in mouse and man indicates that these families have evolved rapidly. For example, KIRs are found in humans and not mice, and Ly49 shows the converse. These genes are often very polymorphic, e.g. KIR and the number of genes can vary as shown for Ly49 in different mouse strains. Paired receptors are expressed mainly on NK and myeloid cells and their evolution is thought to be pathogen driven. In this article, we review various receptor families for which pathogen interactions are known and discuss the possible molecular mechanisms driving their evolution.

How do pathogens drive the evolution of paired receptors?

The CD200 receptor (CD200R) is present mainly on myeloid cells and gives inhibitory signals when engaged by its ligand CD200. The interaction is currently of therapeutic interest in cancer and inflammation. However functional effects are complicated by the fact that CD200R is itself polymorphic and also a member of a paired receptor family with four closely related gene products in mice called CD200RLa etc. We show that a second allele of CD200R (termed CD200R(2)) that differs in 7 amino acids also binds CD200 but did not react with the widely used CD200R antibody OX110. Biochemical and functional analysis showed that the CD200/CD200R interaction was blocked by the OX131, mAb that recognises both CD200R(1) and CD200R(2), but not by OX110 mAb. Both mAb can give agonistic inhibitory signals but functional analysis shows OX131 mAb also has the potential to block inhibition by preventing the ligand-receptor interaction and hence gives opposing effects. Although OX131 mAb cross-reacts with the activating receptor CD200RLe, it is specific for CD200R in C57BL/6 whilst OX110 mAb cross-reacts on CD200RLc. The results show the importance of the repertoire of paired receptors in strains or individuals and mAb used with implications for paired receptor analysis and therapeutics.

Dissection of agonistic and blocking effects of CD200 receptor antibodies.

Malaria is an infectious disease caused by parasites of several Plasmodium spp. Cerebral malaria (CM) is a common form of severe malaria resulting in nearly 700,000 deaths each year in Africa alone. At present, there is no adjunctive therapy for CM. Although the mechanisms underlying the pathogenesis of CM are incompletely understood, it is likely that both intrinsic features of the parasite and the human host's immune response contribute to disease. The kinase mammalian target of rapamycin (mTOR) is a central regulator of immune responses, and drugs that inhibit the mTOR pathway have been shown to be antiparasitic. In a mouse model of CM, experimental CM (ECM), we show that the mTOR inhibitor rapamycin protects against ECM when administered within the first 4 days of infection. Treatment with rapamycin increased survival, blocked breakdown of the blood-brain barrier and brain hemorrhaging, decreased the influx of both CD4(+) and CD8(+) T cells into the brain and the accumulation of parasitized red blood cells in the brain. Rapamycin induced marked transcriptional changes in the brains of infected mice, and analysis of transcription profiles predicted that rapamycin blocked leukocyte trafficking to and proliferation in the brain. Remarkably, animals were protected against ECM even though rapamycin treatment significantly increased the inflammatory response induced by infection in both the brain and spleen. These results open a new avenue for the development of highly selective adjunctive therapies for CM by targeting pathways that regulate host and parasite metabolism.

Inhibiting the Mammalian target of rapamycin blocks the development of experimental cerebral malaria.

The most deadly complication of Plasmodium falciparum infection is cerebral malaria (CM) with a case fatality rate of 15-25% in African children despite effective antimalarial chemotherapy. There are no adjunctive treatments for CM, so there is an urgent need to identify new targets for therapy. Here we show that the glutamine analog 6-diazo-5-oxo-l-norleucine (DON) rescues mice from CM when administered late in the infection a time at which mice already are suffering blood-brain barrier dysfunction, brain swelling, and hemorrhaging accompanied by accumulation of parasite-specific CD8(+) effector T cells and infected red blood cells in the brain. Remarkably, within hours of DON treatment mice showed blood-brain barrier integrity, reduced brain swelling, decreased function of activated effector CD8(+) T cells in the brain, and levels of brain metabolites that resembled those in uninfected mice. These results suggest DON as a strong candidate for an effective adjunctive therapy for CM in African children.

Targeting glutamine metabolism rescues mice from late-stage cerebral malaria.

Several herpesviruses have acquired the gene for the CD200 membrane protein from their hosts and can downregulate myeloid activity through interaction of this viral CD200 orthologue with the host receptor for CD200, namely CD200R, which can give inhibitory signals. This receptor is a 'paired receptor', meaning proteins related to the inhibitory CD200R are present but differ in that they can give activating signals and also give a negligible interaction with CD200. We showed that the viral orthologues e127 from rat cytomegalovirus and K14 from human herpesvirus 8 do not bind the activating CD200R-like proteins from their respective species, although they do bind the inhibitory receptors. It is thought that the activating receptors have evolved in response to pathogens targeting the inhibitory receptor. In this case, the CD200 orthologue is not trapped by the activating receptor but has maintained the specificity of the host from which it was acquired, suggesting that the activating members of the CD200R family have evolved to protect against a different pathogen.

Herpesvirus orthologues of CD200 bind host CD200R but not related activating receptors.

CD200 is a widely distributed membrane protein that gives inhibitory signals through its receptor (CD200R) on myeloid cells. CD200 has been acquired by herpesviruses where it has been shown to interact with host CD200R and downmodulate the immune system. It has been hypothesized that poxviruses have acquired CD200; but the potential orthologues show less similarity to their hosts. Myxoma virus M141 protein is a potential CD200 orthologue with a potent immune modulatory function in rabbits. Here, we characterized the rabbit CD200, CD200R and tested the CD200-like sequences for binding CD200R. No binding could be detected using soluble recombinant proteins, full length protein expressed on cells or myxoma virus infected cells. Finally, using knockdown models, we showed that the inhibitory effect of M141 on RAW 264.7 cells upon myxoma virus infection is not due to CD200R. We conclude that the rabbit poxvirus CD200-like proteins cause immunomodulation without utilizing CD200R.

Rabbit CD200R binds host CD200 but not CD200-like proteins from poxviruses.

Barcoding of biological samples is a commonly used strategy to mark or identify individuals within a complex mixture. However, cell barcoding has not yet found wide use in flow cytometry that would benefit greatly from the ability to analyze pooled experimental samples simultaneously. This is due, in part, to technical and practical limitations of current fluorescent dye-based methods. In this study, we describe a simple, versatile barcoding strategy that relies on combinations of a single Ab conjugated to different fluorochromes and thus in principle can be integrated into any flow cytometry application. To demonstrate the efficacy of the approach, we describe the results of a variety of experiments using live cells as well as fixed and permeabilized cells. The results of these studies show that Ab-based barcoding provides a simple, practical method for identifying cells from individual samples pooled for analysis by flow cytometry that has broad applications in immunological research.

A Simple, Versatile Antibody-Based Barcoding Method for Flow Cytometry.

Plasmodium falciparum malaria is a deadly infectious disease in which Abs play a critical role in naturally acquired immunity. However, the specificity and nature of Abs elicited in response to malaria are only partially understood. Autoreactivity and polyreactivity are common features of Ab responses in several infections and were suggested to contribute to effective pathogen-specific Ab responses. In this article, we report on the regulation of B cells expressing the inherently autoreactive VH4-34 H chain (identified by the 9G4 mAb) and 9G4(+) plasma IgG in adults and children living in a P. falciparum malaria-endemic area in West Africa. The frequency of 9G4(+) peripheral blood CD19(+) B cells was similar in United States adults and African adults and children; however, more 9G4(+) B cells appeared in classical and atypical memory B cell compartments in African children and adults compared with United States adults. The levels of 9G4(+) IgG increased following acute febrile malaria but did not increase with age as humoral immunity is acquired or correlate with protection from acute disease. This was the case, even though a portion of 9G4(+) B cells acquired phenotypes of atypical and classical memory B cells and 9G4(+) IgG contained equivalent numbers of somatic hypermutations compared with all other VHs, a characteristic of secondary Ab repertoire diversification in response to Ag stimulation. Determining the origin and function of 9G4(+) B cells and 9G4(+) IgG in malaria may contribute to a better understanding of the varied roles of autoreactivity in infectious diseases.

Munir Akkaya

Laboratory of Immunogenetics,
National Institute of Allergy and Infectious Diseases,
Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases

National Institutes of Health

An Optimized Protocol to Analyze Glycolysis and Mitochondrial Respiration in Lymphocytes

Munir Akkaya

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Laboratory of Immunogenetics,National Institute of Allergy and Infectious Diseases,Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases

National Institutes of Health

An Optimized Protocol to Analyze Glycolysis and Mitochondrial Respiration in Lymphocytes

Laboratory of Immunogenetics,
National Institute of Allergy and Infectious Diseases,
Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases