scholarly journals Diversity of immune strategies explained by adaptation to pathogen statistics

2015 ◽  
Author(s):  
Andreas Mayer ◽  
Thierry Mora ◽  
Olivier Rivoire ◽  
Aleksandra M Walczak
Keyword(s):  
Mathematical Framework ◽  
Bet Hedging ◽  
Term Survival ◽  
Immune Systems ◽  
Immune Mechanisms ◽  
Pathogen Dynamics ◽  
Wide Range ◽  
Two Parameters ◽  
Biological Organisms

Biological organisms have evolved a wide range of immune mechanisms to defend themselves against pathogens. Beyond molecular details, these mechanisms differ in how protection is acquired, processed and passed on to subsequent generations -- differences that may be essential to long-term survival. Here, we introduce a mathematical framework to compare the long-term adaptation of populations as a function of the pathogen dynamics that they experience and of the immune strategy that they adopt. We find that the two key determinants of an optimal immune strategy are the frequency and the characteristic timescale of the pathogens. Depending on these two parameters, our framework identifies distinct modes of immunity, including adaptive, innate, bet-hedging and CRISPR-like immunities, which recapitulate the diversity of natural immune systems.

scholarly journals Diversity of immune strategies explained by adaptation to pathogen statistics

2016 ◽  
Vol 113 (31) ◽  
pp. 8630-8635 ◽  
Author(s):  
Andreas Mayer ◽  
Thierry Mora ◽  
Olivier Rivoire ◽  
Aleksandra M. Walczak
Keyword(s):  
Mathematical Framework ◽  
Bet Hedging ◽  
Term Survival ◽  
Immune Systems ◽  
Immune Mechanisms ◽  
Pathogen Dynamics ◽  
Wide Range ◽  
Two Parameters ◽  
Biological Organisms

Biological organisms have evolved a wide range of immune mechanisms to defend themselves against pathogens. Beyond molecular details, these mechanisms differ in how protection is acquired, processed, and passed on to subsequent generations—differences that may be essential to long-term survival. Here, we introduce a mathematical framework to compare the long-term adaptation of populations as a function of the pathogen dynamics that they experience and of the immune strategy that they adopt. We find that the two key determinants of an optimal immune strategy are the frequency and the characteristic timescale of the pathogens. Depending on these two parameters, our framework identifies distinct modes of immunity, including adaptive, innate, bet-hedging, and CRISPR-like immunities, which recapitulate the diversity of natural immune systems.

scholarly journals From young massive star clusters to old globulars: long-term survival chances

2006 ◽  
Vol 2 (S237) ◽  
pp. 408-408
Author(s):  
Richard de Grijs
Keyword(s):  
Galaxy Formation ◽  
Massive Star ◽  
Cluster Formation ◽  
Star Clusters ◽  
Term Survival ◽  
Star Forming ◽  
Distant Galaxies ◽  
Wide Range ◽  
Galaxy Collisions

Young, massive star clusters (YMCs) are the most notable and significant end products of violent star-forming episodes triggered by galaxy collisions and close encounters. The question remains, however, whether or not at least a fraction of the compact YMCs seen in abundance in extragalactic starbursts, are potentially the progenitors of (≳10 Gyr) old globular cluster (GC)-type objects. If we could settle this issue convincingly, one way or the other, the implications of such a result would have far-reaching implications for a wide range of astrophysical questions, including our understanding of the process of galaxy formation and assembly, and the process and conditions required for star (cluster) formation. Because of the lack of a statistically significant sample of YMCs in the Local Group, however, we need to resort to either statistical arguments or to the painstaking approach of case-by-case studies of individual objects in more distant galaxies.

scholarly journals Constitutive expression of bcl-2 in B cells causes a lethal form of lupuslike autoimmune disease after induction of neonatal tolerance to H-2b alloantigens.

1996 ◽  
Vol 183 (6) ◽  
pp. 2523-2531 ◽  
Author(s):  
M López-Hoyos ◽  
R Carrió ◽  
R Merino ◽  
L Buelta ◽  
S Izui ◽  
...  
Keyword(s):  
B Cells ◽  
Autoimmune Disease ◽  
Constitutive Expression ◽  
Systemic Autoimmune Disease ◽  
Spleen Cells ◽  
Term Survival ◽  
F1 Hybrid ◽  
Wide Range

The bcl-2 protooncogene has been shown to provide a survival signal to self-reactive B cells, but it fails to override their developmental arrest after encounter with antigen. Furthermore, constitutive expression of bcl-2 in B cells does not promote the development of autoimmune disease in most strains of mice, indicating that signals other than those conferred by bcl-2 are required for long-term survival and differentiation of self-reactive B cells in vivo. To further examine the factors that are required for the pathogenesis of autoimmune disease, we have assessed the effect of bcl-2 overexpression on the development of host-versus-graft disease, a self-limited model of systemic autoimmune disease. In this model, injection of spleen cells from (C57BL/6 x BALB/c)F1 hybrid mice into BALB/c newborn parental mice induces immunological tolerance to donor tissues and activation of autoreactive F1 donor B cells through interactions provided by allogeneic host CD4+ T cells. BALB/c newborns injected with spleen cells from (C57BL/6 x BALB/c)F1 mice expressing a bcl-2 transgene in B cells developed high levels of anti-single-stranded DNA and a wide range of pathogenic autoantibodies that were not or barely detectable in mice injected with nontransgenic spleen cells. In mice injected with transgenic B cells, the levels of pathogenic autoantibodies remained high during the course of the study and were associated with long-term persistence of donor B cells, development of a severe autoimmune disease, and accelerated mortality. These results demonstrate that bcl-2 can provide survival signals for the maintenance and differentiation of autoreactive B cells, and suggest that both increased B cell survival and T cell help play critical roles in the development of certain forms of systemic autoimmune disease.

scholarly journals Epidemiology and long-term outcome in outpatients with chronic heart failure in Northwestern Europe

Heart ◽  
2019 ◽  
Vol 105 (16) ◽  
pp. 1252-1259 ◽  
Author(s):  
Hanna Fröhlich ◽  
Niklas Rosenfeld ◽  
Tobias Täger ◽  
Kevin Goode ◽  
Syed Kazmi ◽  
...  
Keyword(s):  
Heart Failure ◽  
Chronic Heart Failure ◽  
Ejection Fraction ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Term Survival ◽  
Period 2 ◽  
Wide Range ◽  
Ambulatory Patients

ObjectiveTo describe the epidemiology, long-term outcomes and temporal trends in mortality in ambulatory patients with chronic heart failure (HF) with reduced (HFrEF), mid-range (HFmrEF) or preserved ejection fraction (HFpEF) from three European countries.MethodsWe identified 10 312 patients from the Norwegian HF Registry and the HF registries of the universities of Heidelberg, Germany, and Hull, UK. Patients were classified according to baseline left ventricular ejection fraction (LVEF) and time of enrolment (period 1: 1995–2005 vs period 2: 2006–2015). Predictors of mortality were analysed by use of univariable and multivariable Cox regression analyses.ResultsAmong 10 312 patients with stable HF, 7080 (68.7%), 2086 (20.2%) and 1146 (11.1%) were classified as having HFrEF, HFmrEF or HFpEF, respectively. A total of 4617 (44.8%) patients were included in period 1, and 5695 (55.2%) patients were included in period 2. Baseline characteristics significantly differed with respect to type of HF and time of enrolment. During a median follow-up of 66 (33–105) months, 5297 patients (51.4%) died. In multivariable analyses, survival was independent of LVEF category (p>0.05), while mortality was lower in period 2 as compared with period 1 (HR 0.81, 95% CI 0.72 to 0.91, p<0.001). Significant predictors of all-cause mortality regardless of HF category were increasing age, New York Heart Association functional class, N-terminal pro-brain natriuretic peptide and use of loop diuretics.ConclusionAmbulatory patients with HF stratified by LVEF represent different phenotypes. However, after adjusting for a wide range of covariates, long-term survival is independent of LVEF category. Outcome significantly improved during the last two decades irrespective from type of HF.

scholarly journals Survival of and In Situ Gene Expression by Vibrio vulnificus at Varying Salinities in Estuarine Environments

2007 ◽  
Vol 74 (1) ◽  
pp. 182-187 ◽  
Author(s):  
Melissa K. Jones ◽  
Elizabeth Warner ◽  
James D. Oliver
Keyword(s):  
Gene Expression ◽  
Vibrio Vulnificus ◽  
Natural Habitat ◽  
Term Survival ◽  
Long Term Survival ◽  
Wide Range ◽  
Opportunistic Human Pathogen

ABSTRACT The opportunistic human pathogen Vibrio vulnificus survives in a wide range of ecological environments, which demonstrates its ability to adapt to highly variable conditions. Survival and gene expression under various conditions have been extensively studied in vitro; however, little work has been done to evaluate this bacterium in its natural habitat. Therefore, this study monitored the long-term survival of V. vulnificus in situ and simultaneously evaluated the expression of stress (rpoS, relA, hfq, and groEL) and putative virulence (vvpE, smcR, viuB, and trkA) genes at estuarine sites of varying salinity. Additionally, the survival and gene expression of an rpoS and an oxyR mutant were examined under the same conditions. Differences between the sampling sites in the long-term survival of any strain were not seen. However, differences were seen in the expression of viuB, trkA, and relA but our findings differed from what has been previously shown in vitro. These results also routinely demonstrated that genes required for survival under in vitro stress or host conditions are not necessarily required for survival in the water column. Overall, this study highlights the need for further in situ evaluation of this bacterium in order to gain a true understanding of its ecology and how it relates to its natural habitat.

Effect of Revascularization on Long-Term Survival in Patients With Ischemic Left Ventricular Dysfunction and a Wide Range of Viability

2010 ◽  
Vol 106 (2) ◽  
pp. 187-192 ◽  
Author(s):  
Stephen G. Sawada ◽  
Saumyadip Dasgupta ◽  
James Nguyen ◽  
Kathleen A. Lane ◽  
Irmina Gradus-Pizlo ◽  
...  
Keyword(s):  
Left Ventricular Dysfunction ◽  
Ventricular Dysfunction ◽  
Left Ventricular ◽  
Term Survival ◽  
Long Term Survival ◽  
Wide Range

scholarly journals Evolutionary rescue through partly heritable phenotypic variability

2016 ◽  
Author(s):  
Oana Carja ◽  
Joshua B. Plotkin
Keyword(s):  
Genetic Model ◽  
Phenotypic Variability ◽  
Population Persistence ◽  
Single Individual ◽  
Bet Hedging ◽  
Term Survival ◽  
Direct Benefit ◽  
Evolutionary Rescue ◽  
The Mean

AbstractEnvironmental variation is commonplace, but unpredictable. Populations that encounter a deleterious environment can sometimes avoid extinction by rapid evolutionary adaptation. Phenotypic variability, whereby a single genotype can express multiple different phenotypes, might play an important role in rescuing such populations from extinction. This type of evolutionary bet-hedging need not confer a direct benefit to a single individual, but it may increase the chance of long-term survival of a lineage. Here we develop a population-genetic model to explore how partly heritable phenotypic variability influences the probability of evolutionary rescue and the mean duration of population persistence in changing environments. We find that the probability of population persistence depends non-monotonically on the degree of phenotypic heritability between generations: some heritability can help avert extinction, but too much heritability removes any benefit of phenotypic variability. We discuss the implications of these results in the context of therapies designed to eradicate populations of pathogens or aberrant cellular lineages.

scholarly journals Density of Nocturnal Mammals in a Forest Patch in Bangladesh

2020 ◽  
Author(s):  
Hassan Al-Razi ◽  
Sabit Hasan ◽  
Tanvir Ahmed ◽  
Sabir Bin Muzaffar
Keyword(s):  
Distance Sampling ◽  
Apex Predators ◽  
Slow Loris ◽  
Forest Patch ◽  
Term Survival ◽  
Wide Range ◽  
The Common ◽  
Nocturnal Mammals ◽  
Severe Disturbance

Tropical forests harbor complex communities that are linked together by biotic relationships. Asian forests in particular have lost many apex predators due to habitat loss. We studied a small forest patch in northeastern Bangladesh, Satchari National Park, to determine density and diversity of nocturnal mammals and evaluate their relationships. Transects were walked from February 2015 to July 2016 and density was estimated using distance sampling. Nine species of mammals (5 arboreal and 4 ground-dwelling) were encountered. Densities of the common palm civets, Paradoxurus hermaphrodites, Bengal slow loris, Nycticebus bengalensis, were the highest (19.48 and 15.03 individuals/km2). Density of small Indian civets, large Indian civets and Indian mongoose were lower (2.31-5.55 individuals/km2). Unexpectedly, a wide range of nocturnal mammals co-existed in this forest patch, in spite of fragmentation and severe disturbance. We did not find any significant association between any of the species studied, although this could be an artifact of low sample size. Conservation in Bangladesh remains a challenge due to high human population density. Thus, strict conservation measures are needed to permit the long-term survival of these species.

Application of decision analysis to evaluate recovery actions for threatened Snake River spring and summer chinook salmon (Oncorhynchus tshawytscha)

2001 ◽  
Vol 58 (12) ◽  
pp. 2431-2446 ◽  
Author(s):  
Calvin N Peters ◽  
David R Marmorek
Keyword(s):  
Decision Analysis ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Life Stage ◽  
Anthropogenic Factors ◽  
Snake River ◽  
Risk Averse ◽  
Term Survival ◽  
Wide Range

There is uncertainty about the importance of various factors in explaining declines of chinook salmon (Oncorhynchus tshawytscha) populations in the Snake River basin of Oregon and Idaho. This uncertainty has prevented implementation of long-term recovery actions for these stocks. We used simulation models and decision analysis to evaluate three management actions for seven index stocks of Snake River spring and summer chinook salmon: (i) continue current operation of the Columbia River hydropower system, (ii) maximize transportation of smolts, and (iii) natural river drawdown (breaching) of four Snake River dams. Decision analysis provided a useful approach for including multiple hypotheses about population responses to environmental and anthropogenic factors, systematically assessing the importance of alternative hypotheses, and identifying risk-averse recovery strategies that meet survival and recovery goals over a wide range of uncertainties. We found that the most influential uncertainties were related to hypothesized causes of estuary and ocean mortality. Current monitoring provides limited information on survival in this life stage; carefully designed management experiments are more likely to generate useful information. Given that these uncertainties exist, drawdown was the most risk-averse action, meeting long-term survival and recovery goals over a wider range of assumptions than the other actions.

scholarly journals Condition-dependent sex: who does it, when and why?

2016 ◽  
Vol 371 (1706) ◽  
pp. 20150539 ◽  
Author(s):  
Yoav Ram ◽  
Lilach Hadany
Keyword(s):  
Theoretical Prediction ◽  
Sexual Reproduction ◽  
Term Survival ◽  
Long Term Survival ◽  
Poor Condition ◽  
Empirical Results ◽  
Wide Range ◽  
Negative Condition

We review the phenomenon of condition-dependent sex—where individuals' condition affects the likelihood that they will reproduce sexually rather than asexually. In recent years, condition-dependent sex has been studied both theoretically and empirically. Empirical results in microbes, fungi and plants support the theoretical prediction that negative condition-dependent sex, in which individuals in poor condition are more likely to reproduce sexually, can be evolutionarily advantageous under a wide range of settings. Here, we review the evidence for condition-dependent sex and its potential implications for the long-term survival and adaptability of populations. We conclude by asking why condition-dependent sex is not more commonly observed, and by considering generalizations of condition-dependent sex that might apply even for obligate sexuals. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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