Tolerance and Immunity: Opposite Outcomes of Microbial Antigen Stimulation

The immune system is remarkable in many ways. It exerts immunity to defend us from foreign pathogens, while it is also responsible for maintaining tolerance to avoid autoimmune diseases and allergy. This thesis includes three separate papers concerning both tolerance and immunity. In paper I we report that repeated antigen stimulation results in an increased proportion of Foxp3+ cells in the CD4+ population of T cells in mice. This was caused by a decreased number of antigen-reactive conventional CD4+ T cells rather than by de novo development of Foxp3+ Tregs. Proliferation of naive transferred CD4+ T cells was inhibited in repeatedly immunized mice and cells transferred from such mice into naive recipients were shown to be anergic. Finally, we demonstrate that the in vitro anergy is partially dependent on Foxp3+ cells whereas the in vivo anergy is not. In paper II, bone marrow-derived dendritic cells from IFN-β-/- mice were used to study the role of IFN-β in TLR2-mediated induction of iNOS. We demonstrate that the TLR2 ligands LTA and Pam3Cys induce the expression of iNOS in an IFN-β dependent manner. Furthermore, iNOS activity induced by these ligands did not require receptor internalization or endosomal maturation, and was differentially dependent on the TRIF- and IRF3 molecules. In paper III we have investigated the impact of in vivo 5757-treatment on cells in lymph nodes and spleen of steady state mice. We show that the cell number of a specific DC-subset, CD4+CD8α-, is selectively reduced in the spleen of 5757-treated mice. The reduction was reversible and was not caused by decreased cell division or increased apoptosis. Finally, the overall structure of the marginal zone, where CD4+CD8α- DCs normally reside, remained intact in mice treated with 5757, ruling out the hypothesis that these DCs would emigrate from the spleen because of a disrupted marginal zone

Contemporary Parallel Diversification, Antipredator Adaptations and Phenotypic Integration in an Aquatic Isopod

It is increasingly being recognized that predation can be a strong diversifying agent promoting ecological divergence. Adaptations against different predatory regimes can emerge over short periods of time and include many different traits. We studied antipredator adaptations in two ecotypes of an isopod (Asellus aquaticus) that have, diverged in parallel in two Swedish lakes over the last two decades. We quantified differences in escape speed, morphology and behavior for isopods from different ecotypes present in these lakes. Isopods from the source habitat (reed) coexist with mainly invertebrate predators. They are more stream-profiled and have higher escape speeds than isopods in the newly colonized stonewort habitat, which has higher density of fish predators. Stonewort isopods also show more cautious behaviors and had higher levels of phenotypic integration between coloration and morphological traits than the reed isopods. Colonization of a novel habitat with a different predation regime has thus strengthened the correlations between pigmentation and morphology and weakened escape performance. The strong signature of parallelism for these phenotypic traits indicates that divergence is likely to be adaptive and is likely to have been driven by differences in predatory regimes. Furthermore, our results indicate that physical performance, behavior and morphology can change rapidly and in concert as new habitats are colonized

Resolution of conflict between parental genomes in a hybrid species

AbstractThe development of reproductive barriers against parent species is crucial during hybrid speciation, and post-zygotic isolation can be important in this process. Genetic incompatibilities that normally isolate the parent species can become sorted in hybrids to form reproductive barriers towards either parent. However, the extent to which this sorting process is systematically biased and therefore predictable in which loci are involved and which alleles are favored is largely unknown. Theoretically, reduced fitness in hybrids due to the mixing of differentiated genomes can be resolved through rapid evolution towards allelic combinations ancestral to lineage-splitting of the parent species, as these alleles have successfully coexisted in the past. However, for each locus, this effect may be influenced by its chromosomal location, function, and interactions with other loci. We use the Italian sparrow, a homoploid hybrid species that has developed post-zygotic barriers against its parent species, to investigate this prediction. We show significant bias towards fixation of the ancestral allele among 57 nuclear intragenic SNPs, particularly those with a mitochondrial function whose ancestral allele came from the same parent species as the mitochondria. Consistent with increased pleiotropy leading to stronger fitness effects, genes with more protein-protein interactions were more biased in favor of the ancestral allele. Furthermore, the number of protein-protein interactions was especially low among candidate incompatibilities still segregating within Italian sparrows, suggesting that low pleiotropy allows steep intraspecific clines in allele frequencies to form. Finally, we report evidence for pervasive epistatic interactions within one Italian sparrow population, particularly involving loci isolating the two parent species but not hybrid and parent. However there was a lack of classic incompatibilities and no admixture linkage disequilibrium. This suggests that parental genome admixture can continue to constrain evolution and prevent genome stabilization long after incompatibilities have been purged.</jats:p

Phenotypic Plasticity in Response to the Social Environment: Effects of Density and Sex Ratio on Mating Behaviour Following Ecotype Divergence

The ability to express phenotypically plastic responses to environmental cues might be adaptive in changing environments. We studied phenotypic plasticity in mating behaviour as a response to population density and adult sex ratio in a freshwater isopod (Asellus aquaticus). A. aquaticus has recently diverged into two distinct ecotypes, inhabiting different lake habitats (reed Phragmites australis and stonewort Chara tomentosa, respectively). In field surveys, we found that these habitats differ markedly in isopod population densities and adult sex ratios. These spatially and temporally demographic differences are likely to affect mating behaviour. We performed behavioural experiments using animals from both the ancestral ecotype (“reed” isopods) and from the novel ecotype (“stonewort” isopods) population. We found that neither ecotype adjusted their behaviour in response to population density. However, the reed ecotype had a higher intrinsic mating propensity across densities. In contrast to the effects of density, we found ecotype differences in plasticity in response to sex ratio. The stonewort ecotype show pronounced phenotypic plasticity in mating propensity to adult sex ratio, whereas the reed ecotype showed a more canalised behaviour with respect to this demographic factor. We suggest that the lower overall mating propensity and the phenotypic plasticity in response to sex ratio have evolved in the novel stonewort ecotype following invasion of the novel habitat. Plasticity in mating behaviour may in turn have effects on the direction and intensity of sexual selection in the stonewort habitat, which may fuel further ecotype divergence

Effects of interspecific gene flow on the phenotypic variance–covariance matrix in Lake Victoria Cichlids

Quantitative genetics theory predicts adaptive evolution to be constrained along evolutionary lines of least resistance. In theory, hybridization and subsequent interspecific gene flow may, however, rapidly change the evolutionary constraints of a population and eventually change its evolutionary potential, but empirical evidence is still scarce. Using closely related species pairs of Lake Victoria cichlids sampled from four different islands with different levels of interspecific gene flow, we tested for potential effects of introgressive hybridization on phenotypic evolution in wild populations. We found that these effects differed among our study species. Constraints measured as the eccentricity of phenotypic variance–covariance matrices declined significantly with increasing gene flow in the less abundant species for matrices that have a diverged line of least resistance. In contrast, we find no such decline for the more abundant species. Overall our results suggest that hybridization can change the underlying phenotypic variance–covariance matrix, potentially increasing the adaptive potential of such populations

Introduction: Interrogating the 'everyday' politics of emotions in international relations

The focus on the everyday in this Special Issue reveals different kinds of emotional practices, their political effects and their political contestation within both micro- and macro-politics in international relations. The articles in this Special Issue address the everyday negotiation of emotions, shifting between the reproduction of hegemonic structures of feelings and emancipation from them. In other words, the everyday politics of emotions allows an exploration of who gets to express emotions, what emotions are perceived as (il)legitimate or (un)desirable, how emotions are circulated and under what circumstances. Consequently, we identify two thematic strands which emerge as central to an interrogation of ‘everyday’ emotions in international relations and which run through each of the contributions: first, an exploration of the relationship between individual and collective emotions and, second, a focus on the role of embodiment within emotions research and its relationship with the dynamics and structures of power

Genetic admixture despite ecological segregation in a North African sparrow hybrid zone (Aves, Passeriformes, Passer domesticus × Passer hispaniolensis)

Under different environmental conditions, hybridization between the same species might result in different patterns of genetic admixture. Particularly, species pairs with large distribution ranges and long evolutionary history may have experienced several independent hybridization events over time in different zones of overlap. In birds, the diverse hybrid populations of the house sparrow (Passer domesticus) and the Spanish sparrow (Passer hispaniolensis) provide a striking example. Throughout their range of sympatry, these two species do not regularly interbreed; however, a stabilized hybrid form (Passer italiae) exists on the Italian Peninsula and on several Mediterranean is‐ lands. The spatial distribution pattern on the Eurasian continent strongly contrasts the situation in North Africa, where house sparrows and Spanish sparrows occur in close vicinity of phenotypically intermediate populations across a broad mosaic hy‐ brid zone. In this study, we investigate patterns of divergence and admixture among the two parental species, stabilized and nonstabilized hybrid populations in Italy and Algeria based on a mitochondrial marker, a sex chromosomal marker, and 12 micros‐ atellite loci. In Algeria, despite strong spatial and temporal separation of urban early‐ breeding house sparrows and hybrids and rural late‐breeding Spanish sparrows, we found strong genetic admixture of mitochondrial and nuclear markers across all study populations and phenotypes. That pattern of admixture in the North African hybrid zone is strikingly different from i) the Iberian area of sympatry where we observed only weak asymmetrical introgression of Spanish sparrow nuclear alleles into local house sparrow populations and ii) the very homogenous Italian sparrow population where the mitogenome of one parent (P. domesticus) and the Z‐chromosomal marker of the other parent (P. hispaniolensis) are fixed. The North African sparrow hybrids provide a further example of enhanced hybridization along with recent urbanization and anthropogenic land‐use changes in a mosaic landscape.Fil: Päckert, Martin. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Ait Belkacem, Abdelkrim. Université de Djelfa; ArgeliaFil: Wolfgramm, Hannes. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Gast, Oliver. Institute of Vertebrate Biology Brno y Masaryk University ; República ChecaFil: Canal Piña, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Giacalone, Gabriele. Cooperativa Silene; ItaliaFil: Lo Valvo, Mario. Universita Degli Studi Di Palermo.; ItaliaFil: Vamberger, Melita. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Wink, Michael. Ruprecht Karls Universitat Heidelberg.; AlemaniaFil: Martens, Jochen. Johannes Gutenberg Universitat Mainz; AlemaniaFil: Stuckas, Heiko. Leibniz Institution for Biodiversity and Earth System Research, Dresden; Alemani