Social Immunity Research Articles

Individual and social immune mechanisms of the honey bee (Apis mellifera)

Honey bees (Apis mellifera) are constantly exposed to contact with many types of pathogens. However, during evolution they developed a number of immune mechanisms. At the individual level, they comprise 1) resistance mechanisms associated with anatomical and physiological barriers of the body, 2) cell-mediated immunity involving hemocytes (including plasmocytes, lamellocytes, and granulocytes), 3a) congenital humoral resistance related to the activity of lysozyme (N-acetylmuramylhydrolase), the prophenylooxidase system (ProPO) and hemagglutinins (lectins), and 3b) induced humoral resistence based on the action of antimicrobial peptides: apidicines, hymenoptecin, and defensins. In addition to the individual resistance of each bee, there is also a defense mechanism activated at the colony level. Shared secretion resistance is connected with the presence of antipathogenic compounds in secreta and in bee products. Social immunity is associated with hygienic and nursing behaviors, as well as with age polyethism in the colony, swarming (and the emergence of rebel workers), and the changing behavior of sick individuals. Many aspects and interactions between different types of resistance and immunity still remain unexplored. However, current research trends revolve around clarifying uncertainties so as to strengthen the natural resistance of bees and fight against pathogens that threaten the insects..

Systematic and communicative theory of the protest movement: protest as “an alternative without an alternative”

The author argues that the causes of the protest movements are not very clear. So, as it is denoted in the article, one could apply to the systematic and theoretical approach for the interpretation of empirical phenomenology and taxonomy of protest.The author argues that such «traditional» approaches for the interpretation of the protest movement as the structural-critical and resource-mobilization approaches are insolvent, so one should applies to the systematic and communicative approach for the analysis of the various forms of social radicalism as a special type of communication.The author suggests to interpret protest movements as a specific communication, that is oriented towards a common binary media code for common communications and towards a common protest theme. Applying to the systematic and communicative approach of the protest movement’ analysis, the author introduces the category of social immunity as a category of description and explanation of the deviant forms of communication.

Impact of colony size on survival and sanitary strategies in fungus-infected ant colonies

Group-living species have to deal with higher risks of exposure to pathogens and of disease propagation between group members. Insect societies have therefore evolved behaviours that contribute to the social immunity of the whole colony. Here, we investigate how the sanitary strategies displayed by ants depend on colony size, which is known to influence their social organisation. Myrmica rubra ant colonies of different sizes were faced with waste items that were infected or not by the entomopathogen fungus Metarhizium brunneum. By keeping nest parameters and pathogen loads proportional to colony size, we show that the largest colonies less suffered from exposure to life-threatening spores. Indeed, the largest colonies showed the lowest mortality rates and were the fastest to reject all the infected waste items out from their nest. Unexpectedly, small-sized colonies displayed distinct sanitary strategies according to the pathogenicity of the waste items. When challenged with fungus-bearing items, they opted out for an “emergency strategy” in which workers first moved out from their nest carrying brood and reintegrate it after sanitization by waste-transporting individuals. This demonstrates the behavioural plasticity of ant colonies of which both the size and the sanitary threat determine the efficiency and the type of hygienic responses to hygienic challenges. Insect societies have evolved several collective hygienic behaviours that contribute to their “social immunity”. Here, we found out that both internal and external factors determine the efficiency and the type of hygienic responses to waste items introduced in an ant colony. In particular, small-sized colonies demonstrated a behavioural plasticity with distinct sanitary strategies according to the pathogenicity of the waste items. Such a plasticity appears to be an adaptive way to limit exposure of larvae to pathogens and hence to preserve colony development. It also raises some questions about the origin of the differences in worker’s internal threshold allowing colonies to shift between sanitary strategies.

Social response of healthy honeybees towards Nosema ceranae-infected workers: care or kill?

Honeybees are living densely packed in colonies which extremely facilitates intracolonial pathogen transmission from one individual to another. In addition to the defence by the innate immune system, various behavioural adaptations allow honeybees to avoid or reduce pathogen transmission, also coined ‘social immunity’. Here, we show that infections with the intestinal parasite Nosema ceranae lead to altered behaviour going beyond a ‘care-kill dichotomy’ within the society. We show that the response of healthy workers can be highly variable ranging from avoidance to enhanced social interactions that even lead to killing of infected nestmates in some cases. These behavioural defence mechanisms may help in reducing the spread of the disease in the colony. Thus, honeybees can respond highly variable and not just with one behavioural response after recognising an infected worker even when fighting against the same parasite species.

No evidence for social immunity in co-founding queen associations

Ant queens often associate to found new colonies, yet the benefits of this behaviour remain unclear. A major hypothesis is that queens founding in groups are protected by social immunity and can better resist disease than solitary queens, due to mutual grooming, sharing of antimicrobials, or higher genetic diversity among their workers. We tested this hypothesis by manipulating the number of queens in incipient colonies of Lasius niger and measuring their resistance to the fungal entomopathogen Metarhizium brunneum. We found no evidence for social immunity in associations of founding queens. First, co-founding queens engaged in self-grooming, but performed very little allo-grooming or trophallaxis. Second, co-founding queens did not exhibit higher pathogen resistance than solitary queens, and their respective workers did not differ in disease resistance. Finally, queens founding in groups increased their investment in a component of individual immunity, as expected if they do not benefit from social immunity but respond to a higher risk of disease. Overall, our results provide no evidence that joint colony founding by L. niger queens increases their ability to resist fungal pathogens.

Resin foraging dynamics in Varroa destructor‐infested hives: a case of medication of kin?

Social insects have evolved colony behavioral, physiological, and organizational adaptations (social immunity) to reduce the risks of parasitization and/or disease transmission. The collection of resin from various plants and its use in the hive as propolis is a clear example of behavioral defense. For Apis mellifera, an increased propolis content in the hive may correspond to variations in the microbial load of the colony and to a downregulation of an individual bee's immune response. However, many aspects of such antimicrobial mechanism still need to be clarified. Assuming that bacterial and fungal infection mechanisms differ from the action of a parasite, we studied the resin collection dynamics in Varroa destructor-infested honeybee colonies. Comparative experiments involving hives with different mite infestation levels were conducted in order to assess the amount of resin collected and propolis quality within the hive, over a 2-year period (2014 and 2015). Our study demonstrates that when A. mellifera colonies are under stress because of Varroa infestation, an increase in the number of resin foragers is recorded, even if a general intensification of the foraging activity is not observed. A reduction in the total polyphenolic content in propolis produced in infested versus uninfested hives was also noticed. Considering that different propolis types show varying levels of inhibition against a variety of honey bee pathogens in vitro, it would be very important to study the effects against Varroa of two diverse types of propolis: from Varroa-free and from Varroa-infested hives.

Social Immunity: Emergence and Evolution of Colony-Level Disease Protection.

Social insect colonies have evolved many collectively performed adaptations that reduce the impact of infectious disease and that are expected to maximize their fitness. This colony-level protection is termed social immunity, and it enhances the health and survival of the colony. In this review, we address how social immunity emerges from its mechanistic components to produce colony-level disease avoidance, resistance, and tolerance. To understand the evolutionary causes and consequences of social immunity, we highlight the need for studies that evaluate the effects of social immunity on colony fitness. We discuss the roles that host life history and ecology have on predicted eco-evolutionary dynamics, which differ among the social insect lineages. Throughout the review, we highlight current gaps in our knowledge and promising avenues for future research, which we hope will bring us closer to an integrated understanding of socio-eco-evo-immunology.

Propolis envelope in Apis mellifera colonies supports honey bees against the pathogen, Paenibacillus larvae

Honey bees have immune defenses both as individuals and as a colony (e.g., individual and social immunity). One form of honey bee social immunity is the collection of antimicrobial plant resins and the deposition of the resins as a propolis envelope within the nest. In this study, we tested the effects of the propolis envelope as a natural defense against Paenibacillus larvae, the causative agent of American foulbrood (AFB) disease. Using colonies with and without a propolis envelope, we quantified: 1) the antimicrobial activity of larval food fed to 1–2 day old larvae; and 2) clinical signs of AFB. Our results show that the antimicrobial activity of larval food was significantly higher when challenged colonies had a propolis envelope compared to colonies without the envelope. In addition, colonies with a propolis envelope had significantly reduced levels of AFB clinical signs two months following challenge. Our results indicate that the propolis envelope serves as an antimicrobial layer around the colony that helps protect the brood from bacterial pathogen infection, resulting in a lower colony-level infection load.

A theoretical exploration of dietary collective medication in social insects

Animals often alter their food choices following a pathogen infection in order to increase immune function and combat the infection. Whether social animals that collect food for their brood or nestmates adjust their nutrient intake to the infection states of their social partners is virtually unexplored. Here we develop an individual-based model of nutritional geometry to examine the impact of collective nutrient balancing on pathogen spread in a social insect colony. The model simulates a hypothetical social insect colony infected by a horizontally transmitted parasite. Simulation experiments suggest that collective nutrition, by which foragers adjust their nutrient intake to simultaneously address their own nutritional needs as well as those of their infected nestmates, is an efficient social immunity mechanism to limit contamination when immune responses are short. Impaired foraging in infected workers can favour colony resilience when pathogen transmission rate is low (by reducing contacts with the few infected foragers) or trigger colony collapse when transmission rate is fast (by depleting the entire pool of foragers). Our theoretical examination of dietary collective medication in social insects suggests a new possible mechanism by which colonies can defend themselves against pathogens and provides a conceptual framework for experimental investigations of the nutritional immunology of social animals.

知覚されたソーシャルサポートと免疫系の関連 : ヘルスプロモーションからみたソーシャルサポート研究の可能性(シンポジウム : ヘルスプロモーションの心身医学)(2003年/第44回日本心身医学会総会/沖縄)

知覚されたソーシャルサポートと免疫系の関連 : ヘルスプロモーションからみたソーシャルサポート研究の可能性(シンポジウム : ヘルスプロモーションの心身医学)(2003年/第44回日本心身医学会総会/沖縄)

Chronic exposure to neonicotinoids reduces honey bee health near corn crops.

Experiments linking neonicotinoids and declining bee health have been criticized for not simulating realistic exposure. Here we quantified the duration and magnitude of neonicotinoid exposure in Canada's corn-growing regions and used these data to design realistic experiments to investigate the effect of such insecticides on honey bees. Colonies near corn were naturally exposed to neonicotinoids for up to 4 months-the majority of the honey bee's active season. Realistic experiments showed that neonicotinoids increased worker mortality and were associated with declines in social immunity and increased queenlessness over time. We also discovered that the acute toxicity of neonicotinoids to honey bees doubles in the presence of a commonly encountered fungicide. Our work demonstrates that field-realistic exposure to neonicotinoids can reduce honey bee health in corn-growing regions.

Loss of attraction for social cues leads to fungal-infected Myrmica rubra ants withdrawing from the nest

In social insects, individuals infected by pathogens withdraw from the nest, preventing the spread of diseases among genetically related nestmates and thereby contributing to the ‘social immunity’ of the colony. Here we investigated the extent to which the isolation of sick ants correlates with changes in their behavioural responses to environmental stimuli that serve as nest-related cues, including light, colony odour and physical presence of nestmates. Myrmica rubra ant workers infected by Metarhizium brunneum fungus showed a weak but constant attraction to light. By contrast, the progressive withdrawal of moribund workers from the nest appeared to be concomitant with a decline in their attraction towards nestmates or colony odour, which started on the third day after infection. We hypothesized that the fungus impaired the olfactory system of infected ants, preventing them from adequately reacting to chemical blends involved in colony marking and nestmate recognition. Instead of being an active behaviour, the social seclusion of sick ants appears to be the simple outcome of their increasing difficulty in orienting themselves towards nest-related cues. This phenomenon was reinforced by minor positive phototropism and the progressive dysfunction of motor skills as the infection progressed.

Expression monitoring of relevant sensitivity genes in honey bee antennae and their relationship with Hygienic Behavior

Honeybees are very important microlivestock, not only for the economic value of their productions but also for the crucial role they fulfill as pollinators. Recently, colony losses have been recorded throughout Europe and the reasons underpinning such phenomenon can be addressed to agro-chemicals and pathogens. Among the latter, the parasitic mite Varroa destructor is considered the principal mortality cause. Hygienic behavior (HB) in honeybee ( Apis mellifera ) involves the detection and removal of brood affected by bacterial, fungal diseases, and parasitization. This behavior is part of a series of strategies evolved by social insects known as social immunity, which confers disease resistance thanks to the persistent elimination of pathogens and parasites from the hive, limiting their multiplication and the infection of other bees. It has previously reported that physiological changes in peripheral sense tissues of insects influence the behavioral state of individuals, and it has been suggested that changes in gene expression at antennal level can contribute to shifts in the behavioral states of honeybees. Moreover, it has previously reported that antennae hold a key role in the process of recognition of abnormalities in the brood by honeybees. The aim of the work was to investigate the expression level of selected genes (Obp3, Obp4, Obp16, Obp18, Act5C, Mblk-1) through RealTime-PCR in honeybee antennae. These targets are reported as potential biomarkers of HB in previous transcriptomic and proteomic studies. Hygienic behavior has been measured in the field through optimized freeze-killed-brood method on 10 colonies, from which workers of known age (15 days old) have been collected for molecular analysis. Preliminary results show that Obp3 is the least expressed among the tested genes, but its expression pattern is linked to the HB value; in particular, highly hygienic colonies express Obp3 significantly at higher rate with respect to the lower HB group of colonies.

Obp4 and Act5C gene expression is related to Hygienic behavior in honeybee families

Honeybees (Apis mellifera) evolved social immunity mechanisms based on coordinated behavioral mechanisms for reducing the spread of pathogens and parasites. In particular, Hygienic Behavior (HB) is an actively participation of family defense by uncapping and removal of dead, diseased or parasitized brood. Currently, HB evaluation is performed only by in-field empirical assays, and suitable molecular markers that could allow the discrimination between families with High and Non-High HB score are not yet available. The research activity was characterized by a transversal approach: from in-field phenotypic characterization, to expression profiling of selected coding genes in honeybee brains. The expression analysis was performed on pools of 15 days-old honeybees collected in spring 2017 from 10 different colonies (5 with high HB and 5 with low HB scores). The brains were dissected and total RNA was purified. After quantitation and quality evaluation, the extracted RNAs were reverse transcribed to cDNAs and Real Time PCR was performed on different target genes (Act5C, Mblk-1, Obp3, Obp4, Obp16 and Obp18) previously showed by transcriptomic and proteomic studies to be involved in HB. The comparative analysis of RT-PCR threshold cycles (Ct) showed that Mblk-1 was the least expressed gene among the analyzed targets. Most importantly, statistical analysis of expression data validated (p<0.05) the delta-Ct between Obp4 and Act5C as a predictive index of high vs low HB score. These results confirmed the findings obtained through a preliminary experiment performed in spring 2016.

Pareto optimality and strategy-proofness in group argument evaluation

An inconsistent knowledge base can be abstracted as a set of arguments and a defeat relation among them. There can be more than one consistent way to evaluate such an argumentation graph. Collective argument evaluation is the problem of aggregating the opinions of multiple agents on how a given set of arguments should be evaluated. It is crucial not only to ensure that the outcome is logically consistent, but also satisfies measures of social optimality and immunity to strategic manipulation. This is because agents have their individual preferences about what the outcome ought to be. In the current paper, we analyze three previously introduced argument-based aggregation operators with respect to Pareto optimality and strategy proofness under different general classes of agent preferences. We highlight fundamental trade-offs between strategic manipulability and social optimality on one hand, and classical logical criteria on the other. Our results motivate further investigation into the relationship between social choice and argumentation theory. The results are also relevant for choosing an appropriate aggregation operator given the criteria that are considered more important, as well as the nature of agents' preferences.

Inducible versus constitutive social immunity: examining effects of colony infection on glucose oxidase and defensin-1 production in honeybees.

Honeybees use a variety of defence mechanisms to reduce disease infection and spread throughout the colony. Many of these defences rely on the collective action of multiple individuals to prevent, reduce or eradicate pathogens—often referred to as ‘social immunity’. Glucose oxidase (GOX) and some antimicrobial peptides (e.g. defensin-1 or Def1) are secreted by the hypopharyngeal gland of adult bees on larval food for their antiseptic properties. Because workers secrete these compounds to protect larvae, they have been used as ‘biomarkers’ for social immunity. The aim of this study was to investigate if GOX and Def1 are induced after pathogen exposure to determine whether its production by workers is the result of a collective effort to protect the brood and colony in response to a pathogen challenge. Specifically, we quantified GOX and Def1 in honeybee adults before and after colony-level bacterial infection by American foulbrood ((AFB), Paenibacillus larvae). Overall, our results indicate that levels of GOX and Def1 are not induced in response to pathogenic infections. We therefore conclude that GOX and Def1 are highly constitutive and co-opted as mechanisms of social immunity, and these factors should be considered when investigating immunity at the individual and colony level in social insects.

Propolis Counteracts Some Threats to Honey Bee Health.

Honey bees (Apis mellifera) are constantly dealing with threats from pathogens, pests, pesticides and poor nutrition. It is critically important to understand how honey bees’ natural immune responses (individual immunity) and collective behavioral defenses (social immunity) can improve bee health and productivity. One form of social immunity in honey bee colonies is the collection of antimicrobial plant resins and their use in the nest architecture as propolis. We review research on the constitutive benefits of propolis on the honey bee immune system, and its known therapeutic, colony-level effects against the pathogens Paenibacillus larvae and Ascosphaera apis. We also review the limited research on the effects of propolis against other pathogens, parasites and pests (Nosema, viruses, Varroa destructor, and hive beetles) and how propolis may enhance bee products such as royal jelly and honey. Although propolis may be a source of pesticide contamination, it also has the potential to be a detoxifying agent or primer of detoxification pathways, as well as increasing bee longevity via antioxidant-related pathways. Throughout this paper, we discuss opportunities for future research goals and present ways in which the beekeeping community can promote propolis use in standard colonies, as one way to improve and maintain colony health and resiliency.

Odorant cues linked to social immunity induce lateralized antenna stimulation in honey bees (Apis mellifera L.)

Hygienic behaviour (HB) is a social immunity trait in honey bees (Apis mellifera L.) whereby workers detect, uncap and remove unhealthy brood, improving disease resistance in the colony. This is clearly economically valuable; however, the molecular mechanism behind it is not well understood. The freeze-killed brood (FKB) assay is the conventional method of HB selection, so we compared odour profiles of FKB and live brood to find candidate HB-inducing odours. Surprisingly, we found that significantly more brood pheromone (β-ocimene) was released from FKB. β-ocimene abundance also positively correlated with HB, suggesting there could be a brood effect contributing to overall hygiene. Furthermore, we found that β-ocimene stimulated worker antennae in a dose-dependent manner, with the left antennae responding significantly stronger than right antennae in hygienic bees, but not in non-hygienic bees. Five other unidentifiable compounds were differentially emitted from FKB which could also be important for HB. We also compared odour profiles of Varroa-infested brood to healthy brood and found an overall interactive effect between developmental stage and infestation, but specific odours did not drive these differences. Overall, the data we present here is an important foundation on which to build our understanding the molecular mechanism behind this complex behaviour.

Cuticular hydrocarbon cues of immune-challenged workers elicit immune activation in honeybee queens.

Recently, evidence has shown that variations in the cuticular hydrocarbons (CHCs) profile allow healthy honeybees to identify diseased nestmates, eliciting agonistic responses in the former. Here, we determined whether these 'immunologic cues' emitted by diseased nestmates were only detected by workers, who consequently took hygienic measures and excluded these individuals from the colony, or whether queens were also able to detect these cues and respond accordingly. Healthy honeybee queens were exposed to (i) healthy, (ii) Ringer-injected and (iii) lipopolysaccharide (LPS)-injected nestmates by allowing direct body contact. Quantitative differences in the CHC profiles of these three groups were measured using GC-MS. The transcript levels of the products of four genes that encode for antimicrobial peptides (AMPs), which are part of the queen's immune response, were measured in bees exposed to direct contact using qPCR. A significant increase in the transcript levels of these AMP genes over baseline levels in queens was observed when body contact was allowed between the queens and the Ringer- and LPS-injected nestmates. These results provide the first evidence that the detection of CHCs contributes to the initiation of an immune response in insects. In an additional experiment, CHCs were extracted from diseased workers and directly presented to queens, which also evoked a similar immune response. A potential mechanism that relied on volatile compounds could be ruled out by conducting a distance experiment. The study helps to expand our knowledge of chemical communication in insects and sheds light on a likely new mechanism of social immunity.

Neutrality in foreign aid

Since the late 1990s, researchers have been predicting that the era of neutrality in aid politics is coming to an end and that foreign organizations will have to take a more engaged stance. Yet while the boundaries between humanitarianism and development are fading, in some cases the neutrality norm is actually expanding rather than giving way to an engaged paradigm. Recognizing that the principles of neutrality and independence have different meanings for different actors and that they are applied in various ways, this article examines how the humanitarian developers—small NGOs operating in Jonglei State in South Sudan—use these paradigms. The article shows that their specific variant of neutrality is not so much a pragmatic tool enabling operations in difficult settings, but instead is a structural form of identity. In this variation, neutrality is not about the absence of a political stance, but about standing apart from social structures and social immunity.