Research
Social immunity
In addition to the individual immunity of all colony members, social insects protect their colonies from disease by cooperative defences. This social immunity acts to prevent contamination of the colony, infection of colony members and disease transmission, hence to improve fitness of the colony.
The concept
Protection of the superorganism
Social insect colonies are „superorganisms”. Like cells in a body, the different insects specialize on different tasks: queens and males reproduce, whilst the workers are typically sterile and perform colony maintenance tasks. Social immunity describes how the colonies as reproductive entities are protected from disease.
Nest hygiene
Preventing colony contamination
Pathogens need to enter and establish in the colony to later cause infection of colony members. To prevent colony contamination, ants constantly and prophylactically disinfect their nest, particularly their brood pile, with antimicrobials like their formic-acid rich poison.
Sanitary care
Preventing current infection
Pathogen-exposed ants receive immediate sanitary care by their healthy colony members, effectively preventing infection of the contaminated individuals. Sanitary care combines mechanical removal of infectious particles by grooming and antimicrobial sanitation.
Social immunisation
Preventing future infections
Social contact with infectious colony members causes pathogen transmission to previously healthy colony members. Often, this cross-contamination only leads to low-level infection of the colony members. Instead of causing disease, this boosts the individual immune system of the colony members and induces a protective immunisation.
Treating infection
Preventing pathogen replication
Ants treat infections and thereby prevent pathogen replication and hence disease transmission through the colony. They are able to detect infections already during the non-infectious incubation period by chemical cues and to treat them by complex behaviors and use of antimicrobials. This fast detection of infections is driven by active disease signalling of the infected individuals themselves.
Organisational immunity
Preventing disease spread
Pathogens use the social interaction networks of their hosts for transmission to new host individuals. Social insect colonies react to pathogen entry into the colony by re-organisation of their social interaction networks. Contaminated ants, but also their peers, reduce contact to the remaining colony members. This leads to a highly efficient reduction of disease spread through the colony.
Key publications of our group
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(Trends Parasitol, 2024) Unconditional versus condition-dependent social immunity
In this review, we analyzed how unconditional social immunity in superorganism differs from condition-dependent social immunity in helper associations. Read more
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(Nat Comm, 2023) Dynamic pathogen detection and social feedback shape collective hygiene in ants
In this study, we demonstrated that noisy individual decisions, based on only local, incomplete, yet dynamically updated information about pathogen threats and social feedback, can result in powerful collective disease defenses. Read more
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(Nat Ecol Evol, 2023) Pathogen evasion of social immunity
In this study, we analysed the potential of fungal pathogens to adapt to individual vs social immunity of their social insect hosts. We found that lines adapted to groups of ants providing sanitary care were able to evade this collective defence by reducing their ergosterol levels, a key fungal component that triggers grooming. Read more
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(Curr Biol, 2019) Social immunity in insects
This primer summarises the concept of social immunity and highlights the difference between the complexity of cooperative disease defences between social insects that form a superorganism to other social groups that consist of totipotent group members. Read more
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(Science, 2018) Social network plasticity decreases disease transmission in a eusocial insect
The study shows how ant colonies can modulate their social interaction networks after pathogen exposure to contain the disease. We found social distancing performed by infectious foragers and documented how this limits pathogen transmission to the vulnerable queen and nurses in the center of the colony. Read more
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(PNAS, 2018) Ants avoid superinfections by performing risk-adjusted sanitary care
The study demonstrates how ants adjust their sanitary care behaviours based on previous encounters with pathogens. Read more
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(eLife, 2018) Destructive disinfection of infected brood prevents systemic disease spread in ant colonies
The study describes that workers perform destructive disinfection of fatally-infected brood, thereby preventing pathogen spread within the colony. Read more
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(Curr Biol, 2013) Ants disinfect fungus-exposed brood by oral uptake and spread of their poison
In this work, we showed that Formicine ants combine the mechanical removal of infectious pathogen stages from exposed colony members with chemical disinfection through the application of their poison, the main active component of which being formic acid. Read more
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(PLoS, 2012) Social transfer of pathogenic fungus promotes active immunisation in ant colonies
In this study, we identified the mechanism of social immunisation in ants: close social contact with pathogen-exposed individuals leads to a transfer of low levels of infectious pathogens to colony members. Instead of causing disease, this triggers a specific immune response, providing future protection against the pathogen. Read more
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(Philos Trans R Soc B, 2009) Analogies in the evolution of individual and social immunity
In this review, we introduced the idea that the cooperative anti-parasite defences of social insect colonies follow the same organisational principle – across biological levels – as the organismal immune system of multicellular organisms. Read more
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(Current Biology, 2007) Social Immunity
This review describes the collective and cooperative disease defenses expressed by social insects and how they provide ‘social immunity’ to the colony. Social insect colonies thus show multiple layers of immunity: their individual immune system, combined with cooperative sanitary care and infection management. Read more