Antibacterial Immune Competence of Honey Bees (Apis mellifera) Is Adapted to
Different Life Stages and Environmental Risks



Abstract

The development of all honey bee castes proceeds through three different
life stages all of which encounter microbial infections to a various extent.
We have examined the immune strength of honey bees across all developmental
stages with emphasis on the temporal expression of cellular and humoral
immune responses upon artificial challenge with viable Escherichia coli
bacteria. We employed a broad array of methods to investigate defence
strategies of infected individuals: (a) fate of bacteria in the haemocoel;
(b) nodule formation and (c) induction of antimicrobial peptides (AMPs).
Newly emerged adult worker bees and drones were able to activate efficiently
all examined immune reactions. The number of viable bacteria circulating in
the haemocoel of infected bees declined rapidly by more than two orders of
magnitude within the first 4–6 h post-injection (p.i.), coinciding with the
occurrence of melanised nodules. Antimicrobial activity, on the other hand,
became detectable only after the initial bacterial clearance. These two
temporal patterns of defence reactions very likely represent the
constitutive cellular and the induced humoral immune response. A unique
feature of honey bees is that a fraction of worker bees survives the winter
season in a cluster mostly engaged in thermoregulation. We show here that
the overall immune strength of winter bees matches that of young summer bees
although nodulation reactions are not initiated at all. As expected, high
doses of injected viable E.coli bacteria caused no mortality in larvae or
adults of each age. However, drone and worker pupae succumbed to challenge
with E.coli even at low doses, accompanied by a premature darkening of the
pupal body. In contrast to larvae and adults, we observed no fast clearance
of viable bacteria and no induction of AMPs but a rapid proliferation of
E.coli bacteria in the haemocoel of bee pupae ultimately leading to their
death.


Citation: Gätschenberger H, Azzami K, Tautz J, Beier H (2013) Antibacterial
Immune Competence of Honey Bees (Apis mellifera) Is Adapted to Different
Life Stages and Environmental Risks. PLoS ONE 8(6): e66415.
doi:10.1371/journal.pone.0066415

Editor: Muriel Moser, Université Libre de Bruxelles, Belgium


Received: February 13, 2013; Accepted: May 3, 2013; Published: June 17, 2013

More here:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066415


Kind regards,

Ghislain De Roeck,
Belgium.

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