Muscles provide protection during microbial infection by activating innate immune response pathways in Drosophila and zebrafish

Abstract

Muscle contraction brings about movement and locomotion in animals. However, muscles have also been implicated in several atypical physiological processes including immune response. The role of muscles in immunity and the mechanism involved has not been deciphered yet. In this paper, using Drosophila indirect flight muscles (IFMs) as a model, we show that muscles are immune responsive tissues. Flies with defective IFMs are incapable of mounting a potent humoral immune response. The IFMs produce anti-microbial peptides (AMPs) upon immune challenge through the activation of canonical signaling pathways. IFM-synthesized AMPs are essential for survival upon infection. The trunk muscles of zebrafish, a vertebrate model system, also possess the capacity to mount an immune response against bacterial infections, thus establishing that immune responsiveness of muscles is evolutionarily conserved. Our results suggest that physiologically fit muscles may boost the innate immune response of an individual.