Cold-induced immune activation in chill-susceptible insects

Chilling injuries in chill-susceptible insects, such as the model dipteran Drosophila melanogaster, have been well-documented as a consequence of stressful low-temperature exposures. Cold stress also causes upregulation of genes in the insect immune pathways, some of which are also upregulated following other forms of sterile stress. The adaptive significance and underlying mechanisms surrounding cold-induced immune activation, however, are still unclear. Here, we review recent work on the roles of reactive oxygen species, damage-associated molecular patterns, and antimicrobial peptides in insect immune signaling or function. Using this emerging knowledge, we propose a conceptual model linking biochemical and molecular causes of immune activation to its consequences during and following cold stress.