Depletion of phagocytic hemocytes with clodronate liposomes attenuates the innate immune system of western honey bee (Apis mellifera)

The western honey bee (Apis mellifera) is a eusocial insect that plays a significant role in ecosystem balance and pollination of plants and food crops. In Apis mellifera, the innate immune system is divided into two primary mechanisms of immune defense; soluble effector molecules (such as antimicrobial peptides) that mediate humoral responses, and cellular immune responses such as phagocytosis and encapsulation that promote pathogen killing. Immune cells commonly referred to as hemocytes, are a critical component of the immune system and produce immune factors which either facilitate or suppress pathogen development in bees. Despite their importance in pathogen development, understanding of their basic biology and molecular mechanisms is limited. In this study, a combination of pharmacological and molecular tools was utilized to investigate the functional role of bee hemocytes in pathogen infection. Clodronate liposome was used to deplete phagocytic hemocytes and elucidate their role in immune response and survival against Staphylococcus aureus, and Escherichia coli infection. Together, these results represent a significant advancement in our understanding of the basic biology of honey bee hemocytes and their role in the honey bee immune response.