Clodronate liposomes untangle the role of hemocytes in

Introduction: The cellular immune response, mediated by hemocytes, is a fundamental component of honey bee ( Methods: Five-day-old (nurses) and fifteen-day-old (foragers) honey bees were treated with CLD, control liposomes, PBS, or left untreated, then exposed at either 32°C or 22°C and challenged with the gram-negative bacterium, Results: The CLD application demonstrated significant reductions in granulocyte and prohemocyte populations, indicating the highest vulnerability. A temperature drop to 22°C buffered the negative impact on survival of CLD-induced immunosuppression. While bacterial challenges universally reduced hemocyte counts, we found an age-dependent difference where nurses maintained significantly higher baseline total hemocyte counts than foragers. Furthermore, temperature did not affect overall total hemocyte counts in 5-day-old nurse bees, but in 15-day-old foragers, it significantly modulated the hemocyte response to bacterial infection. Conclusion: Our findings show that hemocyte function is non-uniform, with specific subtypes being essential for overall resilience. The results highlight a previously underappreciated role for temperature as a key modulator of immune capacity, particularly in immunocompromised bees. The age-related differences in hemocyte abundance suggest a life-history trade-off that may prompt the increased vulnerability of honey bees as they age. This work establishes CLD as a powerful tool for insect immunology and sets a precedent for using precise immune manipulation to study host-pathogen-environment interactions.