co-opts phagocytic hemocytes for systemic dissemination in the Lone Star tick, .

Hematophagous arthropods can acquire and transmit several pathogens of medical importance. In ticks, the innate immune system is crucial in the outcome between vector-pathogen interaction and overall vector competence. However, the specific immune response(s) elicited by the immune cells known as hemocytes remains largely undefined in a and its competent tick vector, . Here, we show that granulocytes, professional phagocytic cells, are integral in eliciting immune responses against commensal and pathogen infection. The chemical depletion of granulocytes led to decreased phagocytic efficiency of tissues-associated hemocytes. We demonstrate can infect circulating hemocytes, and both cell-free plasma and hemocytes from infected ticks can establish infection in recipient ticks. Lastly, we provide evidence to show granulocytes play a dual role in infection. Depleting granulocytic hemocytes increased load in the salivary gland and midgut tissues. In contrast, granulocyte depletion led to a reduced systemic load of . This study has identified multiple roles for granulocytic hemocytes in the control and systemic dissemination of infection.