Robust Phenotypic Activation of Eosinophils during Experimental Toxocara canis Infection

Abstract

Eosinophils are multifunctional cells that have cytotoxic proinflammatory activities and stimulate CD4⁺ T-cells in experimental models of allergy and parasitic infections. Eosinophils, when exposed to antigens, are activated, expressing the CD38/CD69 molecules and exhibited increased expression of major histocompatibility complex (MHC-II), CD80 and CD86, suggesting they play a role upon <i>Toxocara canis</i> antigen stimulation. In the present study, we evaluated the profile of eosinophils using conventional and image flow cytometry upon experimental <i>T. canis</i> infection. <i>T. canis</i> antigens induced a robust activation on this subset, contributing to the immune responses elicited in the experimental model for <i>T. canis-</i>associated visceral larva migrans syndrome. Data analysis demonstrated that, during murine <i>T. canis</i> infection, eosinophils from peripheral blood, spleen, and bone marrow presented upregulated expression of CD69/MHC-II/CD80/CD86. As opposed to splenic and bone marrow eosinophils, circulating eosinophils had increased expression of activation markers upon <i>T. canis</i> infection. The enhanced connectivity between eosinophils and T-cells in <i>T. canis</i>-infected mice in all three compartments (peripheral blood, spleen, and bone marrow) also supports the hypothesis that eosinophils may adopt a role during <i>T. canis</i> infection. Moreover, <i>in vitro T. canis</i> antigen stimulation resulted in activation and upregulation of co-stimulatory-related molecules by bone marrow-derived eosinophils. Our findings are evidence of activation and upregulation of important activation and co-stimulatory-related molecules in eosinophils and suggest a reshape of activation hierarchy toward eosinophils during experimental <i>T. canis</i> infection.